While her husband has taken a mistress and stopped returning home, Reiko is determined to raise her son Ryota on her own. However, his absence leaves her emotionally lonely, and the weight of daily solitude bears down on her. Amid this struggle, Ryota notices his mother's loneliness and wants to comfort her, holding her close to ease her pain. In response to his heartfelt concern, Reiko opens herself to him. In turn, Ryota dedicates himself completely—pushing to his limits—to heal his mother's heart. Between the two, a forbidden bond begins to form.