Haruo Niijima is a classmate of Kenichi and Miu. Originally a member of the Newspaper Club, Niijima investigates the life of everyone, ranking people on his palm pilot. He later becomes the honorary founder as well as commanding leader of the Shinpaku Alliance (a feat he seems particularly proud of despite the fact that most of its members abuse him at every opportunity), and doubles as the organizations intelligence officer. As noted by Kenichi himself, Niijima is an adept manipulator as well as natural leader. He is also an alien, and as such has several special powers. Niijima is currently a Second year student at Koryou High School in class 2-E.
Haruo has a rather "alienated" appearance. Slightly tall for his age, he has a slim yet solid physique, sharp fingernails and gangly limbs. His facial features are somewhat demonic: a long tongue with sharp nose, long pointed ears, and teeth that switch between jagged, fanged, or even just normal. Not surprisingly, Kenichi and many other characters refers to him as a "Demon-faced space alien" or something similar. He originally sported a puddle-bowl hair cut but later allowed the back to grow sideways. At times, when he is in a state of fierce concentration, two pointed antenna will pop from the top of his head. Almost always, he wears his school suit as his "Battle" outfit. He usually wears a cloak while in the base of Shinpaku Alliance to claim his leadership and his Demon King" image. During DofD Tournament, the cloak he wore was a new flag which had a painted label and kanji of Shinpaku Alliance. When it comes to some ceremony or event, such as party held by himself and captains of shinpaku or the assault of Berserker, he has worn slightly nicer clothing than his usual school uniform.
Though Niijima was initially seen as both a comic relief character and an ambitious power-grabber, as the series progressed, it becomes apparent that he is actually more perceptive and empathic than he lets on and is an altruist at heart, with an almost paternal air of leadership towards his subordinates.
His proclaimed dream of one day ruling the world remains, but it is very clear that he prioritizes the well-being of the organization that he set up and everyone who is a part of it, even if it meant withholding from them crucial information and often resigning himself to peril for their sake. He is very adept at running away from dangerous situations, always leaving the fighting to the others, a trait which Kenichi adopted to "face" women in battle. Despite his often cowardly tactics, he shows himself to be a very cunning individual, thinking many steps ahead and planning for contingencies to the point that both the enemies and allies have complimented on his leadership skills.
He is a very sly person who watches Kenichi's progress with much interest (and keeps his information up to date by bribing Miu with anmitsu, her favorite food) and treats Kenichi as his subordinate. He is very adept at running away from dangerous situations and can even outpace the likes of Kenichi, who can move considerably fast thanks to Ryozanpaku's training, though it only works while he is running away from somebody or something.
Throughout the series, Niijima has proven to be a very skilled escape artist, having shown to be a capable swimmer (he used this method to survive a direct confrontation from Hermit), and a talented dodger (he frequently evades fighters whose fighting skills rank fairly high, and his greatest achievement yet in this regard was seen when he dodged, along with Kenichi, a direct sword strike from a master-class member of Yami's armed division while on top of a speeding truck that cleaved the rear of the vehicle in half. A fact made apparent where he repeatedly thwarted Berserker's (one of Ragnarok's top three) attempts to ensnare him by deliberately stripping his clothes piece-by-piece every time Berserker thought he caught him, and during the DofD Tournament where, after volunteering to be part of the contending players representing the Alliance (since Freya, Thor and Takeda were crippled by Shou, leaving them only with Kisara and Ukita), Niijima more than played his part where he held the captain of the opposing team (long enough for Kisara to beat the remaining opposing fighters) at bay by keeping the distance between them through the use of continuous dodging and running, along with the clever use of minor ambushes. It is also worth noting that after the fight, Niijima alone was the only person from the Shinpaku members who took part in the ordeal and got off practically unharmed.
Despite his often cowardly tactics, he shows himself to be a very resourceful individual (having once saved the Ryozanpaku dojo from certain bankruptcy after devising a legitimate get-rich-quick scheme, which a desperate Miu adopted at once), thinking many steps ahead and planning for contingencies to the point that both the enemies and allies have complimented on his leadership skills. He is also a skilled tactician, capable of coordinating the combat formations and ploys that the Alliance use at both in and out battle (such as postponing the battle between Kenichi and Chikage by convincing a classmate to invite the latter into a birthday party).
Despite the fact that he, as well as most characters, calls himself evil, he usually finds ways of helping his friends when needed, though he does so in his own odd way. As the series progressed, his character is seen developing from an ambitious and conniving opportunist to an altruistic, understanding and almost paternal leader who, while seemingly will stop at nothing to achieve his goals (and often subsequently getting a comical beating from those who simply find him and his ambitions to be annoying), is actually empathic towards those under his control, and considers their well-being above all else, even if it meant withholding from them crucial information (like not telling Kenichi that another Yomi was in the same school in the form of Chikage to prevent the two from seeking a bout with each other) and risking danger himself for their sake (as seen when he repeatedly provoked Berserker to lure him away from Ukita and Takeda) and even forfeited his team from the DofD Tournament to protect them from getting killed by Sho Kano, something Shigure said is the true capabilities of a leader. For the members of the Alliance itself, they appear to have developed genuine respect towards Niijima overtime as their unquestioned leader, even Kenichi as well as the captains, since their repetitive successes (be it victory or survival-wise) in battle have mostly been influenced by Niijima in one way or another.
While generally a hands-off non-combatant who prefers to keep his distance and coordinate attacks, if forced to exert himself in battle, Niijima usually relies on hit-and-run (mostly run) and psychological tactics to unnerve his opponents and render them more vulnerable, and lets the more powerful fighters of Shinpaku to deal the finishing blow. He has a (more or less) finishing move called "Shadowless leap from the charge", which he uses to escape by switching positions with a nearby enemy. He has amazing information gathering and analytical skills (to the point that he can quickly identify a master-level fighter in a very short period of time), which he uses to prepare Kenichi for the many battles that he ends getting tangled into with his opponents' profiles and skills. He has trained the non-combat members of his "alliance" fiercely in the art of gathering information. Niijima's ability to collect data is chillingly effective, and in some cases, supernatural, such as the bizarre "Niijima Scan" technique that enables him to absorb ridiculous amounts of unknowable things about a person (Physical, Personal, Mental, Emotional, Skill Level, all of it...) simply by observing them for a few seconds (He was able to tell that a member of an opposing group had a crush on his ally through eye contact alone). What's more, he can ring his thumb and index fingers around his eyes to literally create a digital HUD of his target's power level and killing intent, and even has a zooming function, allowing him to view from afar as though he's looking through a pair of binoculars. Apparently, his senses are inexplicably unnatural, having once detected incoming missiles locked on to their location, and even discerned the presence of soldiers hiding in the woods to the point where even a Yomi member, Boris Ivanov, commented on Niijima's sensory skills that he immediately ordered his subordinates to distance themselves away from the Shinpaku leader. During the Eternal Sunset Arc, after giving an analysis on Kajima Satomi, the Yomi leader found his evaluation so accurate that he deemed Niijima a very dangerous individual, leading to him attempting to take Niijima's life then and there.
