Yuuki Anzai, the half-devil who once pulled college student Tsukasa Taira out of a devil's attack, has left police work behind. By 2024 he heads a security section in Tokyo, still holding his own bloodlust in check under a strict no-human-blood rule, when he meets Leo Torasawa, an athlete who was set to represent the United States at the Tokyo Olympics. The two begin tracing a chain of forced double suicides that started in America back to a group that calls itself Justice.