I had just gotten into jerking off, when the door to the sitting room opened, and in walked a woman.
I knew who she had to be, of course -- my brothers-in-law had brought home some friends from the pub a couple of hours before, and they had all played noisy drinking games. I'd retired to the sitting room, to work on the computer. After a while I had gotten into looking at some internet porn, and had gotten very turned on after reading an S&M story.
It had gotten very quiet upstairs, and I had figured they'd all passed out, or gone to sleep.
So, I felt safe, when I decided to have a wank.
The room's door doesn't lock, of course, but I hadn't been worried. My wife is always telling me I should lock the door to the bathroom, and I guess she was right.
I'd really gotten into the story I was reading--a bloke was tied up and nipple-clamped while his girlfriend slowly jerked him off, making him beg for it.
I decided to try and do as much of the story as I could, so I had put on some nipple clamps, after stripping completely naked, and then handcuffed my hands together. I had to leave them free in front of me to touch myself, and I had.
So there I was, naked, and slowly tugging my cock, when the girl walked in.
I gasped.
She looked startled too, and caught herself a minute, ducking back.
I started to flail about for the key, and she popped back in the door. She closed it behind her.
"Don't stop," she said.
I froze.
"Go on, do it," she said. "I want to watch."
"Do it," she said, "Or I'll yell."
It was late, and very quiet. I didn't want my anyone to come down and see me like this.
But would she really scream?
"Ahhh" she started.
"Okay!" I said.
"Put your hands on it," she said.
She moved closer and turned on a light.
She was now really close -- just a few feet away.
"Stand up," she said. I did.
"Turn around."
I turned around slowly, letting her look at me. I was turned on, but very nervous.
"Mmmmmm." she said.
She reached out and touched my ass. I gasped.
"Go on and do it some more," she said.