Colonel Alexander Gaidar (アレクサンドル・ガイダル, Александр Гайда́р) is the Combat Sambo Master of Yami's One Shadow, Nine Fists, the Master of Boris Ivanov, and a former Armed Forces commander of the Russian Military.
Alexander is a tall, muscular man who has long wavy light colored hair down to his shoulders and has strangely colored dark eyes. He typically wears an artist outfit outside of battle and when he is active, he wears a dark military-themed suit with dark dress pants, white dress shoes, and a pair of white gloves. When angry his face looks more terrifying.
Alexander is shown to be capable of switching from a nonchalant demeanor to a raging man in a second, not unlike Ogata but with a lot less control. He took up sculpting and painting in order to create an atmosphere of peace to distance himself from the constant fighting. He particularly hates guns, which he refers to as "dirty metal", and if not in battle with somebody else, will kill a person who points a gun at him immediately regardless of the person's affiliation. He seems to have a lot of pride in SAMBO and tried to prove that modern SAMBO was far superior to the ancient traditional Jujitsu that Koetsuji uses. He seems to care for Boris' well being, as seen when they have a lot of conversations and disowned Boris as his disciple in order to prevent the latter from being possibly killed by YOMI.
He also happens to be quite a clean freak, constantly following after his house keeper with a mop to clean after them while they are cleaning up, but he contained those tendencies after he took in Boris.
Strangely enough, he was very certain on instructing Boris that he should always stay cool on the battlefield, because "people who lose their cool on the battlefield, die" as he says, despite being a man that loses his temper extremely easy and proceeds to destroy everything around in very frequent fits of rage. This could be due to his knowledge of the difference of their fighting styles, with Boris being a Sei-type fighter and he being a Dou-type fighter.
Alexander has shown to have some honor, as after having lost to Akisame, he willingly went to Big Lock (though he did promise he would escape someday). This promise was kept as he did, however, rather than return to Yami, Alexander kept his word to Akisame and choose to fight with Ryozanpaku against Yami.
Alexander grew up in Russia and at some time entered the army and managed to become a colonel. During this time, he took Boris Ivanov as his disciple, and Boris enlisted himself into the army, becoming a member of his unit. Later, he entered Yami and became one of the Nine fists. During this time, Alexander began a number of unidentified crimes within the military. These crimes become unknown to the Russian Military until years later by several anti-Yami factions. Like all of the other members of the One Shadow Nine Fists, Alexander participated in the joint training of Sho Kano as the sole successor of Yami.
As a member of Yami, Alexander is a very powerful fighter. Even his disciple acknowledges his strength. Being a high government official in the army gives Alexander a very powerful hold on the government, making him one of the more politically powerful members and as a high ranking army official, he has an large number of subordinates and followers. His Combat Sambo fighting style makes him very dangerous to handle as he can turn a punch into a throw or mix throwing with striking attacks into a deadly combo. A testament to his skills is that he, along with Diego Carlo, are capable of escaping Big Lock with little effort and can do so at any time they feel like it.
- Seasoned Veteran: As a former soldier and colonel, Alexander has experience in and out of a battlefield, combining his years of experience and training as a soldier with his mastery of Sambo to create a more deadly varation called Combat Sambo, making him a even more dangerous fighter and allowing him a variety of different battle tactics to use.
- Immense Strength: Able to make sculptures with his bare hands and break handcuffs without trying. He is also seen lifting one ton steel bundles and throwing them around like soft balls during his first match with Akisame. Also during his second match with Akisame the fight tore apart an entire army base. Also his strength is so great that he was able to wipe out an entire battalion of soldiers single-handedly.
- Immense Speed: Despite being a dou martial artist, he is still able to hide his killing intent and run past people unnoticed leaving only a strong gust of wind as an after effect. As a master class martial artist he can easily get around people and take out surrounding people in an instant before they can react.
- Innate Talent: Alexander is able to use numerous techniques in unison and learn new techniques after just seeing them once. Having only fought with Akisame once, he was able to learn his Yahagi Ayurashi and use it the next time that they fought.
- Immense Dou Ki: By focusing his ki he can destroy walls and other things without having to hit them.
- Master Craftsman: He paints and sculpts several masterpieces only to keep himself calm. He's also skilled in the art of music in playing the violin. His artistic skill may even be compared to Akisame.
His disciple, Boris draws with Kenichi in their duel in the Ryōzanpaku dojo. When Ogata meets to speak with Alexander about this on his submarine, he flies into a rage over Boris' manipulation into attacking Ryōzanpaku. He was later seen meeting the other One Shadow Nine Fists to discuss who will lead YOMI and who will fight Kenichi next.
