There is a mysterious phenomenon going around that is affecting only certain teenagers at random called the "puberty syndrome". For example, Sakuta Azusagawa is your average teenage boy who just happens to see a bunny girl walk by him in the school library. The girl in the bunny suit is non other than Mai Sakurajima, Sakuta's upperclassman and also a famous actress who went into hiatus (for reasons unknown to the public) from the entertainment industry. For unknown reasons more and more people are unable to see Mai, and as the days progress the number of people continue to increase. Sakuta sets out to solve the mystery, and as he spends time with Mai, he begins to understand what a complex and wonderful person she really is. Other people who have "puberty syndrome" start to come to Sakuta for advice.