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The private all-girls school Hachimitsu Academy stands on the outskirts of Tokyo, a strict boarding school for sporting elite young women that upholds traditional rules on its campus. However, the new academic year sees the reform of one tradition: the admittance of male students. Though the few accepted boys including Kiyoshi Fujino are thrilled by this discovery, only five boys enter the cohort with a 1:200 boy-to-girl ratio on the first day of school. To their dismay, their adolescent dreams are crushed when they are unable to interact with the schoolgirls due to the written threats of the misandric Underground Student Council. The infiltration of the girls' bathing area by the five boys results in their internal imprisonment in the school's Prison Block, where they receive an ultimatum from the USC to stay a month in the prison or be expelled.