A family consisting solely of a brother and sister living together for years. The younger brother harbors special feelings for his older sister. However, when she decides to get married and leave home, he finds himself unable to suppress his emotions despite wishing for her happiness, ultimately taking forbidden action. Meanwhile, the sister, aware of her brother's feelings, knows she can no longer belong to anyone else. The two are drawn together by fleeting, intense emotions, colliding in a single, life-changing moment. The events of that day profoundly alter their relationship forever.