Prison School (2015) - Season 1

There was a time when the Hachimitsu Private Academy was a revered and elite all-girls' boarding school on the outskirts of Tokyo but a recent policy revision is allowing boys into the student body. On his first day, Kiyoshi Fujino discovers that he's one of only five boys enrolled at the school. Completely overwhelmed by the thousands of girls on campus, the few boys find that their situation is less than ideal.