Sayako lives with her husband and son. She and her husband are still on good terms and often sneak around when her son isn't looking. However, her husband's dick has gotten soft lately, and although it feels good, she isn't completely satisfied. Sayako secretly masturbates to release her frustrations. One day, her son finds her and says, "You're not satisfied with my soft dick, are you? I'll let you in." From that day on, she began to have sex with her son when her husband isn't looking...