One day, Shohei's father brought along a young and beautiful woman named Sanae. Eventually, Sanae and Shohei became mother and son, sharing their last name together. For Shohei, who lost his mother at an early age, he had never been accustomed to living with a woman in the house. It was also a shared life with Shohei and a beautiful woman whose age had not changed too much. It was a strong stimulation for Shohei. And that day would come. Shohei could not control his sexual desire and had intercourse with Sanae.