Since his son, Takumi, divorced when he was 5 years old, his father, who had raised him alone, remarried. - And living with her mother-in-law, Miki, begins ... - Miki, who is a caretaker, actively tries to shorten the distance between her and Takumi and even takes a mixed bath. Takumi, who was defeated by such a girlfriend, accepted it ... However, the stimulation of being washed is too stimulating for the virgin Takumi, and it explodes irresistibly. Miki gently wraps him who trembles with shame. And that led to a secret practice in the bathroom with my mother-in-law ...