In the library one day, Sakuta Azusagawa, a high school student, meets Mai Sakurajima, a woman wearing a bunny suit. It turns out that she attends the same school as him and is a well-known kid actor. Sakuta is the only person who can see and hear Mai, despite her notoriety and provocative appearance; for some reason, people haven't been able to perceive Mai for a few days, so Mai came to the library to check it out.
Sakuta thinks if the so-called "puberty syndrome," a mystery occurrence about which tales have been spreading on the Internet, could be connected to this. He makes the decision to investigate further and spends more time with Mai to solve this puzzle. In the process, he learns more about her and her emotions and meets other girls who also have "puberty syndrome."
