It all started innocently, the way these things always do.
I was trying to get to sleep; difficult given that my parents insisted that, although I was 18, school nights meant bed by 11pm. It was made all the more difficult because I was still pretty pissed off because my sister had talked my parents into swapping our rooms. The old room I had shared with our elder brother was bigger but since he had got a place of his own I had had to take the smaller of the two, so she could have more space for clothes and the like. I had bitched like mad but to no avail and so I had shifted my gear and made the best of it.
My new room was an L shape and so to use all the space I had stuck the bed behind the door, a decision that I would soon find had a lot of advantages.
As I lay on my back staring at the ceiling a thin shaft of light suddenly lit up across my face. I looked at the clock, 11:30pm; it had to be my sister. She had been out with a friend drinking & by the sound of the crashing & mumbled curses the evening had been a success. Our house was quite old & the building had shifted over time so that even though my door was half closed there was a good three quarter inch gap running down the side.
Out of nowhere a thought popped into my head. My sister & I shared the only rooms on the top landing & our doors were adjacent to one another. Very slowly I pushed back the covers, turned over & slid my body forward. By keeping my head parallel with the headboard I should be able to see across the hall. My heart was beating like mad & the blood was pounding so loudly in my ears I thought my head would burst.
I looked down & realised that without thinking I had started rubbing my cock through my shorts. Like all 18-year-old boys I was no stranger to the pleasures of masturbation, to the point where my sister was convinced the extra time I spent in the bathroom must be some kind of obsession with washing. I had shot my load just a half hour earlier but the thought of catching a glimpse of something illicit soon had my hard-on back with a vengeance.
My eyes started to adjust to the light & I realised she hadn't pushed her door completely closed. At first all I could see was a section of wall & the long vanity mirror that my sister had put by the door, I could still hear her moving about and realised that she must be at the dressing table that was against the far wall. Suddenly her reflection appeared in the mirror.
Before she had started to take off her make-up she must have slipped out of her dress & hung it in the wardrobe, now here she was in just her underwear & boy this was no ordinary underwear. She was wearing a black, lacy, half cut bra which made her tits look much bigger than I had thought & matching high cut panties that seemed to make her legs go on & on. The stay ups she had on were the kind with the lace tops & the whole outfit looked like something straight out of the back of one of my magazines.
My sister is only a year older than I am but at that moment the difference seemed a lot more. I had never really taken much notice before, you know what siblings are like, when we weren't yelling at each other we weren't speaking. Here though was someone I had never met before.
My bossy grown-up sister, I had just realised, was gorgeous. She is about 5 feet 6 inches tall with long brown hair & a little button nose that makes her look cute. I knew that she had had a few boyfriends in the past but I had mainly ignored her & them, apart from the usual annoying things that a little brother has to do, and anyway, my Dad was quite strict about that sort of thing so she wasn't in to anything too serious.
My erection was starting to hurt so I quickly freed it from shorts & started to stroke it.
She was sitting on the edge of her bed & I could see by her movements that she was a little drunk. Slowly she sat back & lifted her leg in the air pointing her toes straight out. Very carefully she started to slide the stocking along her thigh & as more of that beautiful long leg came into view I started to wish that I were the one undressing her. She dropped the stocking by the side of the bed & repeated the same thing with the other leg. By this time my stroking had reached a steady rhythm & when I looked down I could see the shine of pre-cum glistening across my glans.
When I looked back I gasped, this was too good to be true, my sister was standing up again & was reaching behind her back. I started to stroke my cock faster while at the same time willing her to take off her bra. She brought her hands back to the front & leant forward letting the lacy underwear fall to the floor. I was in heaven. Her tits were magnificent, at least a 38D, with long pink nipples that seemed to stand a good half inch from the rose-coloured areola. I was pumping my fist for all it was worth now & I could feel my balls starting to tighten with the onset of my orgasm. She seemed to have a dreamy look on her face & I realised that she watching herself in the mirror. Her hands came back up to her breasts & she began to run her fingertips across them, circling the nipples, slowly arousing herself.
She leant her head back & closed her eyes & I could hear a soft moan escape through her just parted lips. When she finally reached her nipples she gently squeezed them between her thumb & index finger & the sensation caused her to arch her back, seeming to thrust her tits towards me. I had reached the point of no return & my cock swelled as I felt the familiar tingle of my orgasm building. I slowed my strokes, hoping to make the feeling last a bit longer but with the faint cries of my sister in the background I started to shoot string after string of white spunk across my sheets & onto the headboard. I slumped down on the bed my chest heaving like I'd just run a marathon. My eyes were closed & visions of my beautiful sister touching herself danced across my mind.
I looked back through the crack in the door but the light was off and the room was now completely dark. I quickly tried to clean up the mess but my spunk was everywhere, I couldn't remember ever having cum as much or with as much force. I crawled onto a dry part of the sheet & closed my eyes. Sleep came slowly; my head still whirling from what I had seen, my sisters hot body etched onto my retinas, my cock sticky with my semen.
+++++++
The next morning was a bit weird. My sister goes to college later than I have to be at school so I was up, showered and finishing my toast before she came down to the kitchen for breakfast. I said good morning but she just mumbled something about a hangover took some OJ and headed back to her room. As she left the kitchen I sneaked a peak at her ass as she passed by but she was wearing a long bed shirt that came down to her knees, the cotton hanging from her shoulders hiding the curves underneath. It was hard to believe that this shapeless, monosyllabic grouch was the sexy creature that I had seen the night before
I went to school but the whole day was a right off, I couldn't concentrate & seemed to have an almost constant erection. My mind was fixed on the coming evening & the chance to get another look at my hot sister.