In the Kobayashi household, the wife, her husband, and her father-in-law lived together harmoniously. However, they struggled with the inability to have children. Noticing that her husband had many siblings, the wife suspected that her father-in-law had strong sperm, and decided to ask him to impregnate her. At first, their encounters were purely transactional, but she gradually became addicted to the sex with her father-in-law. Their affair ended when she became pregnant, but after giving birth, she could no longer resist and resumed having him inseminate her. A story of infidelity and desire unfolding within this trio's household.