Ijuuin Shou is the leader of the Grand Cross, a gang of delinquents with over a thousand members. Yamada Tatsuhito is a perennial errand boy with no presence in class who is the bottom of the school hierarchy. When Shou ends up hospitalized, he proposes that Tatsuhito take his place as his body double for a month while he recovers to prevent the gang falling into disarray. Tatsuhito, who goes from a life of being bullied to a life as a delinquent leader, struggles to get through each day without others finding out his true identity. Takahashi Fumiya takes on a dual role of both characters.

Genres