Momo, a girl serving as a disciplinary committee member, visits the home of her reclusive classmate, Yūsei. However, the one who appears is a man named Hirai, a current Yakuza who has been close to Yūsei's father Kenta since the time when Kenta was also a Yakuza. Hirai uses the house as an office and for his shady dealings. Guided by Hirai, Kenta appears and tells Momo that it's better not to meet Yūsei because he is a useless person. However, Momo does not accept these words and ends up meeting Yūsei. As soon as Yūsei sees Momo, he overpowers her. Kenta and Hirai also join in, and...