Yoite
宵風Kira User / Death God / Koudou Sora
Biography
Yoite is a 16-year-old Kairōshū ninja who uses the forbidden technique Kira. By sending the user's ki into another person's body, Kira can damage or destroy the target from within, but each use consumes Yoite's life force and gradually takes away the five senses.
Story spoilers
Yoite was born intersex and was originally called Sora, a name he never accepted as his own. His family rejected and confined him, then attempted to kill him when he was 14. After escaping, he was taken in by Hattori, trained in Kira and ninja techniques, placed under Yukimi's care and given the name Yoite. In the anime he eventually dies from using Kira, while in the manga his death is due to overusing it. The manga later restores the others' memories of him before allowing Miharu and Yoite a brief reunion, after which Yoite enters what appears to be an alternate reality where his hands are uninjured and uncovered.