Yuzu, who looks just like a playful high school girl but has never experienced love, transfers to a city high school due to her parents' remarriage. On her first day at the new school, frustrated that she still doesn't have a boyfriend, she has a disastrous encounter with Mei, the beautiful student council president with black hair. After accidentally witnessing a kiss between Mei and their handsome homeroom teacher, Yuzu finds herself unable to erase the scene from her mind, despite her feelings. To make matters more complicated, she becomes a "sister" to the student council president and ends up living in the same room with her?! The two high school girls, who are complete opposites, are drawn to each other while also clashing. The love affair of the sisters begins!