Yuzu Aihara, a fashionable, spontaneous and fun-loving city-girl, transfers to a new neighborhood and high-school after the remarriage of her mother.

More preoccupied with boys and shopping than studying, Yuzu struggles to fit in at the conservative girls' school and frequently clashes with the student council—specifically Mei Aihara, the hard-working, beautiful but cold student council president. As it turns out, Mei happens to be Yuzu's new step-sister and Yuzu finds herself having to share a bedroom with a girl she absolutely can't stand.