There is a rumor about a mysterious phenomenon call "puberty syndrome." For example, Azusagawa Sakuta is a high school student who suddenly sees a bunny girl appear in front of him. The girl is actually a girl named Sakurajima Mai, who is Sakuta's upperclassman who is also a famous actress who has gone on hiatus from the entertainment industry. For some reason, the people around Mai can no longer see her. Sakuta sets out to solve this mystery, and has he spends time with Mai, he learns her secret feelings. Other heroines who have "puberty syndrome" start to appear in front of Sakuta.