I lay propped on my elbows feeling the rays of the afternoon sun warm my lean young body. The Aegean Sea sparkled and added to the bright radiance of the pale sand. From my secluded vantage point on the tall dunes, I could see bodies filling the beach below.

As I took in the sight of so many scantily clad women, I could feel my small Speedos tightening almost painfully. I had begged my mum for the money to buy some trendy board shorts for this family holiday, but in her usual way, she had insisted that buying something fashionable was an unnecessary expense. Instead, she made me try on my unfashionable tight blue Speedos which just about fitted and told me they would last another summer. As I became turned on by what I could see on the beach, my waistband started to move outward. Looking downward, I could see my well-developed manhood come into view. The tightness of my tiny trunks actually enhanced the sensations and as I felt myself throbbing ever larger, I could feel the backs of my trunks creeping up my bum uncovering more of my buttocks.

Luckily for me, there was no one around, my parents having gone island exploring for the day and my sister avoiding me as usual. I thought back to the morning's unusual events. My sister and I could never seem to avoid squabbling. Although we loved each other and had our quality moments, even in our late teens, we always seemed to end up bickering, and for mostly childish reasons. We had very similar natures and the family resemblance was striking. Both of us were brown-haired, lithe in build and very sporty.

Both of us had been late developers and like me, my sister had only in recent years shown the final results of puberty. Girls usually develop younger than boys do, and so despite an age gap of nearly a year, we were at a very similar point.

For both of us, this was probably the first holiday in the sun where we felt we had adult bodies. Not that I would have admitted to her, but my sister had become quite an attractive young lady. For this holiday she had clearly been made to use a swimsuit that was too small for her. My Mum had always been tough to get new clothes out of. She believed in making things last and was frugal to the extreme. She did not care whether we were fashionable or keeping up with our friends. Normally this would mean we looked a bit daft in slightly out-of-date or too small clothes.

In fact, that morning when we all headed out to the hotel poolside to check it out and I first saw her in that tiny bikini, it had been a bit of a surprise and not a bad one. The sight of her blossomed body, barely covered, had transfixed me. Her full breasts were not very well covered by the small triangles that would have been more than adequate last summer. Now, although not overly large they seemed very pert and there were clear signs of her protruding nipples. Slightly flared hips now framed the tiny triangle of fabric disappearing between her thighs. The back of them could barely cover her shapely bum, half-exposing wonderfully pert cheeks. The bikini was so tiny, and pulled so low at the front, that I guessed she could not have much pubic hair, if any. Maybe it was a family thing as I certainly didn't seem to have a great deal of hair down there. My sister caught me staring and, in my reverie, it took a few moments before I realised, she was staring back at me.

In those few seconds, she became very self-conscious as if she could feel my eyes burning her much exposed skin. Her tight body tensed, and her nipples hardened. In an abrupt tone, she asked what I was staring at, I childishly told her she was unbelievably pale, although at that point I could see the skin on her face and chest becoming flushed. She told me I was fat, which was understandable, not because I was, but because that's what she always said when she couldn't think of a good reply. In fact, there was barely any fat on me and with the last few years of playing rugby, my body had gained some decent muscle. I smiled at her as if we could both recognise my victory in her response.

Instead, her eyes moved down my body and took in my low slung and bulging trunks. Suddenly I was the one feeling self-aware, her smirk disappeared, and her eyes lingered as if she was not seeing what she had expected. She seemed taken aback for a second and I saw her swallow hard as if she too had a reassessment to make. Certainly, the last time she would have seen me in these trunks, they were not so tightly packed, nor would they have been pulled quite so low at the front due to my package taking more of the material than it used to. Whilst I did not quite have a six-pack, I did have a flat hard stomach with a distinct pelvic vee disappearing into my trunks.

After a few lingering seconds, she tore her vision from my crotch and looked into my eyes. For a fleeting second, I thought I saw a look in her eyes, I had never seen before on my sister. It almost looked like hunger. Old habits die hard, however, and this turned into an evil smile as she said my baby trunks suited me, as they were so out of date. At this point, she achieved victory, because I swore at her, which my dad overheard. The result being I got sent to the hotel room that I was sharing with my sister to calm down for an hour.

