As a 6 Year Old, Rintaro is diagnosed with Henisei Tashu Ijou Syndrome (also known as Hentai Syndrome), a disease that could kill him if he gets sexually aroused. To save him and provide a way for him to live as normal a life as possible, his father teaches him the ways to control his body and mind for ten years in the mountains, with the martial art of the Koei Sougetsu. When he's 16 he chooses to enroll Nangokuren High School, which he assumed to be the biggest all-boys school in the country but is actually the biggest all-girls school that has just gone coed.