Reika believed people could become a real family without sharing blood. After marrying a man more than a decade older, she quickly grew close to his adult son Tatsuya, who was near her own age, and they settled into an easy relationship much like siblings. Their peaceful life changes during a week alone together when Tatsuya approaches her not as his mother but as a woman. Reika initially rejects him in confusion, yet gradually finds herself unable to keep pushing him away.