Niijima also has a talent for both tinkering and programming, having once constructed a working desktop computer from spare parts and even created the official web page for the Shinpaku Alliance with considerable security (as Loki found out when he tried to hack the page). He is also skilled engineer and traps master, having constructed rudimentary traps to ambush the Capoeira team captain, while at the same time running around the arena (at high speed), and even took part at supervising the renovation of the Shinpaku Alliance hideout, not to mention the traps that were stationed at Kisara's old hideout (now the Shinpaku's official base) to safeguard the place from infiltration. He is also very adept at espionage, and can occasionally be found casing the scene (with Matsui as his second aid, of course) already before the waited event takes place; he even once stole the keys to Tanimoto's house without him even realizing it (and has apparently made duplicates, granting limitless access to Tanimoto's property indefinitely, much to the latter's chagrin) and, while in a drunken state, once single-handedly hijacked a cargo ship all on his own.
Perhaps his greatest accomplishment in this regard yet was the fact that he once spied on the masters of Ryozanpaku and actually remained undetected for a time, and by the time Shigure sensed his presence, Niijima swiftly switched places with one of Akisame's training dummies, allowing a clean escape. He can even hide his presence from people by pressing his body against a shadowy area, using his bizarre alien abilities to render himself undetectable (though exactly how this works can be anyone's guess). He seems to have access to hammer-space, since he has been known to pull out convenient items (i.e. pepper sprays, striking batons, and of course, his prized PDA) from under his clothes.
Niijima is also very perceptive, and has, on several occasions, perceived minor details that Kenichi himself overlooked. His potential tempted Fortuna enough to try to convert him into one of his children even though he only takes kids with the potential to reach master class. And as stated by Kenichi himself, Niijima has a natural talent at manipulating people (either through persuasive language, or even blackmail, etc), which would explain how he was able to form a prominent group of diverse martial artists like the Shinpaku Alliance. He also has a problem entering churches and other sacred places, as seen when he tries to enter the church where Loki had Kenichi's sister captive and becomes weakened to the point where he must be carried. As he was being, carried his shadow could be seen struggling and screaming, and his body smoking. He's also somewhat cowardly in situations where he has to defend for himself, as he typically has to rely on other Alliance members to protect them. Niijima seem to feel kinship with those who can read/predict other people thoughts as he called Tirawit Kōkin a fellow mind reader.
Expert Evasion: One of Niijima's more outstanding skills besides information-gathering is his ability to cleanly evade incoming attacks; and while this often comes off as rather comical, he has been known to successfully dodge maneuvers and the like with consistent succession. In recent chapters, he displayed some skill in Ukemi (Art of Breaking Fall), seen when he used his own body to cushion Freya’s after the two of them got thrown off a speeding vehicle.
Enhanced Speed: Though he had never received any formal training, Niijima is very adept at running away from dangerous situations and can even outpace the likes of Kenichi, who can move considerably fast thanks to Ryozanpaku's training.
Enhanced Flexibility: Niijima displays considerable flexibility of the body to the point where he frequently shows being able to dodge attempts at his life from fighters below Master-class throughout the series; occasionally, he would end up stripping his cloths piece by piece to slip away from attacks, as seen during his “battle” with Berserker (one of the top fighters of Ragnarok). Most of the time (particularly in the manga), his near-inhuman flexibility is displayed with him being able to contort himself like a snake at high speed, effectively slipping out of any lunges or holds that opponents might use against him. This attribute has served him particularly well from time to time. Most notably “against” the Capoeira Team Captain during the DofD Tournament.
Expert Swimmer: Niijima has considerable skills as a swimmer. In fact, one of his main ways to avert danger is by diving into a large body of water nearby (this happens often) and even managed to survive a direct confrontation against Hermit (who still was not a Shinpaku captain at the time). His skills in this area led to his nickname the “Kappa”. During the camping arc, he ranked fourth, after Ethan, Kenichi, and Boris.
Limited Telekinesis:Niijima has been shown to control extrasensory abilities, such as in Kenichi's fight against Ryuto Asamiya when he causes Kenichi's belt to catch on a pipe so that he doesn't fall down.
Sleight-of-Hand: Niijima has also has some talents at pick-pocketry, having once stolen Tanimoto’s house keys without him even realizing it (apparently, he’s made dozens of copies of it ever since, allowing unrestrained access to Tanimoto’s house much to the latter's chagrin).
Enhanced Senses: Niijima apparently has a keen sense of hearing, evident by his pointed ears. With this, he once detected the presence of Boris Ivanov (who was cleaning the windows) before Miu and Kenichi did. In the Okinawa arc, Niijima said he could smell the presence of electrical devices.
Self Preservation: Niijima has been shown to have self preservative skills that have been ranked as being very near master class. This skill is shown in his speed when running away from adversaries and also in his evasion of enemies to such a level that he can even evade Master- class fighters, and master level attacks.
Coat: Niijima's coat contains an assortment of items, it contains rope, a grappling hook, 2 cans of pepper spray and a personal defense taser, along with a baton. How he fits all this there confuses Kenichi and therefore got dubbed a portal to another dimension by him.
Alien Sensors: Niijima's antennae can act as radar of sorts, that operates by erecting from the top of his head and then twirling excitedly around; with this, he has been known to detect incoming danger long before anyone else around with him can. Apparently, his alien-like senses are inexplicably unnatural, having once detected incoming missiles locked on to their location, and even detected the presence of soldiers hiding in the woods to the point where even a Yomi member, Boris Ivanov, commented on Niijima's sensory skills that he immediately ordered his subordinates to distance themselves away from the Shinpaku leader.
Concealment: By leaning against a shadowed corner, Niijima can hide his presence from nearby foes (and even innocent by-passers) for as long as he does not move. This was first seen being used to hide from Kisara and her Deputy after they finished confronting by
Suspicion radar: When someone nearby are up to something suspicious a pointy tip of hair rises from his head, This skill sometimes even reacts to his own suspicious behaviour, an example is in e32 when he convinces Ikki to join the Shinpaku federation meeting, the pointy tip of hair appears as he use dirty tactics to convince Ikki to join.
Leadership Skills: Niijima is able to inspire members of Shinpaku to meet a certain goal, and is able to convince others to accompany him to his advantage after convincing them shortly. The other non-fighter members of Shinpaku openly refer to him as their leader, in contrast to the fighter members.
Technical Expert: Niijima designed the waterproof case of his palm pilot by himself. The pilot itself seems to be unbreakable even by someone as strong as Kenichi.
Skilled Tactician: Niijima is able to position Hermit and the members of Shinpaku in strategically advantageous situations in their battle against Fortuna.
Expert Programmer: Niijima personally trains the non-fighters of Shinpaku to gather information, efficiently using digital technology to achieve this means. His programs are so strong that not even Loki, who is an expert himself, can hack into the homepage of the Shinpaku Alliance. Even Koetsuji complimented his skills, asking him for help in hacking the Okinawa Yami database, which Niijima does easily.
Master Manipulator: As stated by Kenichi himself, Niijima has a natural talent at manipulating people (either through persuasive language, or even blackmail, etc), which would explain how he was able to form a prominent group of diverse martial artists like the Shinpaku Alliance. He is even able to go as far as to manipulate the very nature of probability itself by placing his palms together, but only luck will decide if his wish will be granted. Perhaps his most impressive feat in this regard is the fact that he can, through the use of mere deceptive words, cause Chikage Kushinada to switch into her "child mode" to the point where she seems to be deliberately willing to follow Niijima's commands.
