Yuzu Aihara is a girl who loves fashion and is always worried about her appearance. She likes to go out with her friends, but has never kissed or dated anyone before. But her life turns upside down when her mother remarries and Yuzu is transferred to a very strict all-girls school, where she can't wear makeup and earrings or even bring a cellphone. Deciding to rebel, she dresses how she likes on her first day, and because of that, she is called out in front of the entire school by the student council president: Mei Aihara, a girl who is the complete opposite of Yuzu.

To make her situation worse, when Yuzu gets home, she finds out that she has a new sister, and it turns out to be none other than Mei herself. Annoyed with the circumstances, the student council president kisses her, in an effort to prove a point. However, everything changes when Yuzu seems to like it and can't stop thinking about it.