After agreeing to harbor an abandoned cat, Sakuta finds himself welcoming a look-alike to his old school crush into his home. This does not sit very well with Mai, who is trying her best to be with her boyfriend amidst a demanding work schedule. Meanwhile, something appears to be up with Futaba.

Sakuta had been unable to see Mai, who was not only busy with work but had an order from her agency forbidding her from going on dates. The second term finally begins, and Sakuta is eagerly looking forward to seeing Mai again at school. But upon seeing Mai in front of his house, she greets him with a shocking, "Who the heck are you?" Upon confirming what the circumstances are, it comes into light that Mai and her little sister Nodoka Toyohama have swapped bodies. Until this new Adolescence Syndrome is resolved, Mai will be living as Nodoka, and Nodoka will be living as Mai.