This summer, my parents let me go to my brother's house in the city to play for a few days. The time here was right when my brother was on a business trip, so it was just me and my chubby sister-in-law at home. She has fair skin, big breasts and big toned buttocks. As soon as I met her, many evil thoughts arose in my mind. That night, while she was fast asleep, I sneaked in and had sex and got all the sperm inside her. Although I knew it was extremely wrong, standing in front of such a slim and provocative body, I couldn't help it. Until the next day, I continued to sneak into her room, but this time I was not as lucky as before, she found out about my wrongdoing, but instead of blaming her, she let me do the rest of the work.