Moe Sato is a young lady who finds a cat and starts taking care of him. Named Poyo due to his round shape, he quickly becomes a dear member of the Sato family. (Source: ANN)

Hachimitsu Private Academy's five male students have been released from their oppressive prison captors, allowing them to return to their ideal school lives surrounded by short-skirted girls. With their freedom restored, things could not be going better for the gang. Kiyoshi Fujino and Shingo Wakamoto have formed close bonds with their female classmates; Reiji Andou is the center of attention due to his masochistic quirks; and even Takehito Gakuto Morokuzu—notorious for defecating himself during class—befriends the klutzy yet like-minded Mitsuko Yokoyama. However, in contrast to his fellow ex-convicts, Jouji Joe Nezu struggles to readjust to student life, and the unlikely romantic success of his friend Gakuto pushes him to his wit's end. Feeling ostracized, he begins to wonder if life was better behind bars.

Located on the outskirts of Tokyo, Hachimitsu Private Academy is a prestigious all-girls boarding school, famous for its high-quality education and disciplined students. However, this is all about to change due to the revision of the school's most iconic policy, as boys are now able to enroll as well. At the start of the first semester under this new decree, a mere five boys have been accepted, effectively splitting the student body into a ratio of two hundred girls to one boy. Kiyoshi, Gakuto, Shingo, Andre, and Jo are quickly cast away without having a chance to make any kind of a first impression. Unable to communicate with their fellow female students, the eager boys set their sights on a far more dangerous task: peeping into the girls' bath! It is only after their plan is thoroughly decimated by the infamous Underground Student Council that the motley crew find their freedom abruptly taken from them, as they are thrown into the school's prison with the sentence of an entire month as punishment. Thus begins the tale of the boys' harsh lives in Prison School, a righteous struggle that will ultimately test the bonds of friendship and perverted brotherhood.

Insecure Ai Shiomi begins attending the prestigous Psychic Academy for psychically gifted students, following in the footsteps of his legendary older brother. (Source: ANN)