When I got back to the room, despite the situation, I was feeling pretty chilled really. After all, it was the first day of the holiday and I had two weeks in the sun to look forward to. I wandered out onto the large balcony. Quite a few floors down, I could see the hotel pool and all the sunbathers around it very clearly. Anyone looking up would only have been able to see my head and shoulders. It was our very first morning at the hotel, and as I surveyed the unfamiliar scene of so many young ladies in barely any clothing, I inevitably started to feel quite turned on.

In fact, my unfashionable trunks now started to feel quite slinky and sexy. As I feasted my eyes on the nubile bodies below, I lightly ran a finger across my fabric encased penis, which twitched in response. The tightness of my small trunks increased. I could feel the edges at the back creeping up my arse as my rigid tool took up more and more space at the front. The waistband at the front was also creeping lower. A gap started to appear at the top and I could feel the cooler air starting to reach the partially exposed skin on my throbbing manhood. I slid my finger inside and lightly stroked across the top. I felt incredibly horny, to be standing outside in the fresh air, in just a pair of tiny trunks.

I looked around carefully and feeling confident no one could see, pushed my waistband down until my erect manhood sprang free. The novel feeling of exposing my naked body outdoors, with the light sea breeze like a caress along my throbbing penis was almost too much to bear. I slid my trunks right off and stood completely naked with my erection sticking straight out. I imagined myself not only outside in the open but in full view of those semi-naked sunbathers below me. I looked back down at them and focussed on a distant female form.

I started to stroke myself to ease the building tension of my desire. The stunning nubile girl I had chosen seemed to be the best of them on the poolside loungers and was so nearly naked, that I only had to squint, and she appeared to be exactly that. She was lying on her front and had rolled the waistband on her bikini bottoms so low that the top of her bum crack was showing. She had also hitched the bottom edges up her firm buttocks as high as she could to meet them. From my vantage point, it simply looked like there was a horizontal line midway across her naked bum. Her top half was undone at the back, with the halter neck bit untied and lying loosely across her towel.

As I fixated on her shapely upturned bum, I thrust myself into my hand. Every thrust I made was, in my imagination, a thrust into her as I took her from behind. God only knows what that would have felt like for real, I certainly didn't. As I started to close in on that point of climax, I felt my manhood becoming super sensitive, almost charged with electricity. Being so naked and exposed added to the thrill as I pistoned my rigid burning shaft in my hand. Suddenly it was all too much, and I started to ejaculate. Every shot coming out felt exquisite and I felt like the orgasm might never end. I don't think I had ever come so strongly before.

I looked at the balcony wall and floor amazed at how much I had produced. Then I looked back out to reassure myself that no one had actually seen me. As I did so I took another look at the gorgeous body that had so added to my arousal. I gasped in shock; the girl was now lying on her back so that I could clearly recognise my own sister.

My initial reaction was horror. What on earth had I been thinking? Just now I had been imagining sex with someone that was actually completely off-limits. Once my initial reaction subsided, I just couldn't get her body out of my mind. I looked back and took in the sight of her as she now lay on her back. Her pert breasts which I had never before seen exposed, pointed straight up at me now, and from the front, her bottoms were even more exciting to look at. They were pushed so low at the front; it almost looked like she was partway through removing them. I couldn't see any pubic hair, but the bare mound of her pubic bone was clearly exposed. I knew enough from my magazines, to know her clit must be just under the top edge of her bikini. If she had ever had hair, she must have shaven it.

As I looked at her my feelings were torn. On the one hand, she was my sister and thinking of her in sexual terms was taboo, and yet there she was, a sexual being, looking extremely hot. New ideas ran through my mind. Did she get turned on by exposing herself like that? Did she get turned on by shaving herself? Did she masturbate?

My favourite fantasy was always imagining girls I saw in real life and picturing them masturbating. Funnily enough, I had first discovered this preference when I found a sexual health advice column in one of my sister's teen magazines that said that it was normal and healthy for girls to play with themselves. It had gone on to detail the various ways girls could stimulate themselves as well as providing line drawings of the various parts of the lady’s pussy and techniques to use on them. At the time this new knowledge was like a bomb going off in my mind. I played with myself all the time, and I knew my mates did, but until that moment I had never thought that girls did it too.

