My husband had a stepchild. Her name was Yuta-kun, and at first she was an obedient and good girl. However, after they started living together, he started missing school a lot, started playing around with girls, and his behavior gradually got worse... One day, Yuta saw a photo of me masturbating. Maybe it's my fault that Yuta-kun has changed...? Just as I was thinking that, Yuta pushed me down while my girlfriend's husband was sleeping... and we started having a physical relationship.