After killing Kaito's family, he joins the mafia to take revenge and tries to destroy the mafia from within the mafia.

When 17-year-old Riyo returns home from school, someone knocks on his door. As he opens it, he sees a beautiful girl with long black hair standing in front of him. She only says, "I'm sorry. Please forgive what I'm about to do." Before Riyo can understand her words, the girl suddenly cuts of...