Three years after getting married, my wife got pregnant. She said she was going to give birth at her parents' house and decided to go back home. I was thinking that living alone for the first time in a while might be okay, but my wife's younger sister came to help with the housework. When I met my sister-in-law for the first time in a while, she had grown breasts and looked mature and attractive, and although I knew it was wrong, I couldn't help but see her as a woman. I couldn't calm down thinking about the two of us being alone in the same house. Then, I saw my sister-in-law masturbating and couldn't help myself and approached her. Since then...