A year ago, when I was 13, I had just gotten home from school and was heading to my room that I shared with my 15-year-old sister. My parents were gone away for their anniversary. I could hear moaning coming from inside, and I wasn't stupid; I knew what was happening.
My sister was with her boyfriend. It wasn't the first time this had happened, but usually, whenever I knew what they were doing, I would go into the living room and wait for them to finish, but in school that day we had just watched a sex ed. video, and I was particularly curious.
I cracked the door open just enough to see. I was very interested; I had never seen a penis before, and I had never seen any other pussy than my own. After watching for a while, my sister moaned louder than I had ever heard her and I saw what looked like my sister peeing, and then I realized she wasn't on her bed, but she was on mine, so I stormed in the room and yelled, 'Don't pee on my bed! Go pee on your own!'
Now, I know my sister isn't the nicest person in the world, but when she got up and chased me around the house naked I got scared. I didn't see what happened to her boyfriend because she locked me in the closet.
Later that night, after she had unlocked the closet, she said she wanted to talk to me, so I followed her into the bathroom. She told me that since I was staring at her privates, she got to look at mine.
At first I was shocked at this, but then as she pulled down my skirt and stuck her hand in my panties, everything felt so sur-real. She pulled them down and and continued. It was so sudden that I let out a little yelp, but then she laid me down in the bathtub after taking off my clothes and hers. She turned on the icy cold shower, and I began to shiver.
After a few minutes, she laid down and pulled my head towards her... There's a lot more to the story and I'd like to tell you more, but it's not allowed here. I have to go now, 'cause I have a 'playdate' with my sister. :D