Espionage and Information Gathering: One of Niijima's best talents is in the art of spying and information gathering and can occasionally be found casing the scene (with Matsui as his second aid, of course) already before the waited event takes place, ready to extract as much valuable information as possible. He also took care to humiliate Chikage's intellect by correctly "guessing" all of the food she has for lunch. Niijima's worth and skill in this field was proven during the Eternal Sunset, as he was asked to participate along with the rest of the Shinpaku Alliance in disarming the military base. Also during the Eternal Sunset, Niijima used his "Niijima Eye" technique to gather personality traits and other sensitive information about Kajima Satomi, and not only was he surprised by the accuracy of Niijima's evaluation, but he was impressed/angered up to the point where Kajima openly says that Niijima was more dangerous than he looks, and that he'll definitely kill him.
Musical Aptitude: Niijima exhibits some expertise in the use wind instruments. So far, he has shown to be capable of playing both the (wind-based) accordion and the flute rather well. It is worth noting that this aptitude is what garnered him the loyalty of the former Fifth Fist of Ragnarok, Siegfried (who due to his personal interests, found kinship in Niijima). Apparently, Niijima can summon Siegfried from practically anywhere through the use of such instruments (even from as far as Tibet).
Niijima is first seen mocking Kenichi about his weak demeanor and how Daimonji is going to crush him in their fight
coming up. When Kenichi tries to ignore him, Niijima steps on him and kicks him continuously stating he should listen to his words and says from his information about how strong Daimonji is and mocks Kenichi for not having any special talent. After Kenichi defeats Daimonji, Niijima spreads the word around school and has Tsukuba, the strongest fighter and head of the karate club, interest to fight Kenichi, causing Kenichi to become terrified and angry at Niijima. Though Kenichi lost the first fight, after training, he defeats Tsukuba, causing Niijima to notice how much stronger he's gotten in such short time and warns him about Ragnarok how their targeting him now.
Niijima spreads news of Tsukuba's defeat at the hands of Kenichi which causes Ragnarok to draw their attention towards him. Because of Niijima, Valkyrie ordered her three best men, Taichi Kōga, Kōzō Ukita, and Ikki Takeda to find Kenichi and bring him to her. Kenichi would hide with Miu and eat lunch secretly till he was strong enough, but Niijima always found him and ruined his time alone with Miu. He would however give him stats on all three of them in an effort to warn him of their strength.
After Kenichi loses at the hands of Shinnosuke Tsuji, Niijima spreads the news around school again, which causes having more delinquents chase after Kenichi and Kenichi lashing out at Niijima again.
Niijima would hear of Kisara becoming one of Ragnarok's eight fists and would warn Kenichi about her. He also spreads bad rumors about Tsuji which makes his underlings desert him giving Kenichi a chance to engage him in a rematch.
That night, Niijima witnessed a fight between 50 gang members and the Eight Fists of Ragnarok. The leader had only Valkyrie fight them all with just Hermit and Loki assisting her to test her skills. The 50 men were quickly defeated by the three fists showing their power, greatly shocking Niijima. The next day, Niijima didn’t want Kenichi to see Tsuji again after news about his defeat being spread causing all but two of his men to leave him. At night, when Ukita and Takeda were giving a beating for leaving Ragnarok, Niijima would arrive and save Kenichi from getting stabbed. He caused the Ragnarok members to leave and shouted out the creation of the Shinpaku Alliance, causing Kenichi to be irritated by Niijima creating a gang of his own.
At school the next day, Kenichi wants to talk to Niijima about the Shinpaku Alliance flag. Niijima wanted Kenichi to join, but the latter refused. After school, Niijima and the Shinpaku Alliance bumped into Hermit who asked who trained Kenichi. Niijima didn’t know, but Hermit attacked them thinking he was lying. Niijima escaped through the sewers with one of the men from Shinpaku who was thrown in by Hermit earlier. Niijima followed Kenichi and Miu to Ryozanpaku dojo to see who was training Kenichi and thought Kenichi was living with demons and was tied up by Shigure and Apachai. When Kenichi had rumors about him beating up school members, he angrily asked if Niijima spread them, but Niijima admitted he had nothing to do with it. When they both heard of Kisara wanting revenge on Miu and planning to ruin the play Miu is in with Tanimoto, Niijima says this is perfect for Kenichi since it will get ruined and their will be no kiss scene. However, Kenichi stopped them due to him knowing how much this play means to Miu. After the play, Miu would tell Kenichi that she new he was protecting the play from Kisara due to Niijima telling her what happened, prompting Niijima to wonder if he really is starting to think of Kenichi as a friend.
When Niijima and the other alliance members were at a restaurant to eat (and show off themselves), they were surrounded by Loki, the 4th fist and began holding off his clones till Kenichi, Ukita and Takeda arrived and saved them. The three stated they were hear for a date only to be fooled when Niijima was their date and the three angrily gave chase to beat him up while Niijima was dressed like a girl. After Kenichi returned home from Chinatown, Niijima would arrive at the dojo to warn him about Siegfried, the 5th fist, who’s like a zombie by getting back up quickly no matter how many times he gets knocked down. Kenichi again refuses to help Niijima though the Ryozanpaku masters are interested in a fighter like that. At night, Niijima was spying on Loki and Siegfried only to be caught by Loki’s sidekick, Number 20. However, Niijima harassed her by grabbing her boobs and escaped. Siegfried followed Niijima even after he was seemingly defeated. Niijima reached the sewers, but Siegfried captured him. Niijima was left in a crate that was set to leave on a ship that was leaving Japan for a few days. Niijima told Loki that Kenichi would come to save him, but Loki said their was no way Kenichi would since Niijima was the worst bully towards Kenichi and getting rid of him would actually help Kenichi, leaving Niijima surprised realizing he was right. However, Kenichi did show up to save him but was too late as the ship already left. He was on the ship and caused trouble due to him dressing like an alien and scaring the crew to jump ship. On a beach, Niijima was confused about where he was, but it was known he won't be back to Japan for a while. After a few days, he would return to Japan and seemingly brainwash Ukita and Takeda into joining the Shinpaku Alliance with Kenichi showing him about a website he made for them. Niijima created a website for the Shinpaku Alliance and surprising got a letter two days before registration. It was from Loki who showed he has Kenichi's sister Honoka hostage and they all rushed over to save her. While Kenichi made it to the church, Niijima and the others with Miu were held off by Loki's subordinates and Niijima was putting up a great fighting stance only to run away. The other three easily took down the 7 Loki's, but they were all fakes just to slow them down. They arrived at the church but Ukita had to carry Niijima due to his "sickness" around churches and Ukita knocked him out due to annoyance.
Due to Ragnarok having kidnapped Honoka like that, Niijima convinced to fight the 7th fist Thor in a pit club being run by Ragnarok’s seventh fist, Thor. Kenichi didn’t want to do it, but Niijima told him that if he doesn’t attack first then an event like Honoka’s kidnapping would happen again, prompting Kenichi to agree with him for once. They arrive and Niijima helps hold off the lower thugs while Kenich fights Thor. After Thor is defeated, Niijima tells Thor that Kenichi wasn’t a subordinate, he was his "bad" friend. Thor remembered his friendship with Siegfried and knew that's why he left. The Shinpaku Alliance carried Kenichi home for his victory against Thor.
