Fucked my Sister-in-law

This year for Christmas, I (33M) rented a house up in the mountains for everyone to come stay at over the holidays. There was probably about 12 of us up there between all the families. Pretty much everyone is married or attached except for one of my wife’s sisters, she’s also much younger than everyone else (22), we’ll call her Amy.

We all have our own rooms, and ours is on the 2nd floor overlooking the patio/fire pit area. When we were getting ready for bed the first night, I started to get undressed and realized the shades were open. I went over to close them (just wearing my boxers), and as I was closing them I noticed Amy was out at the fire pit looking up at me. I froze, embarrassed, not sure what to do. I gave her a kind of awkward wave and she gave me a sultry smile back and grabbed her own tits. That really caught me off guard. I always thought she was kind of hot, and could feel my cock stiffening, I think she could see it too. I closed the shades before someone else saw anything.

The next day half of the group went into to town, and half of us stayed at the house. I stayed, and so did Amy. Once half the group left, those of us that stayed just kind of split up and did our own thing, I went to our bedroom to read. I was only about a minute in when the door opened and Amy walked in wearing a bathrobe. Before I could even say anything she opened up her robe and all she was wearing underneath was a small red thong and a red bra. It was crazy fucking hot, my wife never wears anything like that. She walked over to where I was sitting and started rubbing her hand on my pants, before I knew it my pants were off and my cock was in her mouth. It was just a blur and I was powerless.

She gave the sloppiest head, it was so dirty and felt so amazing. I told her I was about to cum and she stopped, stood up, turned around, pulled her panties to the side, and sat on my cock. She was so wet I could feel it running down me. I only lasted a couple thrusts before I told her again that I was going to cum. I thought she’d stand up but instead she just bounced up and down faster and said “give me all your cum baby”. I blew a huge load inside of her, and when she stood up my cum started to drip out of her pussy and run down her leg. She pulled her panties back over, turned around, gave me a kiss, then bent over and cleaned every last drop of cum off my cock with her mouth. Then she put her robe back on and left…I’m still just hoping she’s on birth control, especially because we have a few more nights here and I’m hoping to fuck her again.