I had felt a thrill knowing my sister had read that article, and by the look of the well-thumbed pages, she had looked at it a few times too. Since then when I looked at girls posing in dirty magazines, I had started imagining them touching themselves as well, adding my own mental images to those in the mags. I also liked to imagine all kinds of other females doing it, whether it was celebrities, girls at school or even just women I saw in the street. The thought that they might also masturbate was the best discovery of my young life and had become the biggest inspiration for my own solo sessions.

Strangely it had never actually occurred to me to think of my sister doing it. It was just an area that was off-limits and very taboo. Now though exciting thoughts entered my mind. Did she do it in her bed at night, just the other side of the wall from where I lay in mine? Had she ever done it in the bath, before I took my turn in the water? What did she think of when she was doing it?

The image of my sister lying on the lounger crept back into my mind, only now she slid her hand in her bikini and was rubbing herself. As the imaginary scenario developed, I saw her pushing the bikini lower on her hips so she could completely expose herself. Now she was feverishly rubbing herself and moaning. As I quickly cleaned up all traces of my sinful thoughts, I kept returning to this burning image. I had always lusted over the female form, especially in its most attractive versions, and now here I was being exposed to one of the horniest looking ones I had seen, and it was that of my little sister.

As I reflected on her highly attractive body, I was becoming aroused again. I was still naked and felt the need to explore her sexual side even more. As I scanned the room my eyes fell upon her still mostly packed but open suitcase. As you would expect all her plain tee-shirts and dresses lay on the top. I started to carefully lift items to see if I could locate where she had packed her underwear.

It had been a long time since I had seen any of hers, and at that time it hadn't been very interesting. I found something. Carefully I pulled out a pale skimpy low-rider thong. Looking at it I couldn't imagine there was enough fabric to cover anything. They were low cut, with frilly edges. The tiny piece of material at the front was truly minuscule, and what there was of it was almost completely transparent. I had never imagined that my sister had anything other than plain childlike undergarments.

From now on, whenever I saw her fully dressed, I would be seeing her in a new light. Whatever clothes she had on, I would be thinking of incredibly sexy undergarments barely covering her body beneath. My manhood was by now throbbing again. It stood out hard and red and demanded to touch the flimsy fabric. I placed it against the crotch of the knickers, right where they would have been tight against my sister's pussy. I felt the connection as I rubbed my intimate part right where hers had been. Barely had the thought crossed my mind and I was cumming again. Somehow, I managed to miss her knickers and the case and shot over the table at the side. I carefully replaced her knickers and cleaned up all signs of my activity. Time for a cold shower, I decided.

When I turned off the shower, I could hear noises in the room, so I knew my sister had returned. I quickly dried myself and put my trunks back on before unlocking the door and stepping out into the room. I double-checked the room; in case I had left any evidence of my earlier activities. The room was a large room with twin beds, although both beds were in fact the size of a small double bed. Our parents had been unable to book rooms close together and had to have their double room on a floor above and at the other end of the building. It seemed quite cool to us that we didn't have them breathing down our necks.

As I entered the room, I saw my sister walking out onto the balcony still in her tight little bikini, the bottoms had ridden most of the way up her shapely bum cheeks. She kicked off her flip flops and moved one of the loungers closer to the edge where it was fully in the sunlight. As she heaved it over, I got another chance to take a good look at her while she was distracted. She leant over, away from me, to spread her towel and straighten its edges. As she did so, she knelt on the edge of the lounger with her firm looking bum stuck in the air.

I assumed she wasn't aware of what an eyeful I was now getting. The vee of her bikini bottoms was pulled partly into her pussy leaving the soft pale skin at the sides exposed. I almost thought I could see a little bit of her labia and the dent where they were pulled into her pussy was very clear. I had a strong physical urge to step up and undo the ties on the sides. Her pneumatic body was a sight for sore eyes, and I found myself starting to get aroused again. It wasn't a big leap of imagination to see her naked from behind; with me lowering my trunks and grasping her hips as I entered her in that position.

I decided I better go somewhere else before it became too obvious. I headed for the door, grabbing my towel, and a few items. As I did so I called back to my sister to tell her I was going to the beach. She shouted something back, which I missed, forcing me to turn...