With Ragnarok having lost half of their fists, Niijima tried to convince Tanimoto to join the Shinpaku Alliance, but was turned down. So, he had Siegfried disguise himself as Hermit (due to Niijima having stolen his locker key and his outfit) to fight Loki's thugs and spread that Hermit had joined the Shinpaku Alliance. Siegfried stated he joined due to Niijima influencing him with his music. Tanimoto continued to turn down the offer despite Siegfried stating he will join eventually. Later, at Kisara's hideout; Niijima, Takeda, Ukita, and Siegfried came to invite Kisara and her gang to the Shinpaku Alliance. Niijima threatened her with photos of her with cats, but Siegfried destroyed them, since Siegfried believes blackmail is evil. Siegfried offers to let Kisara play with his 200 cats at his mansion if she joins. Kisara decides to join the Shinpaku Alliance to fight against Ragnarok. Niijima warns her that Berserker plans to attack the Shinpaku Alliance. Niijima later throws a party for Kisara joining, however, he leaves the captains' party and arrives at the underlings’ party only to see them all massacred by Berserker. He tells Matsui that now is the time for a counterattack. He arrives just in time to save Ukita and Takeda from getting killed by Berserker and lures him away into a trap, but Berserker gets out of it. Niijima is saved at the last second by Siegfried and Niijima escapes in time. At their hideout the next day, Niijima sends Kenichi a message, seemingly telling him to return home since they needed him. Koga later arrives and gives Niijima his favorite drink. However, Niijima becomes aware that he is a spy for Ragnarok, noticing that the bottle had already been opened and that he had contaminated the drink with laxative. In spite of their best efforts, Ragnarok had already found their base. It is then revealed that Niijima's message to Kenichi had, in fact, been a "will," thanking Kenichi for showing him that people could change and revealing to him the dream that he had. He also urged Kenichi to concentrate on defeating Ryuto, and that everything was fine at home. When Matsui asks Niijima if Kenichi would make it back on time, he hesitates to answer completely. However, Matsui is able to discern what Niijima really told their captain, and agreed that they couldn't tell him to return to such a dangerous situation. History's Strongest Disciple Manga, Chapter 129 The Shinpaku Alliance then try to escape from the rear when the hideout is suddenly set on fire, but a wall of fake Lokis block Niijima and Matsui’s path. They are saved by the arrival of Thor, who claims to have decided to join the Shinpaku Alliance. Hermit also arrives, stating he is only there to get revenge on Loki (though he really did want to help save the alliance). Odin and Berserker appear shortly thereafter, easily defeating Loki's new 8 Fists, and set their sights on Niijima and the others. Luckily, the heroes are saved by Kenichi's timely arrival to the fight. Niijima watches Hermit fight Berserker and is horrified how Berserker fights and uses his broken arm to attack. Niijima then watches Kenichi fight Odin and is shocked how much stronger Odin and his fighting style is, thinking Kenichi can't dodge his moves due to Odin's inner eye. He hopes Kenichi doesn't die from fighting Odin, and briefly assists him when he almost falls off the pipe they are fighting on. When Kenichi eventually wins the fight, Niijima expresses amazement. Following this defeat, Ragnarok is disbanded and the Shinpaku Alliance claims victory.
With all of Ragnarok defeated, Niijima took over Kisara's old hideout and turned it into the new headquarters for the Shinpaku Alliance after he threatened to tell people that Kisara spent 8000 yen trying to get a stuffed cat toy. Kenichi was just watering flowers around the hideout and thanked Niijima for fixing the water supply (much to Niijima’s chagrin). Niijima then announced that with Ragnarok’s destruction, more teams were appearing though most were destroyed by the mysterious YOMI. Siegfried heard that the gangs were defeated by just one person and Kisara thought that the Shinpaku Alliance is saved for last making Kenichi a target. Later that night, Niijima and Matsui were witnessing how one person from YOMI defeated an entire gang. It was a female in a jumpsuit wearing a helmet and mask and she defeated the gang in a spark (which was like a flash) then disappeared. Once the Shinpaku Alliance headquarters was finally complete, Niijima starts celebrating with Kisara, Ukita and Takeda but was short-lived when he heard that Thor's place was attacked by a YOMI member. He went to go find Kenichi and bring him back but Niijima heard from his cell phone that the hideout was under attack by Spark. Kenichi, Miu, Renka, and Niijima rushed over as fast as they could to rescue their friends. They arrived and Kenichi started fighting the mysterious Spark who is revealed to be a YOMI member Kenichi already met named Li Raichi. After Kenichi defeats her, her father, Li Tenmon, who was watching the whole time, starts attacking the alliance members. Niijima scans him and tells them all to run since he is as strong as Kenichi's masters. He tell everyone to get inside the hideout. Inside, Niijima ordered them to close the gates even though Siegfried and some of the underlings were still outside only for Tenmon to crash in through the wall. Kenichi wanted to surrender himself, but everyone (except Niijima) was willing to die with Kenichi. They were all saved by the arrival of Kensei Ma.
With the alliance having heard of YOMI and now Yami, Niijima told everyone that while Ryozanpaku is against Yami, Shinpaku Alliance will declare war on YOMI. When Takeda realized he was the only one getting normal training, he decided to ask Niijima if he knew a master on boxing. Niijima told Takeda that Siegfried went on a trip to Tibet, who the latter thought he’ll find a master. He also told him that Kisara is training with Freya while Ukita is visiting his old master. Niijima informed Takeda that he needs to find his own sacred place to improve himself. At night in an alley, Niijima tried to get Freya to join the Shinpaku Alliance, but she nor the Valkyries don’t fight delinquents anymore. Niijima decided to help her master her Jojutsu skills by having her fight against real martial artists with the Shinpaku Alliance. Takeda showed up with his jacket off and the tire worn down while carrying the two rare sea creatures he found at sea. Niijima informed Freya that everyone in the Shinpaku Alliance is getting stronger making her rethink her decision. While Kenichi was hiding out at Tanimoto's house due to him wanting to take a break from training, Niijima showed up and told Natsu that he told Kenichi, since he didn’t want important piece gone. Niijima then gave Natsu some info about Sougetsu Ma’s whereabouts. Natsu read that Sougetsu had been hired by the Red Hill Prison Group of the Chinese Mafia. Niijima revealed two members of YOMI: Sparna also known as Shō Kanō (who Kenichi still hates for kissing Miu on the cheek) and Boris Ivanov (who Natsu knows is in the city).
On a snowy mountain; Kenichi, Miu, Natsu Tanimoto, Niijima, and the first year students were there on a field trip. When Miu and Kenichi went missing, Tanimoto told Niijima that he thought YOMI was in the mountain when he an Niijima saw Kenichi’s and Miu’s snowboards abandoned. Natsu and Niijima left the lodge to search for the two missing students as well while the former was giving the latter info on Radin. As Kenichi was becoming overwhelmed by Jihan's men, Tanimoto and Niijima arrived to save him. While Hermit was defeating the servants with his Chinese Kempo, Niijima saved Kenichi by throwing a snowball at Radin (which actually had a rock in it). Niijima stopped some of the servants by hitting them snowball covered rocks. When Kenichi fell off the ski lift, Natsu and Niijima found Miu and took her out of their to save her from her fever despite Niijima wanting to go looking for Kenichi. In the morning, Niijima came out of his bivouac that he made from snow. Kenichi, Miu, and Natsu also came out and were found by the principal and Miss Ono.
