First cross with my sister-in-law

Hello how are you? I'm going to tell you a story that happened to me a while ago with a girl I met at uni. My name is Gustavo, and at the time I was studying medicine and had met a girl on the course. After several months of dating, I went to her house for her father's birthday; when we arrived, her mom, a beautiful woman, made me wait where I could greet her dad. As the night wore on, we waited for my sister-in-law to arrive so we could eat cake; but it was already late and I appreciated her just about then. When I saw her, I was struck by her tits and booty; her booty was better than my girlfriend's, but her tits were something from another world, with a cleavage that left nothing to the imagination. They introduced me, we ate cake, and after that we didn't go to sleep. I slept in my girlfriend's room but on the couch, a gurney. At 2 am, I went up to her and we had sex, very good. At one point I wanted to leave to clean myself off, when I opened the bathroom door I ran into my sister-in-law sitting on the toilet, me with just my boxer shorts on, just like in the photo.Uncomfortable moment, since it was already possible to observe that I still had my cock up; my sister-in-law saw me and said Now I understand why my sister was groaning haha it's not for nothing I didn't know what to say, I just laughed and left the bathroom. The next day when we saw each other she gave me a smile and said...... Will continue