Set at Hachimitsu Academy, a prestigious all-
girls boarding school with a notoriously strict, traditional atmosphere, the narrative shifts drastically when the institution finally admits male students for the first time. Only five boys enroll: Kiyoshi Fujino, Takehito "Gakuto" Morokuzu, Shingo Wakamoto, Joji "Joe" Nezu, and Reiji "Andrei" Ando. Heavily outnumbered by a thousand female students who initially view them with absolute disdain, the boys quickly realize their dream of a high school paradise is an impossible fantasy.Desperate for female contact, the boys hatch a clandestine scheme to sneak off campus to peek into the girls' communal bathhouse. However, their clumsy operation is discovered by the Underground
Student Council (UST), a ruthless, tyrannical trio consisting of the sadistic president Mari Kurihara, her towering, martial-arts-expert vice-president Meiko Shiraki, and the stoic, whip-wielding secretary Chiyo Kurihara—who happens to be Kiyoshi’s innocent crush.Captured red-handed, the boys are sentenced to a month-long imprisonment inside the academy’s makeshift detention block, known simply as the prison. Guarded by the relentless Meiko, who subjects them to brutal physical conditioning and psychological humiliation, the boys endure grueling daily hardships. Despite their harsh confinement, their motivations differ wildly; while Kiyoshi strives to maintain his integrity and keep his blossoming romance with Chiyo alive, Gakuto emerges as a fiercely loyal tactician willing to sacrifice his dignity for the group’s grand escape plans.The core conflict escalates when the malevolent official Student Council, led by the corrupt Chairman, conspires with the UST to orchestrate a mass expulsion of all five boys. The Chairman desires the boys' failure to discredit Mari and abolish the academy's co-ed experiment, while the UST secretly uses the expulsion threat as leverage. To save themselves, the boys must orchestrate an elaborate, high-stakes prison break.The climax centers on a coordinated breakout attempt designed to allow the boys to attend an outer-campus sumo wrestling tournament—their only alibi to prove they haven't violated the terms of their detention. Juggling near-impossible logistical hurdles, shifting loyalties, and severe punishments, Kiyoshi and Gakuto push their bodies and minds to the absolute limit. Through sheer tenacity, strategic brilliance, and bizarre camaraderie, they ultimately succeed in their breakout, exposing the corruption of the school administration and securing their freedom while forever altering the chaotic social hierarchy of Hachimitsu Academy.