I'd gone round to a mate's house to help him fix his car up. His parents had gone out after work and just him and his younger sister Amy were at home. She was lounging on the sofa watching TV, still in her school uniform. Her short blue skirt had ridden up and I could just make out her black and blue stripey knickers. I felt my cock thickening as I looked at her, she was engrossed in the TV and took no notice of me. Her long tanned legs were fantastic and I'd always admired her from afar.
My mate called out from the garage and I joined him at the car. I borrowed an old t-shirt from him and we spent an hour or so fixing the engine until we had it running smoothly. He said if I wanted to clean up I could take a shower and leave the t-shirt in the hamper, whilst he tidied the garage up. As I neared the bathroom I almost bumped into Amy as she came out. She had a short towelling robe on and had her dark hair slicked back from her shower. Her long slender legs were on show again, and I could see her breasts swelling out of the robe. My cock began a slow rise as she breezed past me and into her room. I grabbed a towel, locked myself in the bathroom and turned on the shower.
I stripped off, and went to put my mate's t-shirt in the hamper when I sam Amy's black and blue stripey knickers rolled up in her discarded uniform. I grabbed them and gave them a close look. They were still warm! I could feel her dampness in the knicker gusset and they smelt of young girl pussy. My cock was rock hard now as I licked and sniffed at her knickers. I began pumping my cock, any sounds drowned out by the shower running. I pictured Amy in her uniform, legs wide open in front of me as she rubbed her pussy through her knickers. She slowly undid her shirt and freed those young breasts and began pinching her nipples. I was dribbling pre-cum by now as I continued sniffing her knickers.
I noticed the knicker gusset had a double lining and opened the flap and stuffed my cock between the folds of the material. Oh wow, it was just like fucking a tight pussy! I pushed my cock in further and the tight feeling around my cock-end was great. I carried on pumping my cock inside the knickers as I imagined Amy near to orgasm. My own orgasm approached as I felt the tight material around my cock. Suddenly I was shooting my jizz inside Amy's knicker gusset, my hips thrusting in unison. I thought my cock would burst the material as I pumped my cream between the soft, slick cotton.
As my cock subsided, I flattened the material out, put her knickers back inside her clothing and left my t-shirt on top. I looked forward to coming round my mate's house in future!