Even after leaving Fujisawa for Ogaki, not one person remembered anything about Mai Sakurajima. Sakuta and Mai return to school together, but even there they hear from Sakuta's friend Rio Futaba that nobody at school outside of her has any recollection about Mai. At the same time, Sakuta hears of a theory that losing memories concerning Mai is based on a certain action taken, and struggles so that he doesn't lose his memories of her. And seeing Sakuta act as such, Mai makes a certain decision of her own as well...
Puberty Syndrome—a rumored, mysterious syndrome that only affects those in their puberty. For example, a bunny girl suddenly appeared in front of Sakuta Azusagawa. The bunny girl's real identity is Mai Sakurajima, a teenage celebrity who is currently an inactive high school senior. For some reason, her charming figure does not reflect in the eyes of others. In the course of revealing the mystery behind this phenomenon, Sakuta begins to explore his feelings towards Mai. Set in a city where the skies and seas shine, Sakuta unfolds the meaning behind his bizarre encounters on women with the said syndrome.
