After losing her husband when her son Manabu was very young, a mother has raised him alone. As he approaches twenty and increasingly resembles his father, she feels both maternal pride and a woman's bittersweet longing. On the night of his twentieth birthday, they share his first drinks together. She drinks far more than usual, and the intoxicated adult son begins acting unusually affectionate toward her, drawing them into a forbidden night of sexual awakening and squirting.