Manjo Taiga is the poster child of the underworld.
Ever since he can remember, he has been trained in the art of living in the underworld and is an expert at killing.
However, the overwhelming presence of yakuza in the underworld is a thing of the past.
The Yamada-gumi, to which Taiga belonged, has been dissolved and reborn as a katagi (organized crime) company.
The new job is that of a cleaner.
The killing genius is transformed into a cleaner. His workplace is a school, not the underworld.
Now that he has become a “katagi” (a professional corporation), killing, violence, and fighting are forbidden.
But what awaits Okawa is a delinquent high school with bullying, violence, smoking, drinking, and all kinds of problems that even the teachers and adults can’t handle.