When I was 16 (two years ago) my sister Kate, who at the time was 14, and I had been at the pool, which wasn't far from our house, with some of our friends. We went back to our house to change into our regular clothes. We were planning to walk down and eat ice cream with some friends of ours, but Kate said she wasn't feeling good, so she stayed home.
I got halfway to the place that I was going to meet my friends and realized I had forgot something. I went back home and walked upstairs to where our rooms were. The area is carpeted and therefore is very hard to hear anyone walking there. When I walked by Kate's room, her door was partly open and she was standing against the wall, facing me, completely naked. I had always thought that she was quite beautiful, and already had a fairly curvy figure, long blonde hair and blue eyes. I was shocked at how good she looked standing there naked. Her breasts looked almost like a womans, and she had a considerable amount of blonde pubic hair and pretty legs.
She was leaning against the wall with her eyes closed and was thrusting her middle and ring fingers of her right hand rhythmically into her slit, slapping her palm against her pubic area with each thrust. She kept saying, 'it feels so good, it feels so good, ahhhh, feels so good, ahhh' over and over. I positioned myself where she couldn't see me if she opened her eyes (which she never did) and watched her.
She was obviously feeling a great deal of pleasure. As I watched her, my penis was so hard that I could feel an orgasm building without even touching myself, the head of my dick was straining against my underwear, and I could feel a few drops of an ejaculation well up and begin to ooze out, the orgasm sweetness going up almost all the way-I bit my lip to try and hold back the orgasm, since I didn't want to soak my pants.
She started thrusting her fingers harder-it looked like she was going all the way from her clit almost to her anus with her fingers, not inserting them, her palm slapping in rhythm against her blonde pubic hair. Her perfectly shaped breats started to look like they shrunk a little and the skin turned red on them-her nipples began to get rock hard, and as they did she reached up and began to wildly tug at one nipple with her other hand.
She started to throw her head back, thrust her fingers harder, and a few seconds later her legs stiffened up, she stood up on her tiptoes, she got an very painful look on her pretty face, and said, 'UHHHHHH, AHHHHH, HUHHHHHH! ARRRRRHH!' and she shook her head back and forth. At that point I had to walk away because if I had looked at her one more second, an orgasm would have begun in my pants, which I couldn't afford to happen right then.
When I got home that night, I masturbated to an extremely strong orgasm thinking about how beautiful and sexy that Kate looked as she was masturbating-I ejaculated an enormous amount of semen as I thought about her standing there fucking her pretty self. I thought of all that intense pleasure that she was feeling, especially when she went through that strong orgasm that she had. In some ways I felt guilty about feeling that way, but, I figured, it was something I had seen accidentally, and she was physically becoming a woman and having adult feelings, and it's just the way it was.
It was hard for me to look at her in the same way now. After that time, sometimes I would find myself getting horny when I was around her. She's developing and getting prettier, and sometimes when I'm near her I just want to walk up and kiss her and caress her beautiful breasts, but I just fight the feeling and keep going. She has no idea that I saw her that day.
I have had many orgasms thinking about the sexy sight of her masturbating, and right when I'm ready to ejaculate, I'll think of her screaming during her orgasm, and that brings me over the edge. I think about her laying in her bed giving herself orgasms (which I'm sure she does) and imagine what she looks and sounds like as she does it. She may be my sister, but I still think she's beautiful and sexy.