This all felt strange to me at first but after reading all the other stories here I've come to accept this as great experience and decided to share it.
My step dad is younger than my mom and is attractive with a nice body. I'm an only child and living in the same small house, I have seen his penis before, and he has seen me naked too. My mom works a lot and I know he gets lonely. I think I have heard him masturbating before in his bedroom while she was at work, I always wanted to go look but was scared of being caught so I never did it. Which leads to my story:
We live in a small house and I can see the bathroom from my bedroom. This particular morning the bathroom door was mostly open when he got out of the shower. I pretended to be asleep but watched him dry off. I usually masturbate in the morning so I'm horny anyway. I never really thought about him like this before but this really got me hot.
I rolled on to my back and brushed the covers off a bit and pushed my hand into my panties. I started rubbing my clit slowly. I had my eyes half cracked so I could still see him. I moved my hand enough to hopefully let him see what I was doing. He laid his towel on the toilet and started rubbing his cock slowly. I watched it grow and get hard. He is not big but he is not small either and has a very nice cock.
I'm soaking wet by now. I started to rub my stomach with my other hand and pulled my shirt up to play with my nipples and made sure he could see them. He started stroking his cock harder and I'm pretty sure he was looking at me. I could feel my orgasm building and started to move my hips a little. It was hard to keep quiet when I came. I looked at him and saw him cumming too, I kept rubbing my clit and kept it going.
I covered back up still trembling and watched him clean himself up. I smiled every time I saw him for the next few days. Neither of us have talked about this and appears to be our little secret. I don't intend to tell anyone either. I feel weird saying this but I can't wait for him to leave the door open again, I think about it a lot, I could never go any farther than this with my step father but I'm waiting for the next time I can wake up to another visual for my morning session. It was very hot!