This took place almost a year ago.
When me and my step-sister were very young (me being seven or eight, and she was four or five) we used to play doctor and our favourite part was getting to touch each others private parts. As we got older, naturally we stopped this and never talked about it, although it was something I would occasionally think about.
Now almost a year ago, I was home alone one night and I was jerking off right before I went to sleep, which is something that I often do. My step sister came in and I didn't even notice. She came downstairs to my bedroom to tell me what she had done that night, and opened the door to me masturbating. I reacted almost immediately, repeatedly apologising. She said there was nothing to apologise about and that she was planning on going upstairs and doing the same thing before she went to sleep. I had no idea that she masturbated, so we got into a little conversation about it.
After a while, she brought up the little memory of us playing doctor as kids. What she said next almost made me fall off my bed. She said that if I was up for it, she'd play a game of doctor for old times sake. I thought for a second, was this really the right thing to do? But my hard on got the better of me and I said yes.
She said she would examine me first and told me to strip. In no more than a minute I was as naked as the day I was born. We playfully went through all the procedures my heartbeat, reflexes, and such. Then came the genital inspection. I was already hard as a rock, so as soon as Kate's hands touched my cock, I almost exploded. She began to stroke me quite fast. I was really enjoying it, but couldn't last any longer when she began to finger herself. I blew my load all over her shirt. I apologised, but before I could grab a paper towel, she was naked. She lay down on my bed, spread her legs wide and said 'I don't want any other inspection, get right to my pussy.' Following her orders, I began to run my fingers around the outside of her pussy, avoiding her clit at first, but slowly making my way there. After a few minutes, my fingers were covered in her juices and she was moaning so loudly I almost cummed again right there. A minute passed and she screamed and came.
We cleaned up and hugged each other goodnight. It was a little odd over the next few days, but we were fine by the same time next week. Since then, she has said that we may play doctor again some time soon. Hey, I'm down for another!