When Ryozanpaku was going Bankrupt, Niijima gave Kenichi and Miu an idea and decided to let some children experience fighting for profit.
When Kenichi was given an offer to fight in a tournament on a island called the Desperate Fight of Disciples (DofD), Niijima heard the whole thing and managed to get away from Shigure for once and informed the Shinapaku Alliance about the tournament. At the ocean, Ryouzanpaku was about to leave until the Shinpaku Alliance (minus Hermit and Siegfried) came to attend the tournament as well, Niijima said the tournament was also a battle between YOMI and the Shinpaku Alliance and a way to make the world learn about the Shinpaku Alliance. The elder had cut a line on the dock and told them that the masters may not protect them all before jumping on the Sekitoba refusing to let them get hurt. Hermit arrived on a boat telling everyone that the line made by the elder was a sign for those who are willing to cross the line are ready to risk their lives. The Shinpaku Alliance headed got on Hermit’s boat and chased after Ryouzanpaku. Once the tournament starts, a big Shinpaku Alliance logo showed up on the screen meaning that Kenichi’s friends somehow got on the island. Niijima and the underlings (with their faces hidden with the logo) demanded to be entered in the tournament as well. Diego found them behind the monitor forcing the Alliance (Niijima, Takeda, Ukita, Kisara, Thor, and Freya) to come out of hiding. Sakaki punched them all (an extra hard one for Takeda who tried to dodge it) in the head for not listening to the elder. Diego came with a bad tone, but liked the Shinpaku Alliance for putting on a great show and allowed them to enter. Later, Niijima informed Kenichi how Hermit's boat blew up and they couldn't find him. However, they know he is still alive somewhere on the island. On the first day of the tournament, the Shinpaku Alliance was pitted against the Black Force Team. Mizunuma was determined to fight and win only to be defeated and Niijima said he did well and would use his defeat to motivate them to win. Eventually, they win the first round. After the first day, Niijima explains to Kenichi about the other teams that won while he was out cold from winning his match and warns him he and Miu will be facing Garyu X (which is really the elder in disguise). When Sho tried to kidnap Miu he seriously injured Takeda, Thor and Freya making them unable to fight for the second day so Niijima decided to fight with them tomorrow. Though he offered to fight, Niijima was scared how only he, Kisara and Ukita were left to fight, but Ukita told Niijima that he will keep fighting no matter what. In the ring, the Capoeira Team danced while waiting for the Shinpaku Alliance. Niijima, Ukita, and Kisara showed up for the fight. Niijima decided to join in the fight to devise some strategies more effectively. Niijima scanned the Capoeira Team for info and found out which one’s the captain and that one of them is in love with Aisha (the female member). Niijima created the SFI Plan which involved Ukita giving up his life. Kisara didn’t Ukita to do it, but after Niijima whispered something in Ukita’s ear making him determined to go. Niijima announced that the SFI Plan had failed only to get Silvio to chase after him. Niijima kept taunting the hot headed kicker about how he’ll never be as good as his leader to get Aisha. Silvio was about to kick Niijima off the edge, but Ukita managed to get back up and throw Silvio into the mote, thus eliminating him. Niijima explained the SFI Plan means Death Pretend Return Plan. Luckily, Siegfried arrived from the sky and started to dominate the Capoeira Team by defeated two members and Ukita was able to throw one out of the ring. However, due to Ukita's will to not give up and Kisara developing her Nyakwondo and Niijima instructing them how to fight, they won the match. After Sho was the one who would have to fight the Shinpaku Alliance next, Niijima, knowing Ukita and Siegfried were unable to fight anymore and Kisara was exhausted, he stepped and forfeited the match for his team knowing that they will lose. Kisara complained about Niijima’s decision, but Kenichi said that he will fight for them and Shigure explaining that retreating in a no-win situation is the best idea and that Niijima made a wise move. Just as the Shinpaku Alliance was trying to leave, all of them (including the injured members) were surrounded by Fortuna. He wanted Kisara, Freya, Takeda, Thor, Siegfried, and Niijima as his children. Kisara went for a kick, but Fortuna caught her to measure her strength showing that he was a Master Class Fighter. Luckily, the injured fighters got back up and Siegfried rescued Kisara to fight in what Siegfried called a Concert of Friendship. Niijima didn’t want them to fight fearing they’ll just replay the event of fight against Chisouken, but they didn’t care. Niijima realized Fortuna is a master class opponent and wondered how they can get out of this and luckily Hermit arrived alive and well and joined the fight. Niijima suddenly thought of a plan with Hermit put into his plan, but Hermit wanted to battle him alone. Eventually all of them were in tune with Niijima's plan by having all the fighters attack at once for more damage. Hermit didn’t want to do it, since the others were injured, but Niijima told him that they’ll still fight to the end. With their combined efforts, Fortuna was defeated and Hermit said Fortuna was really just "garbage" master class. They all watch Kenichi's fight with Sho and just as Kenichi is down, Niijima and the others yell on the screen for him to get up and defeat him. He gets up and Sho is defeated and the alliance celebrates. With everything finally calmed down and Fortuna defeated, everyone goes home with Kenichi the victory of the tournament.
As the new school year starts, Niijima and the other members are shocked to see the new school transfer students are none other than YOMI members Boris Ivanov, Tirawit Kōkin (Narashima), Rachel Stanley (Castor) and Ethan Stanley (Pollux) as second year students. After Kenichi had a run-in with Boris while on a mission, Niijima used Hermit’s scouts to investigate the YOMI students. He then told Kenichi to come to the Shinpaku Alliance Meeting and bring Miu with him. Niijima informed Kenichi that YOMI believes the Shinpaku Alliance is now part of Ryouzanpaku, since they tried to invite them (except Ukita) to join them. The captains remembered that Kajima Satomi warned them that if they don’t join YOMI, they will die. At school, the students were participating in the Sports Festival as all students were prepared to participate. Niijima was informed by Takeda and Kisara that if they don’t respond to YOMI today, they’ll die. After the festival, Daimonji ran into the alliance and told them and Niijima about Kenichi fighting Kokin and they ran back for him and Niijima was horrified that Kenichi's heart wasn't beating and did everything in his power to bring him back, even trying to do CPR (and a move he called the Devil's Kiss). After Kenichi got over his fear of death from his near death experience, the school went on a camping trip with everyone. In a swimming contest, Niijima came in fourth. At the mountains; Kenichi, Miu, Niijima, Matsui, and Kurokawa were in one group on the B Course thinking Boris wasn’t going to reach them until the summit, but Boris had ambushed them. Boris attacked them with log and threw Kenichi with him off the cliff. Miu and Niijima had to fight off Boris's men while Niijima warned the other members about the attack. As they were surrounded, Niijima played his flute to summon Siegfried and help defeat their enemies. Once Boris was defeated by Kenichi, he returned home after the camping trip to find his master leaving only two members of YOMI left in school (which Niijima explained was because Kokin left not being able to stay since he tried to kill Kenichi). Later, at Shinpaku Headquarters, Niijima was informed that 5 YOMI members had entered Kouryou High School by former Ragnarok members Loki and Number 20. Four of the YOMI members they saw were transfer students, but they didn’t check that any of the freshmen was the fifth YOMI member. That member is named Chikage Kushinada and only Niijima, Miu and Kenichi knew this but choose not to tell anyone yet. When Chikage is seen talking to Kenichi about plants, Miu is worried she may attack Kenichi but Niijima says it's fine and that he’ll try to lure her away from him, but Miu warned Niijima that child shouldn’t be underestimated. When Kenichi decided to eat lunch with Chikage, Niijima ate with Miu much to her displease since she wanted to eat with Kenichi. Niijima tells her that Chikage was a young genius in every way.
