I am constantly horny and masturbate my cock at least 5 or 6 times a day. Recently I have taken to cumming in my sisters panties, I take clean ones and cum in the crotch then put them back at the bottom of the pile and a day or so later check out the laundry basket to find her soiled ones. She leaves huge stains in them and I often jerk off with them day dreaming about her juicy puss. We live in a bungalow and the other night I came home from my mates and went out in the garden. Her bedroom light was on and curiosity got the better of me so I sneaked a look in. Her roller blind was down but there was a gap at the bottom so I peeked a look and caught her changing, I saw her huge tits swinging free from her bra and dark hairy pussy which got me stiff so I sprang my cock free from my jeans and went for it while spying on my sis.
From then on it's been a bit of a fetish for me, a few times she has just turned her light out and a couple of times I was almost caught out when she opened her window. I have had a few successes though, one time I saw her rubbing her tits and checking them out in the mirror, feeling her nipples which got me squirting, one time she was sitting cross legged on her bed with her laptop and I think she was being horny with her b/f on msn or looking at porn because every so often she would slide her hand up the leg of her sleep shorts and give her puss a rub, another time she was lying on her bed in a vest and knickers reading and she was rubbing her slit through her pants, later that day I managed to get hold of them and wrap my cock in them while they were still warm and damp and I pumped huge wads into the crotch dreaming of my cum mixing with her warm puss.
Then a while ago I planted my razor handle in her room as I had read some girls use the vibrating ones to get off. I waited for about an hour when suddenly I watched her grab it from her dresser, under her duvet I could make out her legs spread apart and the regular pumping actions of her hand, I was so turned on I pulled my pulsing cock out and stroked away watching my sis writhing about masturbating and sliding my razor handle up her juicy fanny, then her legs went straight and stiff and I spurted jets of cum all over the wall outside her room, a minute later she brought my razor out from under the duvet and placed it back on her dresser. The other day she said how my razor had found its way in her room to which I replied she could keep it, she sort of smiled and I have had many a happy jacking session watching her with my buzzing razor sliding in and out of the special place between her legs.