I opened my eyes just a little, and I could definitely see her there, reflected in the mirror on my wardrobe. She was peering through the gap at the back of the door, her eye against the crack where she had a good view of me, but safe from being seen herself, or so she thought.
I'd crashed out on my bed after taking a shower and was chilling out. My workout at the gym had really pumped my muscles and after the high of lifting weights for a couple of hours had worn off I'd just relaxed back on the bed and drifted off in to a doze.
I was home for the summer after my first year away at college and took the chance to meet up with the old gang and work on my fitness. Having just turned twenty I was in good shape and carried a nice amount of muscle on my 6 foot frame, but I always liked to work on my definition. Suzanne, my sister had just turned 18 and was growing in to a real stunner. Not having seen her for a few months I was pleasantly surprised how her figure was developing. She played a lot of squash and had developed a slim figure, with long toned legs and the firm, rounded rear of an athlete. Her 34B breasts were pert and nicely outlined under her shirts as she gave up bras for the summer.
As I'd stretched back on the bed and relaxed I kicked the towel away and lay back naked, feeling the warmth of the sun streaming through the window on to my bare skin. Everyone else had gone out and I was on my own for a few hours so I hadn't worried about closing the door, thinking I had the place to myself. I hadn't realised Suzanne had forgotten her purse and had nipped back to pick it up. I was just laying back, eyes closed, and letting my mind wander. I was thinking about the girl I'd met at college just the month before and the date we had just before I came home. After a night of heavy drinking she had dragged me down an alleyway, pulled down my jeans and given me the most incredible blowjob. As I remembered the feel of her hot lips around my cock, her hand stroking my shaft, and her gurgle of pleasure as she tasted the pre-cum leaking from my swollen head, I could feel my cock start stir at the memory. With my eyes still closed I felt the heat as my cock began to stiffen, and the sensations of the growing hard on causing my glans to slowly slide across my stomach, my shaft becoming to a long hard line. I don't like to brag but I do have a great cock. Fully hard it's just over nine inches long, with a thick shaft that I can only just wrap my hand around, and a swollen smooth head that just begs to be sucked. From the first time I managed to get it in to a girls hand in 10th grade, word got around and I was never short of someone to get me hard and get me off. I lost my cherry to the gym teacher, Miss Heron, and never looked back.
As I got harder my hand reached down and I gently started to wank myself. Slowly at first, and then picking up the pace as the memories of pumping hot spunk down her throat became more vivid. I was just starting to contemplate shooting more spunk high in to the air when I heard a floorboard creak. I opened my eyes slightly, wondering if I had just been busted with my cock in hand and not wanting to face up to whoever it was. My head was turned away in to the room, but I could see the door in my mirror. There was no one in the open door, but I could see a shadow move at the crack along the rear of the door. We lived in an old house and the big hinges meant the door sat a good inch away from the frame when it was open. That one inch was enough for me to make out the dark fringe of Suzanne's black hair. Looking through the crack she could see me naked, stroking my raging hard cock, with my head turned away from her.
Thoughts flashed through my head about what to do, when I realised she had no idea I was watching her in the mirror. She thought she was hidden and I was totally unaware of her. I let out a gentle breath, realising there didn't have to be an embarrassing confrontation. Then I smiled slightly to myself as I realised my cock was still rock hard. Rather than shrivelling in shock at being caught by my little sister, I was finding the whole thing horny as hell. Keeping my eyes open just enough to watch her in the mirror, I took hold of my cock in just my thumb and forefinger, making a ring like a pair of lips. I stroked under the rim of my cock, teasing the sensitive underside, slow and firm, making sure Suzanne could see every twitch and movement of my raging hard on. I'd never felt so horny, and couldn't believe the thrill I was getting, knowing Suzanne was following every movement of my hand. I watched her shadow move as she pressed herself harder against the crack to get as good a look as possible. I could see her face and hair, the one eye I could see was wide and her lips were parted, her tongue wetting them as she watched me wank. Looking down I could just see her hand unbutton and then unzip her jeans. My balls were getting tight and I could feel my orgasm building as I realised what she was doing. Her hand slid down in to the top of her jeans and I watched see her wrist gently move from side to side.
This was unbelievable. Here I was lying naked on my bed, pretending to be alone while I wanked the hardest cock I had ever known, and my sister had her hand down her own trousers, peeping through my door and wanking along with me. I felt my balls tighten as I got closer. It took all my control to keep my head still and not let Suzanne know I was not just aware she was there, but having the best damned wank of my life because of her. Her wrist was becoming a blur, I could see her biting her lip, desperately trying to stay quiet as she got herself off watching her brothers enormous cock being pumped by his own hand. I heard a small gasp from behind the door and that was it, I shot cum high in to the air. My hips bucked and my fist grabbed my shaft hard as jet after jet of hot white spunk shot from the end of my cock. It landed on the bed, my stomach and chest, and even over the floor before the final steam ran down over my hand.
I let out a huge sigh as my orgasm began to fade, and I turned slowly on the bed, pretending that I'd just woken up from a great wet dream, not sure if I still had company. I heard the patter of feet heading down the stairs, and a moment later the slamming of the front door. I'm pretty sure Suzanne had a pretty good orgasm of her own, that was the gasp I heard that set me off, and it must have been torture to have to run off like that. I grabbed a towel to mop up the puddles of cum that were all over my room, and wondered what she would say when she got home later.