When Renka would transfer to Kenichi's school, Niijima would offer her to join the alliance only for her to attack him wanting to be in charge, though she would calm down when Kenichi asked her to. At a cafe, the Shinpaku Alliance (Kenichi, Miu, Niijima, Takeda, Ukita, Kisara, and Renka) treated Chikage to some sweets on Ukita. Chikage was about to show her emotions when the sweets were ordered until she got a call from Mikumo to attack some martial artists. When Takeda offered to have a friendly rematch with Kenichi, Niijima and the others would watch and be amazed how far Takeda had come since their time together.
When Chikage gave Kenichi an invitation to fight him, Niijima and Siegfried helped keep her busy buy luring her to a birthday party with cake and karaoke to Kenichi wouldn't have to fight her. Back at school, Niijima told Kenichi why Chikage didn’t come to fight which relieved them. Niijima was about to show everyone the embarrassing photos until his camera was crushed by Ethan though he gave Niijima money back for the broken camera.
After Ethan went home, Niijima would inform Kenichi about how he’d identified 9 members of YOMI from Loki who slipped into YOMI’s ranks. But the tenth member seems to be a mystery. The next day at school, Niijima found out from Loki and Number 20 that the 10th master of Yami is Sougetsu Ma meaning the last member of YOMI is Hermit. Later, he would invite Chikage to the festival by the latter telling her about the sweets. Later, at the Shinpaku Headquarters, Niijima was announcing the weapons battle is soon approaching while Kenichi, Miu, Ukita, and Siegfried were playing cards while Takeda and Kisara were practicing their skills. Thor informed the Shinpaku Alliance that Freya and her grandfather were kidnapped by Yami. Yami threatened them that they must join their army if they want to see Freya and her grandfather return safely. The Valkyries needed Shigure’s help in case a fighter or weapon user of master class shows up. Niijima told everyone about the GPS in Freya’s cell phone to locate her. Outside the building, Niijima had a hard time figuring out how to get in without the police coming to arrest them until they saw Shigure knock out the guards with tranquilizer darts and Touchmarū disable the cameras. When they were about to go in, Niijima tracked that Freya is outside. As the truck with Freya and Danki drove away, Kenichi chased after it while Niijima was with Freya and Danki. Niijima helped Kenichi get on top of the truck, but they were seen by Koukin who’s driving a car and both attacked by Yami’s Bantou Master. Niijima and Freya rolled out of the truck and on the streets escaping Yami, but an injured Kenichi and a clueless Danki were still on it. Niijima and Freya reunited with the other telling them that Kenichi has been cut, but Shigure informed them all that Kenichi will survive. They arrived later to see the enemies defeated and Kenichi having won thanks to Danki.
Okinawa Arc 
At school one day, Niijima would inform Kenichi that one of the Yami bases is located in Okinawa and that Agaard Jum Sai of the Nine Fists is there. When Kenichi and the others traveled to Okinawa to assist Ryozanpaku in their fight against Yami. Later that night, while Niijima makes sure they can't get through the floor of the hotel, he is unfortunately taken by Apachai and taken to the Okinawa base with Kenichi. He and Kenichi would be left speechless as the elder use a move they said is like a blast and wonder how can one man do something like that. Once Kenichi, Niijima, Miu and Apachai reached the top floor to where Agaard and Kokin were, Niijima would scan Kokin and and saw that Kenichi won’t win. A blackout occurred when someone hacked into the system, but it didn’t slow him down as the battle started which changed the flow of battle. However, Kōkin let Kenichi answer his cell phone when someone was calling him. Akisame called Kenichi to have Niijima go to see him at the computer room on the third floor to collect data and take Miu with him. Kenichi told them that he’ll win before the battle truly started as Miu took down the guards in their way while Niijima prays for Kenichi not to die. Niijima was trying to find the computer until they were attacked by the swordsmen. Miu threw Niijima into the computer room she found so she could fight at full power. Akisame wasn’t good at hacking into computers to turn back on the computers, but after seeing how Niijima does it he was able to copy his methods. Niijima took out the hard drive as Akisame put it on another PC. He arrives later to be horrified on how injured Apachai is and how they managed to save him while he says to himself how scary Ryozanpaku is.
After the Ryozanpaku masters have to leave for being framed for something they didn't do, Kenichi informs everyone of the situation and Niijima decides the Shinpaku Alliance should help so they could shine. Niijima called Siegfried, Freya, and Thor about the news. Niijima then brought Chikage Kushinada along to have her fight one of the members of Yami without realizing it by forming a detective gang. Niijima explained to Takeda, Kisara, and Ukita that Ryouzanpaku has been framed, since the Anti-Yami faction of the government has been controlled by the Pro-Yami people in the government. The six students arrived at Inspector Honmaki’s place when he called Niijima, but heard that the inspector was being attacked. They ran over and saw he was attacked in the backyard by some Yami Weapon Users. In a hotel, Niijima unplugged everything and had Honmaki’s daughter close the curtain so Yami wouldn’t see or hear anything. Honmaki explained that the Yami faction of the government lured Ryouzanpaku to Okinawa to frame them. Niijima then revealed he had a backup disc copied from the hard disc from the base stating he would never allow such precious data to go to waist. On their way, they were attacked by the Yami weapon's division and barely escaped into the mountains. Niijima spot some vehicles following them so Kenichi wanted to act as a decoy. But, Niijima sensed a traitor among them which was a transmitter planted in the charger of Honmaki’s cell phone meaning that Yami heard everything they said. Niijima had Takeda and Kisara follow him to Ishida while everyone else had to stay behind as decoys. Niijima’s group finally reached Ishida’s place in the villa only to come against some more monks that have captured Ishida. Takeda and Kisara prepared to fight against armored monks to show their power. Niijima sensed Rimi coming so he hid his presence. Rimi body searched Takeda and Kisara in an instant then did the same to Niijima when one of the monks revealed Niijima’s location and got the disc. Luckily, Miu caught up to Rimi to take the disc back. When Miu knew Rimi was from YOMI, Rimi accidentally told her she was being trained by Kensei, she is in love with Ryuuto, and she is the leader of a group called Titan, prompting Niijima to say she's like a goldmine of information. Once Miu and Thor return with the broken disc and apologizes for it breaking, Niijima reveals he has a USB stick of the information on him revealing that he would never let information like that get destroyed so easily, prompting Miu and Thor to get angry at him and Miu would throw little broken shards of the disc at his head. Unfortunately, Ishida revealed to be a member of Yami and a master class weapon user as he instantly sliced the USB stick. Niijima found out that the data-stealing plan in Okinawa was a bait to find the Anti-Yami members of Congress. Niijima wanted to run, but the others wanted to stay to fight him knowing they would get killed either way. Luckily, they were saved by Sakaki who was watching the whole time in the bushes and helps defeat Ishida with ease. Ishida was down, but still conscious telling everyone that Ryouzanpaku would never be cleared of their names. However, Niijima revealed that Akisame told him to upload everything on the internet. As Sakaki and Honmaki took Ishida and the monks away, Sakaki congratulated the Shinpaku Alliance for an awesome fight.
