When he returns to his parents' house in Bon, Koji is confused because his brother and his wife seem to be rubbing for infertility treatment. That night, when he happened to take a peek at the couple's activities, he couldn't take his eyes off his sister-in-law, Riho's nasty idiot. Riho wants to get pregnant, but instead of keeping her peeping secret, she begs Koji, who has a girl, for a vaginal cum shot. Koji ejaculates unbearably in the back of Riho's vagina as she is swept away by the fierce invitation of her sister-in-law who hides in her family and secretly sweats and devours a meat stick.