Last night, I stood in the hallway, and I watched my 13 year old step daughter masturbate in her bedroom.

I had never seen a girl her age do anything like that. And I have to say, as dirty as it sounds, it was to me, sexually, one of the most amazingly stimulating things I have ever witnessed in my life.

She is probably about 5 foot 3, about 130 pounds, a bit of a stomach, and I'd guess based on her bras I've seen in the laundry, probably a 36 C. I had never seen her naked before. Until last night. She was lying on her bed as I walked by, her hands moving across her body, touching her breasts, caressing her nipples, and rubbing her blonde/brown pubic hair.

I stood there quietly in the hallway, and held my breath as I watched her use her fingers, and slowly enter her vagina, rubbing, caressing, touching, and I saw the glistening wetness between her legs. It was the first time I'd ever witnessed someone her age doing something like that.

It took about 20 minutes, but I watched her orgasm. Her body shook, she trembled, she gasped, she panted a little bit, and she fell back into her pillow, saying oh geez. Oh wow. Oh geez.

I stood there watching as she stood up off her bed, put on her panties and her little bra. She pulled up her shorts, and she put on her t-shirt, and she went downstairs. I had gone into my bedroom by that point, was rummaging around with some laundry and stuff, and pretended to not have heard what she'd done.

I know it's wrong. But seeing that petite cute little body, and seeing a girl her age for the first time ever naked, later that night, watching some porn, I fantasized I was fucking her, and having a massive body shaking orgasm inside a condom when I was inside her little body.

So wrong. But I can't help it that seeing something like that makes me fantasize the dirtiest most perverted sexual things I've never thought about.