Ep. 9: Sister Panic
The new school term has begun, though Sakuta, who has been barred from going on public dates with Mai due to her agency's policies, is unable to find her. Upon spotting her on the street, he discovers she has swapped bodies with Nodoka Toyohama, an idol and Mai's younger half-sister. As the two try to adjust to their new lives, Sakuta learns the siblings harbor a grudge toward each other because of expectations levied on them by their respective parents, with Nodoka especially resentful of having to live in her older sister's shadow. During a video shoot, Nodoka collapses as what is typically a routine act for Mai proves to be too overwhelming for her. Mai later gives Sakuta the key to her house and orders him not to open a certain cabinet. At Mai's house, Sakuta comments on Nodoka's effort, and while she is bathing, he approaches the cabinet. (Source: Wikipedia)