Yoite

A 16-year-old ninja in the Kairōshū who uses the forbidden technique "kira". This technique shoots the user's ki into the body of a target and controls it from the inside out, which can cause the target's bones to break or their body to completely explode. The cost of using this technique is the loss of the user's life force, gradually losing their five senses and eventually dying.

Yoite was born intersex, implied to be assigned female, and was named Sora, although Yoite never considered it to be his name. His mother died in childbirth. His parents shunned him, calling him a death god and going to great lengths to deny his existence. He was confined to the basement and his half-brother Koudou Tsukasa was forbidden to approach him. When Yoite turned fourteen, his family decided to kill him, slashing his throat and unsuccessfully forcing Koudou to do the same. After this attempt on his life, being erased from existence became his goal. He ran from the house and was saved by Hattori, who accepted him into the Grey Wolves.

Yoite spends a year studying the Kira technique and all required ninja skills. Hattori promises this would bring him closer to his goal of being erased. Yoite is placed under Yukimi's care and is given the name Yoite. In the anime, Yoite expires in the last episode from the use of Kira. In chapter 50 of the manga, his death was also due to the overuse of Kira, just seconds before Miharu activated the Shinrabanshou and erased everyone's memories of Yoite. However, from time to time, when they face with what would have been a memento of Yoite's actions in the past, some characters' memories are still vaguely triggered, although they cannot remember anything definite.