Yuzu Aihara, a fashion-conscious girl with no romantic experience, faces a drastic shift when her mother's remarriage lands her in a strict all-girls school that bans makeup and accessories. Sparking controversy on her first day by flouting the rules, she clashes with the school's disciplined student council president, Mei Aihara, her newly-discovered stepsister. Their contentious relationship takes an unexpected turn when Mei kisses Yuzu, leading to conflicted emotions that challenge Yuzu's perceptions and desires.