An absolutely secret relationship. She has stolen her son-in-law's heart and body. She knows it's wrong, but she can't stop. Tsubaki is having a drink and listening to her son-in-law's complaints. Perhaps because of the alcohol, he embraces Tsubaki. Feeling lonely, Tsubaki gradually accepts him... One night, her son-in-law sneaks into Marika's bedroom. Knowing about the strained relationship between her daughter and son-in-law, Marika ends up accepting her son-in-law... Her son-in-law touches Natsuko's body, seeking forbidden pleasure. Natsuko knows it's wrong, but she thinks it will save her from feeling lonely... In the past, only missionary position was permitted for marital relations. Aya, who had only known that, was shocked by her daughter and son-in-law's sexual practices...