I, 35M at the time, used to live right next to my sister in law,26F at the time, for about a year and a half. Before that she lived a 25 miles or so away and rarely ever seen each other.

One evening she came over asking if I could change her furnace filter for her. No problem, I went over after I finished dinner and my wife went to take a bath.

She was well known for wearing very short, loose fitting shorts with nothing under them. So much so that her sister noticed and told her you could see everything between her legs when she would bend down at all.

Her furnace was in a very large closet that you had to go through her bedroom to get to. Walking through I noticed a vibrator half tucked under a pillow and made a funny comment about "this is how porn starts" and went into the closet to swap out the filter.

When I came out of the closet she was sitting in a chair in the living room giving me full view of her freshly shaved pussy since her shorts covered nothing the way she had plopped down in the chair.

I told her as much and walked over to act like I was going to touch it and she didn't flinch or move at all. Just looked up at me waiting.

I so I reached down and touched her pussy. Already so hot and wet, her little moan and lip biting as I started to rub it was all it took. I had my zipper down and I was in her as fast as I could. I tried pulling out but her legs locked me in and I cum so hard in her. Slowly, I realized what just happened and she assured me she was on birth control and not to worry about that. She also said she wouldn't tell her sister.

That was the first time.

Since then for a year and a half I'd go over there to fix this or look at that and fuck her every which way while her sister was at work or watching TV.

It's been a couple years since all that now and she found a steady boyfriend. We still flirt but the sex is gone and our secret is still just that. It was fun while it lasted. On to the next sister maybe. Haha