Many regard the rare Puberty Syndrome as a mere myth due to its supernatural symptoms that only affect teenagers. However, Sakuta Azusagawa, a high school student, knows firsthand that it is a genuine and prevalent disease in his school. Mai Sakurajima, a once-famous child actress-turned-third-year student, is also a victim of the syndrome. She exudes an unapproachable aura that repels her peers, but Sakuta discovers her wandering in the library wearing a bunny girl costume. Despite her unusual attire, no one takes notice of her, prompting Sakuta to approach and help her. As he aids Mai with her syndrome, he encounters other girls struggling with the same enigmatic illness.