Despite her gyaru looks, Aihara Yuzu is an innocent high school girl with no experience and no prior loves. When her mother remarries, she's transferred into the prestigious "Aihara Academy" for young ladies. However, on her first day at school she happens to witness the diligent student council president, Aihara Mei, making out with her hot homeroom teacher... Yuzu returns home, unable to hid how upset it left her, when her mother announces Mei will be her new step sister, and they'll be sharing a room...?!

Yuzu manages to reunite with her class, and then at the hotel she tries to confess her feelings and talk about that Christmas night with Mei. However, Mei tells her to forget about that night... Tachibana Nina happens to witness their exchange, and knowing about how her twin sister feels as well as her relationship with Yuzu, Nina resolves to help fulfill her sister's destiny. The next day Sara and Nina beat Yuzu's class to Yasaka Shrine, waiting for their chance.