Hisae is a quiet and reserved woman who depends on traditional men for her life. After losing her husband and becoming a widow, she begins living alone in a small household with her father-in-law and his son. One day, unable to forget her late husband, she starts masturbating in front of his portrait—only to be caught by her father-in-law. Enraged, he ties her up and subjects her to various tortures, including candle play and vibrator torment. Gradually beginning to see her as a woman, the father-in-law starts training her as a bound sex slave. With each step of this discipline, new emotions awaken, drawing their relationship into deeper, darker territory.