While his wife is away in the hospital for childbirth, his wife's mother comes to Tokyo from Isesaki in Gunma Prefecture to help him with the household chores. He can't control his dirty and nasty feelings for his kind mother-in-law! Gradually, the mother-in-law and son-in-law become aware of each other as man and woman. They start to have an illicit relationship, which is a secret from the family!