After hearing Miu was kidnapped by the Demon Fist Junazard, Kenichi started beating himself up for not being able to protect her only for Niijima to hit him with a chair saying if he wants to beat himself up so much he'll be glad to but reminded him that he is not the only one worried about Miu. After Hongo gives Kenichi's masters word about where she is, the others alliance members wish him good luck They all put their fists in for goodbye except Niijima who thought was a Rock-Scissors-Paper Contest. A few weeks after Kenichi went to Tidat, Niijima and the others were assisted by Rachel due to her wanting to repay Kenichi's masters for saving her from Junazard and gives them the location of where she is in Tidat. Niijima uses his computer and tells Kenichi the location of Miu's whereabouts are.
With Miu back home back to her old self and Jenazad dead, Niijima warns the other members about how the YOMI members haven't been coming to school lately and thinks it has something to do with Jenazad's death and warns them that "Judgement Day" is near. He later has all the alliance members gather to gain knowledge about their enemies now more than ever. As he scolds Matsui for messing on the computer over someone popular as Rimi, he remembers that name and looks at the picture of her and wonders why she's on a blog sight. He becomes excited over Rimi's stupidity and tells his men to blog and gather as much data on this site as they can while calling it a goldmine of information.
Following the discovery of a Yami base, Ukita and the rest of the alliance travel to the location but are forced to stay by the masters. However, after they leave, a limo that took the YOMI members from before arrive and Berserker and a member named Lugh. When Kenichi notes Niijima knows something, Niijima reveals he got word that Berserker joined Yami as Ogata's disciple. As he sees Lugh and Berserker leave he attempts to goad Berserker to stay with multiple insults due to him sensing a bad feeling from Berserker and Lugh and because he feels that they have the advantage due to the situation and his desire to gather more information. However, it didn't work and Lugh decides to fight the alliance. Believing that since they have more in numbers Niijima sends everyone to fight, but is annoyed at Kenichi's decision to fight Lugh alone. He becomes shocked to hear from Sieg that Lugh is blind and tells him to get out of their before Lugh kills him. Niijima is then horrified seeing his neck broken only to be snapped back into place prompting Niijima to wonder what training he went through in Tibet. As Takeda fights Lugh alone, Niijima notes the stupidity that no one will gang up on him and is frustrated over their honor of fighting. As Takeda prepares to sacrifice his left arm to strike Lugh, Niijima does nothing stating he couldn't even if he wanted to, but they are both saved by Kenichi. As Lugh leaves, Niijima notes how despite martial arts being rough in his opinion, they have their honor to leave and senses his dark nature as he leaves when Shigure arrives. When she states she sensed a strong presence, Niijima notes they were lucky as if that fight had continued, Takeda might not have gotten out alive. Niijima later attends the amusement park with the others and notes with the battle of YOMI arriving some relaxing is good for others. At night, he was shocked to run into Berserker and runs away while Kenichi tells him to warn the others. He continues to run to find others to protect him only to see that everyone is fighting a YOMI member and runs into Miu fighting Rimi and notes there's nowhere for him to run. He later runs into Thor and the lower Valkyries and Matsui and warns them of the attack by YOMI. As others panic he tells them to calm down and that they need to regroup and prepare for combat (though Niijima was just saying that to make everyone not notice he was panicking). They make there way to Rachel's and Renka's fight and marvel on how there almost naked, causing Renka to attack them in embarrassment. As Niijima gloats how they saw everything, Rachel leaves believing she ashamed herself of not using flashy moves, much to Niijima's surprise. Seeing that the others fights have ended, Niijima wonders how Kenichi is holding up. He has the rest of the alliance leave the park while he and Renka go find Kenichi. They do after Niijima believes he saw someone who looked familiar leave with his family. The two find Kenichi and Miu along with Ryuto and Rimi and Niijima tells them everyone else is fine. He is then shocked to discover the person he saw was Tanaka and points out he's fine and with his family, which has Kenichi smiling knowing he was reunited with his family.
Days later, Niijima greets most of the alliance after the battles and points out how Rachel and Chikage haven't gone to school lately and Tanimoto is going to school like nothing happened. When asked about Kenichi, he says he and Miu went to see the people who got out of the darkness: Ryuto and Rimi. Several days later, Niijima gathers all of the captains at the base to wait for Kenichi and Miu. Kenichi and Miu notice that Apachai and Shigure have been waiting at the base asleep the whole time, waiting for everyone to show up. Shigure then wakes up and tells them that she has something to give them, and then takes the bag away from a sleeping Apachai and hands all of the captains the arm protectors that she made for them, then demonstrates how strong the gear is against a weapon, which amazes everyone. Later, he is informed by Miu and Kenichi of Shigure's capture by Yami, greatly shocking Niijima wondering how could someone as strong as Shigure be captured only to realize it was cause she fought 7 people on her own. Afterwards, Kenichi asks for his help to find a woman named Kiyoi Kidou through his network. After doing so, Niijima goes with Kenichi and the others to her location and discover of how her brother is a member of the Hachiou Executioner Blade and a special satellite phone that is impossible to make calls out of. However, at that moment Shigure calls Kiyoi, shocking everyone. She gives everyone her location before the phone on her end was destroyed, to which Niijima remains silent as the phone goes dead. They then leave once they have her location, to which they are approached by Okamoto again who seems to have been listening. Later, Okamoto take Niijima and the Shinpaku Alliance out to find Shigure while the Ryozanpaku masters attempt to attack the base head first. Okamoto apologizes for the situation, but notes the alliance and Ryozanpaku may be the only ones able to save everyone now, as Japan is Yami's first target. On the way over, Niijima watches as Miu and Kenichi spar noting how they and everyone else have progressed so far now, especially under Okamoto's progress as he helps spar with them as well. As Kisara complains about the tight space, Niijima sates it can't be helped since they are in a submarine in the bottom of the ocean. As they are all resting later, Freya questions Niijima about Okamoto if they can really trust him, to which Niijima also admits his doubts in Okamoto but admits he is extremely skilled. As everyone voices their concerns in the up coming battles, Niijima tells them to all calm down and remember their original purpose: using a USB drive they are to sneak into the Yami base's missile system and render it powerless. He advises them to leave the fighting to the masters as they have their own battle in this war. As Okamoto returns and tells them its time, the Shinpaku Alliance prepares for battle. After Okamoto takes out the soldiers at the bay, Niijima expresses his amazement at his skills as he and the others dock on land and enter the forest. Once they are ambushed by Yami soldiers to which the others are able to take down. Okamoto volunteers that he stay behind to defeat the rest of the soldiers as the commotion can distract Yami and allow the disciples to sneak inside the missile base. Niijima asks if he's sure about his suggestion since the outcome of the war hinges on the success of their mission; Okamoto repeats the same words that the Katsujinken masters said to the disciples ("I know you guys will come through.") and states that he'll place his faith in the disciples as well. They escape and reach a waterfall, to which Niijima note they are close to the base. However, just