This role-play is performed by adults. Shinji tries to make up with his wife, who is sleeping after fighting over trivial things, by having sex with her. While massaging her plump butt, she cums all over. When I felt more comfortable with the tightness than usual and pressed for a kiss...it turned out to be my wife's sister who was there! "I-I'm sorry, sister-in-law!" Shinji apologized as he fell to the ground, but the sister-in-law forgave him, but she couldn't stop her body from starting to ache.