Yuzu Aihara transfers to a new all-girls school after her mother remarries. The change is inconvenient, but Yuzu is determined to fit in and make new friends, including her new step-sister Mei Aihara, the school's student council president. Their initial interactions are tense, with Mei being cold and Yuzu trying to provoke a reaction. When Mei kisses Yuzu unexpectedly, it leaves her questioning the nature of their relationship and Mei's motivations.