First I would like to thank the voters, readers, and those who gave feedback and left comments. One person gave me a great idea for a future adventure that I can't wait to make happen/write about, and all gave encouragement, so thank you.
For those just signing on, the first part describes my wife's accidental exposure to a stranger, which left me with the realization that her exposure turns me on, and with an increasing desire to expose her again.
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Since the first encounter was an accident, and since I didn't know exactly how my wife felt about it, I started off small. Several times over the course of a few months I would get her aroused while we waited for a pizza delivery, making sure her bra was off and her nipples were hard, and then I would make her get the door when the bell rang. It wasn't quite as satisfying as when she answered the door in a wet white t-shirt, but I was still aroused by it, and it was a start. I think she started getting the idea, because she got in the habit of teasing me when she came back in.
"Look how much of me is showing through this shirt," she would say to me in a playful and shy manner, "my nipples are so hard, the guy couldn't take his eyes off my chest." She would hold her chest in front of my eyes so I would be able to see how tight her nipples pressed against the thin fabric. She would slide her hand up my thigh and feel how hard my sex was, and I think she knew why.
After doing this a few times, and having great sex afterward, I tried to egg her on to show more.
"I have an idea baby," I said as she kissed my neck, "why don't you wear that loose top you have next time, and lean over to show him everything."
She paused. You see, the top in question looks respectable at first, and is made of a fairly heavy fabric, but the neckline has loose folds of material that, when she leans over, just fall away and leave her exposed. I first noticed it when we played pool together. When she bent over to take a shot I would be able to see right down her shirt to her bra covered b-cups.
It took a little bit of convincing, and me promising not to beat the guy up, to get her into the idea of exposing her bare breasts to a stranger at our front door. But she agreed!
So, the next time we ordered food, I laid out that shirt for her to wear. She gave me a bit of a nervous look, pulled on the shirt, and bent over in front of the mirror to reveal every curve of her perky breasts hanging easily in view. "You look so hot baby," I said encouragingly, "you're going to make his day!" She smiled nervously as I told her what I wanted her to do: