Due to his wife's hospitalization, the mother-in-law comes from Sapporo to help with housework! At 51, she boasts a slender figure and stunning, voluptuous breasts that defy her age. With just the stepmother and son-in-law living together, he becomes increasingly captivated by her sensual charm. As their bond gradually deepens, hidden feelings begin to emerge between them. Keeping it a secret from their daughter, their relationship grows ever more intimate.