Tsukasa is a warden in Japan's most brutal prison, where serial killers and maniacs were held. He looked after them, kept notes, and watched those who were making progress and becoming a more normal person. He was a rookie, and the senior guards decided to make fun of Tsukasa a little and forced him to keep an eye on the most dangerous killers, among whom was Rui, the guy everyone was really afraid of, and no one knew what was on his mind. "I assume you're Rui, and from today on, I'm the new leader."