Sakuta encounters a mini-skirt-clad Santa named Touko Kirishima, who reveals herself as the bearer of 'Adolescence Syndrome,' gifting it to his former middle school classmate, Ikumi Akagi. Ikumi, influenced by online prophecies, embarks on heroic acts. However, Sakuta witnesses her in action firsthand. As a mysterious poltergeist emerges, Sakuta finds himself entangled in a situation he inadvertently triggered. Unraveling these enigmas leads Sakuta to confront his own troubled history.