After getting divorced, she raised her son on her own. She got a job and child rearing was over. When she thought about it, she felt a hole in Kokoro and lonely. Then one day, she went on a trip to a hot spring with her son... He suddenly confessed that he loved his mother. Even though they were mother and son... Mari refused at first, but she was lonely and could not bear her son's love, so she gave in and accepted him. This is the story of incest between a parent and child who get drowned in forbidden love and pleasure in the mountains of Gunma.