I wanted to share a real life occasion where I got to fuck my sister in law and she never knew. I was out with a couple of mates and was asked to go along to a party both arranged at a local guys house. Anyway I arrived at the party and it was in full swing with most people either tipsy or pissed and there was the inevitable happening in a couple of the rooms upstairs. I had helped myself to a couple of drinks and been there about an hour when one of my mates called me upstairs and said "you have to see this, a bird is on the bed and taking a few cocks". I went with him and as I went into the room there was at least 4 guys in there and the girl in question was lying on the bed with her arms tied loosely to the head board and at the same time blind folded and a guy was on top shagging her. I had to look twice and realised that the woman was in fact the wifes sister who had recently split with her hubby. I looked at my mate and he also knew who it was and we both said nothing. Well the guys in the room were taking turns to stimulate her as she was blind folded and were pinching her nipples and rubbing her cunt when nobody was in fact fucking it. I decided to strip off and get a piece of this and whispered to one of the guys "are you sure she cant see anything" to which he replied "no she is totally blind". I moved forward and stood between her legs and pushed my cock towards her pussy until it was almost nudging her lips and then pushed all the way in. It felt absolutely fantastic and I began to pump my ass into her and she was moaning like a true slut and saying things like "fuck me hard" and "make me cum baby". I continued to fuck her really hard and was holding her legs up against me and then I shot my hot load into her and felt her tighten her cunt muscles on me as she let out a moan. "I don't know who that is but you can have me anytime" she giggled. I moved out of her and left room for the others to perform on her. Once my mate had been through her he joined me downstairs and we decided it would be better if we left. Every time I see my sister in law now I see her as the dirty slut who never knew that her brother in law has fucked her and shot his load into her used pussy. She will never know that I have seen her in a different light since that glorious party night.