Kiyou Kidō is Rin Tachibana's younger half-sister
Kiyoi is a young woman of average height with medium length wavy dark hair down to her upper back. She wears plain clothes and has a necklace around her neck and a cane around her wrist due to her blindness. Her eyes have no scilla due to her blindness.
Kiyoi is a rather sweet and innocent young woman despite her invovlement in the world of martial arts. She's shown to be rather bold, attempting to get by in her life by dealing with her blindness rather than relying on others. She's also rather perceptive, having deduced correctly the number of people, including by gender, were present in her home.
Her relationship with her brother is somewhat complicated, especially knowing of his involvement with Yami. Nontheless, Kiyoi has shown to love her brother very much, but wishes he would come out of the darkness.
After discovering of Kiyoi's connection to Yami through Okamoto, Kenichi, Miu, Sakaki, Akisame and Niijima go to visit her for information on Shigure.
Once they meet her and discovering of her good intents, Kiyoi Kidō begins her story and says that she has heard all about Ryōzanpaku from her brother, and that her way of thinking has been influenced by them. She is very thankful to her brother for allowing her to live a comfortable life but that is the reason why she wants him to be stopped. She receives a warning from her brother to flee the country because Yami is planning to destroy particular countries to rupture the balance of the world, with Japan being one of them.
Akisame asks if she means the Eternal Sunset and Kiyoi Kidō confirms his suspicions, adding that she wants to stay in Japan to witness everything. While she does not know the exact details of Yami's plans she knows that Rin always follows through with his words and that is why she wants Ryōzanpaku to stop him. Akisame asks how she is communicating with her brother and she answers that he contacts her with a one-way satellite phone.
Just then, she receives a call from no other than Shigure Kōsaka, the person Ryōzanpaku has been searching for. Everyone takes the phone from her in frantic to talk to Shigure, to which Shigure gives them all her location before Yami destroys it. Once Ryōzanpaku has her location they leave as Kiyoi looks on worried.