Setting up to get caught by my sister.
When I was about 16 I "accidentally" let my sister catch me.
I was laying on my bed on my back, stroking to a Penthouse, when I had a thought to have my sister catch me.(she was slender had a great chest and I had spied on her getting off several times).
I closed my door almost all the way but left a slight crack, just enough to see in but not so much that it was obvious. There was a chest of drawers just outside my room that held bath linen etc.. The perfect set-up. I could hear her walking down the hallway as I was stroking. Then I could hear one of the drawers slowly open, then close. Then the next slowly open, all the while I was stroking and getting even harder and hotter knowing she was watching. I gave a bit of a show. I would massage the head then play with the precum. Spreading my wetness around my cock then stroking some more. One hand, both hands, back hand and really getting into it. I began stroking faster bucking my hips into my hand then finally let loose, shooting cum all over my stomach and chest. I tried to give her a real show. I could tell it was then that she walked away as I heard her bedroom door close.
I'm pretty sure my show got her a bit horny as well. Not too long afterwards, I could hear her bed shaking and squeaking. Just hearing that had me getting hard all over again.
I have had her "catch" me a few times since then. Another time was as I was laying out by the pool. She was supposed to be at work but I heard her come home early. Story for another time.