At first I didn't know I was being watched. Then I did, and the fun really began.
This all happened when my wife's sister Meg was visiting us with her husband from out of town. Meg and my wife were sitting out at the dining room table chatting while in the very next room, door wide open, I watched TV while sitting on our bed. I was atop the covers, still dressed in my sleeping clothes, loose fitting drawstring shorts and a t-shirt, and I was idly stroking my semi-hard cock through my shorts while I watched the tube.
While I did this I could hear my wife and sister-in-law talking-hubby was out running an errand. They were no more than 10 feet away-but they were not in my direct line of sight. From my eyes, Meg was out of sight, and while she might have been able to see my bare feet at the end of the bed from where she was sitting, I was pretty sure she couldn't see what I was up to.
Then I spotted it. In my direct line of sight I could see Meg perfectly in the reflection of the big double glass doors leading out to the deck. The light was just perfect, because it was more like a mirror than see-through glass. I could make out every detail on her.
And what I saw was her looking directly at the door staring right at my busy right hand. Wow.
I did my best not to react, for fear that she'd stop watching, and I tried to keep her from noticing that I saw she was watching.
As she did, though, I moved my loose fitting shorts off to the side and completely pulled out my now rock hard cock. And I started to stroke. I was wondering how'd she react, and to my joy, she just kept right on watching.
And right on talking, too, though I could hear in her voice a breathy excitement that surely had nothing to do with the subject being discussed.
I kept as quiet as I could but continued to masturbate myself. At that point I could have come without touching it!
For her part, there was no pretense at all. She was openly staring at me going at it.
Suddenly, my legs stiffened and I shot a couple of strong shots up, landing back on my cock and hand. Man!
I stuck it back into my shorts, and waited a bit for it to subside to a deniable level before being seen. I grabbed a towel, threw it over my shoulder and stepped through the open doorway.
Meg's eyes went right for my crotch, which my wife couldn't see, thanks to the skillful placement of the towel. I was hard enough that I was still showing plainly through my shorts, and a big wet patch of cum showed right there.
'I'm going to go grab a shower,' I announced.
As I turned I caught Meg's eye and gave her a knowing look. It wasn't until that instant that she knew that I'd been aware the whole time.
This would lead to more interesting encounters down the line.