Hachimitsu Academy, one of the strictest girls' academies in Tokyo, has decided to admit boys into their system. Kiyoshi Fujino is one of these new boys, but he discovers to his shock that he and his four friends—Takehito "Gakuto" Morokuzu, Shingo Wakamoto, Jouji "Joe" Nezu, and Reiji "Andre" Andou—are the only male students among 1,000 girls. The draconian laws that are still in place make the school even worse, which punishes even the most minor infractions with a stay in the school's prison. The five boys all commit voyeurism in the school's bathing area with the lecherous philosophy of "all for one, one for all". Their capture and "arrest" by the Underground Student Council causes the five boys to receive an ultimatum: either stay a month in the school's Prison Block or be expelled. The boys are incarcerated in the Prison Block together and Kiyoshi is overwhelmed by the discovery that all the other boys are masochists that revel in the punishments handed to them by their attractive but vicious supervisors.