then they are found by the YOMI disciples. Siegfried calls out to Niijima, who tells Kenichi and Miu that they'll take advantage of the commotion and move on ahead. Kenichi rejects the idea as he doesn't want to abandon his friends but Niijima reminds him of their purpose of disabling the missile base. Niijima adds that the captains of the Shinpaku Alliance have talked about this prior to the battle and they encourage Kenichi to advance. Kenichi, Miu, and Niijima run into the forest to take cover as the other Katsujinken disciples charge in towards the battle. Once they arrive at the base, Miu and Kenichi take out the soldiers to which YOMI's leader, Kajima Satomi shows up and agrees to escort them to Shigure's location. Kajima Satomi leads Kenichi, Miu, and Niijima to the cell where Shigure is being held to find that she has already escaped. When Kajima reaches his hand out to shake Kenichi's, Niijima stops Kenichi from being so naive and and he uses his "Niijima Eye" on Kajima. He analyzes his profile of Kajima states that he senses a dual nature in Kajima, causing him to take notice and compliment Niijima. Kajima confirms that he has two masters and as he shakes Kenichi's hand he adds that he has an order from his other master: to kill any intruders. Kenichi is restrained through Kajima's handshake and Miu is attacked by Kajima's assistants. Kajima adds that Niijima is especially dangerous and that he has to be killed. Kajima grabs Niijima by the head and begins crushing his skull but he is stopped by Kenichi who manages to kick out from his position. Niijima tries to talk to Kajima as he had been ordered to get them inside the base (by Miu's father) but Kajima adds that he was also ordered by Senzui to kill them and he has been wanting to fight against Kenichi. Niijima tries to sneak away from the battles but Kajima runs past Kenichi and aims an attack at Niijima to stop him. After seeing Kajima use seals on his toes and hands, Niijima questions the authenticity of the seals, asking if Kajima is some sort of ninja to which he replies that Kuremisago was originally a ninja clan. As Kenichi and Kajima continue their bout Niijima eventually eludes them. Niijima runs through the base and makes his way to the control room but he is stopped by Saiga Furinji who asks him to hand over the virus. Niijima panics as he unsuccessfully tries to trick Saiga by giving him fake objects and Saiga comments that Niijima is tougher than he looks and he needs to be killed. As he aims for Niijima a kick blocks Saiga's arm and Hongo aims a thrust at Saiga who parries it. Niijima is stricken immobile being so close to the battle, despite his ability to ignore any situation and escape. Niijima moves his finger but an attack immediately lands next to him, causing him to marvel at Saiga for being able to notice him despite facing off against another master. Niijima is stunned by the immensity of the killing intent between the two fighters as Hongo takes a stance and prepares his technique. However, Saiga pares and easily defeats Hongo as Niijima is approached by Saiga again. Niijima is helpless as Saiga reaches out to kill him but is saved by James Shiba who was directed there by Kenichi. However, Shiba says that he did not arrive to save Niijima but rather to settle his grudge against Saiga as Saiga calmly comments that the forgotten underground boxer will die a pointless death. Saiga charges towards Shiba but the boxing master moves back and suddenly grabs Niijima. Saiga is caught off-guard as he realizes that Shiba is taking Niijima to escape. Shiba jumps 20 floors to take Niijima to the missile control room and he laughs at Saiga, saying that he intends to get back at him any way that he can, adding that revenge is about stopping your opponent's goals rather than defeating them in a fight. Shiba drops off Niijima and tells him to go on ahead as he holds back Saiga, destroying the entrance to the hallway to prevent pursuit. Niijima runs off to the control room while Shiba stays behind and fights Saiga. Niijima arrives at the control room to find it guarded, and he thinks of a plan to sneak inside. After some thought he thinks of catching the soldiers off-guard by suddenly dancing in front of them and then sneaking past them once they let their guard down. He thinks of the captains of the Shinpaku Alliance who are fighting and relying on him and Niijima resolves to carry out his plan. Unfortunately his plan fails and he is captured, he tries to negotiate for his life but the security leader ignores him and orders to have Niijima killed. As the soldiers slash at Niijima their katanas are suddenly cut and Shigure appears to rescue him. A man within the control room orders the entrance to be sealed off but Shigure blocks the closure with her sword and knocks out the people inside the control room. Niijima goes to a computer and prepares to install the virus and Shigure senses an opponent approaching, just as Saiga arrives and sees that the control room has been breached. She successfully locks the room behind them and keeps Saiga back while Niijima successfully uploads the virus. Unfortunately for him, As Saiga and Senzui (who both disguised themselves as different people) blasted their way through the iron door and destroyed the computers in that room. Niijima then panics as his virus wasn't fully uploaded and, with Shigure's and Tochumaru's help, looks for a working computer to upload the virus while Kenichi fights Kajima to keep him from interfering. An announcement says that there are two minutes left until the missiles launch and Niijima has found a computer to complete the virus upload. Shigure tells him to hurry as they have been discovered by the enemy and she is seen fighting off a wave of enemy troops. After Kajima uses Kai Shinogidachi on Kenichi, Niijima calls out to Kenichi and gives an evil laugh after Kenichi counters Kajima with his "holding" ki method and watches amazed as Kenichi defeats Kajima. After Saiga's and Senzui's fight comes to an end Niijima celebrates as he was successful in stopping the missile from launching. However, he notices as Saiga was able to get the remote detonator from Senzui and tells him to be careful. He then reacts horrified as Senzui is able to get it from Saiga as he activates it while killing Senzui in the process. As the missile is launched, the elder shows up and sacrifices himself by destroying the missile himself. Luckily, the Elder survives and the alliance later celebrates their victory as Yami officially collapses.
In the Epilogue, Niijima's business has increased largely, as he was seen in a photo with several people behind him in suits, hinting he achieved his dream of expanding the Shinpaku Alliance all over the world.
Despite not being a martial artist, Haruo Niijima has experience on the battlefield (mostly due to the fact that he gets dragged into everyone else's fights against his will and better judgement). Niijima himself has been in some situations that could actually qualify as a fight of sorts. Such examples include:
- vs. Kenichi (won) (was one of the people who bullied him all through the beginning of high school)
- vs. Kisara's gang (won) (Assisted by new formed Shinpaku Alliance)
- vs. Siegfried (lose) (was caught in a chase)
- vs. Berserker (Undecided) (with the latter trying to catch Niijima, but being outpaced, trapped, and ultimately interrupted by Siegfried)
- vs. Capoeira Team Leader (Undecided) (During DofD tournament, participated only because he had to)
- vs. Chikage Kushinada (won) (In a guessing game, although he did cheat)
- with Takeda, Miu and Ukita vs Loki's thugs (Won)
- with Kenichi, Miu, Renka Ma, Kisara, Siegfried, Ukita, Takada, and Shinpaku grunts vs. Li Tenmon (lose)
- with Ukita, Kisara, and Siegfried vs. Capoeira team members (won)
- His father is a demon and his mother an alien. They told him to go and conquer the earth.
- He has written several books.
- His ki-type is officially listed as ★ in the guidebook. Probably, because he is neither a proper martial artist nor human.
- His rank within the Shinpaku Alliance has been translated as "general" in several cases. The correct translation for 総督 (sōtoku) would be governor-general, governor, or viceroy.
- History's Strongest Disciple Kenichi Official Guidebook, page 84.
- History's Strongest Disciple Kenichi Official Guidebook, page 86.