The Haruna family lives happily with the wife, her husband, and her father-in-law. However, she is worried about not being able to have children, so she consults her father-in-law. The father-in-law is also unable to find an answer, but the wife thinks that her husband has many siblings and that her father-in-law's sperm is strong, so she asks him to inseminate her. At first, she thinks it's just a business, but gradually she becomes addicted to having sex with her father-in-law. They promised to end their relationship once they had a baby, and when she found out she was pregnant, their relationship came to an end. However, after the birth, they finally couldn't hold back and resumed their insemination sex...