Upon starting high school, Futaba Ito welcomes her childhood friend Seiichirou "Sei" Izumi into her home since his parents are living overseas. Despite Sei's two-year seniority and charm, Futaba's older brother, Tsumugi, is hesitant about granting them unlimited freedom. Tsumugi cautions Sei against any inappropriate conduct, though their mutual attraction develops. As they exchange subtle smiles and clasp hands, Futaba begins to fall for Sei; nevertheless, his fervent devotion soon leaves her uncertain if she can cope with his intense feelings.
