I have always fantasized about my wife's sister, and my wife and her know all about it. We often tease each other and make little comments here and there to see each other's reactions, but we all knew nothing would ever happen. At least that's what I thought! My sister-in-law was in town for a couple weeks and was staying with us. I came home from work a little early one day and saw that the vehicles were all gone and no one was home. I went up stairs to change and noticed something move in my son's room at the top of the steps. This is where Christy was staying and she was lying on the bed totally naked with the door open just enough to get a perfect view.
The bed was up against the wall on the opposite side of the room and I had a nice side view of her entire body. It was as nice as I had dreamt about. The movement I saw was her massaging her pert B-cup breasts and tweaking her nipples to make them erect. I was instantly hard as a rock, but I didn't know what to do. My mind was racing and screaming for me to RUN!, but my feet were not about to move. My eyes were glued to her body and her hands as they made their way down between her legs. Christy is about 5'9' tall and weighs about 125 lbs., muscular, with a perfectly flat stomach (the kind where her hip bones stick out when she is lying down). She has long, straight, bleached blond hair and I found out that day that her perfectly trimmed pussy is blond also. My wife's body is very similar to hers, but my wife has sandy brown hair and brown pussy hair. This difference made things even more exciting.
I was mesmerized as Christy was slowly masturbating without knowing I was there watching. She rubbed her clit in a slow circular motion. She seemed to get her self very worked up, very quickly. She built up the tempo until her right hand was rubbing her clit so fast that it was a blur. She was pulling on her nipples with her left had and starting to arch her back. I could tell it wasn't going to take much longer and that it was going to be a good one. When she started to cum she let out a low moan and arched even more. Only her feet and shoulders were touching the bed when the orgasm really hit. I couldn't believe my eyes. She was squirming and moaning and bucking all over. It was the hardest orgasm I have ever seen a woman have.
Just as everything had subsided and Christy was catching her breath, she rolled over and looked my right in the eyes. Next, the door flew open and there was my wife. I was busted. My wife said to me, 'Enjoy the show?' I couldn't answer, it was the most incredible thing I had ever seen, but I was in so much trouble. My wife grabbed a hold of me and jerked me into the room. I thought I was dead! She said that now it was the girls turn to enjoy a show and told me to strip down and masturbate for them. I turned bright red from embarrassment but was really turned on at the same time. My wife stripped down and sat on the bed right by her sister's face and started to play with her clit. The whole time all this was happening Christy was slowly rubbing her pussy again. I couldn't take it. I stripped down and started stroking my cock. I was standing there masturbating with my cock just inches from my sister-in-laws face with my wife stroking her clit right next to her.
It didn't take long from all the visual stimulation for me to orgasm. I shot my cum all over Christy's breasts and neck. My wife reached over and rubbed it all over her breasts and nipples. This added stimulation caused both of them to start cumming. It was unbelievable standing their watching both of them cum together. We all collapsed and lay there for a few minutes before anyone could say a word. I think we were all in shock at what we had just done. Christy finally broke the silence by suggesting that next time we get out the video camera. I hope that day comes someday. Until then, I can vividly recall the events of that day in my mind.