Puberty syndrome – Abnormal experiences rumored on the internet to be caused by sensitivity and instability during adolescence. This year, Sakuta Azusagawa, a second-year student at a high school near Enoshima, meets several girls that are experiencing this “puberty syndrome.” For instance, he meets a wild bunny girl in the library. She turns out to be an actress on hiatus, Mai Sakurajima, who is also his senior at the school. For some reason, no one else can see this enchanting girl. How did she become invisible…? As Sakuta searches for answers to help Mai, they spend more time together, and he eventually learns of her hidden feelings… This is an unusual story that takes place in a town of bright skies and glistening seas, where Sakuta encounters various intriguing girls.

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...

With Sakuta's help, Kaede is able to go to school at night. She is now enthusiastic about heading to school during the day. However, on the following day, the original Kaede's memory suddenly returns, eradicating all memories of the Kaede that had spent the last two years together with Sakuta. A certain person appears before Sakuta, who is overwhelmed with grief because Kaede was no longer around.