Osawa works at a fitness gym that boasts 24-hour private rooms, and tries his best to keep his cool while dealing with the sexy students. But then Riko, a girl with a natural bust and a voluptuous body that's just his type, appears in front of him for a trial membership. Tired from staying up all night and faced with her perfect voluptuous body, Osawa's rationality flies out the window!? Riko is obedient, and even when she tells him dirty lies and touches that are supposed to be body checks, she believes everything is just instruction... The erotic sex exercises for Riko, who is trying to get her perfect body, are escalating more and more!?