During a visit to the local library, Sakuta Azusagawa unexpectedly witnesses a bunny girl roaming the halls—only to be further surprised when that bunny girl turns out to be his celebrity upperclassman Mai Sakurajima. When Sakuta realizes that only he can see her, he jumps at the opportunity to help.

Mai's enigmatic problem reminds Sakuta of both his own struggles and those of his sister. Each of these are cases of "Adolescence Syndrome," a supernatural condition that warps the lives of teenagers in mysterious ways. As Mai's condition worsens, Sakuta searches for the reason behind her gradual disappearance from the public eye while she still has a chance of recovery.