Desperate to save her sick mother, Miku repeatedly pleads with her uncle for money to cover the medical expenses. However, her uncle deceives her, luring her into a hidden underground cell where he imprisons her. As she fiercely resists, he intimidates her, pressing, "Don't you want to save your mother?" Gradually, through intense bondage training, she undergoes repeated convulsive orgasms with eyes rolled back, transforming into a submissive slave.