In the far future of Assassin Sakurai, the twins went their separate ways; Takuto moving away, and Kazuki staying to care for their mother who fell ill after the death of Kurosaki, who was murdered by a mass criminal. Thirsty for revenge, Takuto follows in his father's steps and becomes an assassin aiding those lost in their life and killing those who cause trouble. On the other hand, Kazuki becomes a detective and is assigned to the case of the Reaper. Without being aware, Kazuki is chasing after his criminal brother who he vows to catch, no matter what.