First seen participating in a meeting of important people in Russia. At that time he managed to get past the
security search since he didn't carry any weapons and when he entered he heard someone mocking Yami, since they are believed to be weak for not using weapons and just a rumor. He quickly got around that person and when his guards pulled out their guns ready to shoot him he quickly switched to his raging form and took out all 49 people at the meeting in an instant. He later jumped out the window and asked Boris for some tissues. He later left to kill a congress women and managed to find her in her hotel room and escape through the window with her as a hostage. He later met Akisame at a construction site, and they both demonstrated their martial arts and art sculpting skills. He deflected numerous iron cables while at the same time he managed to make an angel with the rods in an instant and then threw his creation at Akisame, only to have it reformed into a throwing statue to catch him. He quickly switched into his rage mode and threw a number of fierce attacks at Akisame but only managed to land a single attack. Later he tried to attack again but quickly fell to Akisame's Koetsuji willow leaf walk. Realizing that he can't match Akisame's speed, he decides to retreat but not before throwing the congresswoman over the side, though failed, as Kenichi dived to save her and Sakaki managed to save both of them.
He reappears at his Russian base with his soldiers all in formation. At the time he was talking with one of his higher ranking officers, and becomes irritated at the fact that because of his raging personality, entire squads of soldiers had to be sent to his base to keep him in check. He is tricked by Akisame into spilling his connections with Yami and engages in a second battle with the Jujitsu master.
Alexander learned Akisame's Yanagi Ayurashi after witnessing it from their first battle, which Akisame said was impressive for a master of Yami. He is finally defeated by Akisame in Battle 304 when Akisame used a strangling move to counter his "March of Death" suicide technique, knocking him out for 2 seconds. Alexander surrenders to the authorities and proceeds to disown Boris as his disciple and orders him not to try and find him (in that order, making Boris ignore the second order). Just before he was taken into custody, Alexander ominously issued a warning to all who were present that they "shouldn't think it's over just like that". It is unknown at this time what he meant by this warning, but is implied to refer to the Eternal Setting Sun.
He is currently being held in Big Lock. His defeat and incarceration makes him the first of the One Shadow Nine Fists to be taken out in the ensuing battle between Yami and Ryozanpaku.
After the battle between the Shinpaku Alliance and Yomi at the amusement park and the fight between Ogata Isshinsai and Tsutomu Tanaka ended, Alexander is seen inside of Big Lock alongside Diego Carlo, with Alexander making another one of his works of art. It is then revealed that both of them can escape from Big Lock anytime they want, and that they are willingly staying there because they lost to Ryozanpaku and that their pride as martial artists makes them bound to the winners orders. They also stated that they will get out of Big Lock only when there is a good enough reason for them to leave, to which the Yami weapon user told them that the Hachiou Executioner Blade team is gathering again, a statement which intrigues them both. After hearing this the weapon user stated that the One Shadow wanted them to know this and told them to think carefully about their decision. He is next seen still inside of Big Lock, where it is revealed that both he and Diego have been sneaking out of the prison to buy various items (some of which were very expensive on Alexander's part), and then continuously returning there. Diego begins to talk to him about how his disciple, Boris was able to find the location of Big Lock and wait for his master's return, then begins to talk about his own disciple, Rachel, to which Alexander mockingly asks Diego if he was homesick. Alexander then begins to go on about how he's getting tired of his little "vacation" and says that it wouldn't be bad to go outside again to see the beginning of the Eternal Setting Sun.
During the Eternal Sunset with Yami and Ryozanpaku, Diego and Alexander escapes from Big Lock. As the battleships prepare to head out a soldier reports seeing shadows in the water as three of their battleships are sunk. A submarine surfaces with Diego Carlo and Alexander Gaidar inside, who have been guided there thanks to Boris. Both masters arrive to fight along with Ryozanpaku: Diego asks his disciple where he can stand out the most and Alexander wishes to maintain the honor his death match with Akisame and stop Yami's "inelegant" methods.
Fighters arrive to engage the two masters and Diego asks Alexander why he is fighting against Yami and he answers that if there is no beauty in the Eternal Setting Sun then it must be stopped, as he charges in and mows down a group of soldiers.
Once the Eternal Sunset is lost, Alexander celebrates with Diego.
In the Epilogue, Alexander returns to his country, and is now apparently pardoned of his crimes due his participation in stopping the Eternal Sunset. He is there to witness Boris be awarded his medal and stated how proud he is of his disciple.
- Alexander is from Russia and makes western art while Akisame is from Japan and makes eastern art. Their differences are exemplified further by Alexander's Dou ki and Akisame's Sei ki.
- He received strange vibes from Ogata and doesn't really trust him.
- He's gotten along quite well with Diego after they spent some time in prison together.
- He secretly respects Akisame for his art and fighting skills.
- He's a obsessive clean-freak and even follows his house keeper around with a mop to clean after them when they are cleaning. He's gotten a bit calmer about that after taking in a disciple.
- Matsuena thinks that he, Akisame and Siegfried would make a great music ensemble.
- He designs his own clothes (and always keeps them clean. He even carries antibacterial goods with him.)