Incest mother and child swapping

Yurika, who is being pressured to divorce by her estranged husband, makes a mistake with her son, Koichi, as her nerves begin to wear down. Koichi loses his energy after witnessing Yurika's hysterical screams every night, and one day he confides a secret to his friend Satoshi... However, in reality, Satoshi has been having a relationship with his mother, Sumika, that has crossed the line for several years. And Satoshi whispered to Koichi. ``Let's have fun swapping each other's mothers''...