While looking for the cause of Mai's Adolescence Syndrome, Sakuta ends up scheduling a date with Mai. On the day they promised, Sakuta tries to help out a lost little girl on his way towards Fujisawa Station. But, he is misunderstood to be a perverted maniac by another girl, and because of that, he ends up arriving late to his appointed time to meet Mai. He somehow gains Mai's forgiveness and they proceed with their date, but Mai changes their destination, and takes Sakuta to Shichirigahama Beach...

Upon inducing a case of "Puberty Syndrome" where two copies of herself exists, Rio ends up staying at Sakuta's house for the time being. Meanwhile, "the other Rio" has been busy posting various unexpected photos on social media. After being informed about these activities by his classmate, Saki Kamisato, Sakuta decides to have a chat with "the other Rio." As he learns more about each of the Rio-s in hopes of discovering the reason for "the other Rio’s" actions and possibly a cure for her "Puberty Syndrome," Sakuta begins to realize the troubles each of them carries...