The narrator recounts how his parents were murdered when he was young, leaving him an orphan. As a child living on the streets, he is attacked by bullies until an old man named Noboru rescues him. Noboru offers to take the narrator in and train him for 10 years so that he can get revenge on the person who killed his parents. The narrator, named Kazuo Aoaka, accepts Noboru's offer in the hopes of finding the killer and getting answers about why his parents were murdered.