In the fourth installment of the Seishun Buta Yarou series, Sakuta anticipates reuniting with Mai, only to encounter a doppelganger. This mysterious look-alike turns out to be Nodoka Toyohama, an idol who has swapped bodies with Mai due to Adolescence Syndrome. As they navigate this bizarre situation, the sisters must masquerade as each other, all while Nodoka's hidden agenda threatens to disrupt the delicate balance.