Sakuta had been waiting for a chance to spend time with Mai, but instead he's greeted by a stranger who looks just like her. Apparently, Adolescence Syndrome has forced her to swap bodies with Nodoka Toyohama, a flashy up-and-coming idol...who also happens to be Mai's sister from a different mother! Now, forced to pretend to be the other, the sisters go about their lives but it seems like Nodoka is preoccupied with something besides walking in Mai's shoes...