a hot day, but she seemed to be enjoying it a little too much, sliding the tip in a bit deeper than necessary. I wondered if she had ever... Suddenly I realized that I was staring, and she was looking at me questioningly with raised eyebrows.
"You've, um, got something there." I said, indicating the side of her mouth to cover my lapse in attention.
"Oh." She said, brushing the sweet droplet away, looking a bit embarrassed.
*
It seemed pretty pathetic to be stealing glances at my little sister's body every chance I got, but in my defense she had developed pretty spectacularly over the past year. I'd always known she was cute -- beautiful even -- in a little-sister kind of way. But there was no denying it anymore; with rosy lips, perky tits, and a curvaceous ass, she was a total knockout.
Compounding the problem was my lack of a girlfriend. Shyness runs in our family, and in many ways I had it worse than Libby. I wasn't hideous looking; I'd seen plenty of uglier guys with girlfriends. I wasn't broke either; in a year I'd be a college graduate with good job prospects. I wasn't even isolated; there were plenty of girls in my class. The trouble was that I got quiet around new girls I was attracted to. Some of them made an effort to get to know me, but I quickly entered the friend zone once they took my cool reserve for a lack of interest.
Porn kept me sane. That and my right hand. I slept late into the mornings when I didn't have work, and spent long nights jacking off to whatever pretty thing took my fancy. Of late I'd noticed a disturbing trend for me to search for slender brunettes with big hazel eyes. On some level I knew that my narrowing tastes reflected a need to vent the sexual frustration building towards my sister. But I shrugged off this warning as a passing phase, trusting that I'd soon be enjoying my regular varied pornographic diet again soon. Having Libby living in close proximity but forever off-limits would be enough to scramble any guy's circuits.
*
She went out that afternoon as she often did in the holidays. She had a tight group of girlfriends who liked to go shopping, to the movies, parties; the usual. Not that she was a wild party animal or anything, but that year all her friends were turning eighteen, so there had been more parties lately. Her own eighteenth earlier in the year had been a small but pleasant affair at a fancy restaurant in the city.
For my part, I spent the time facebooking intermittently and catching up on a novel I'd been meaning to read for ages, but hadn't got around to during the busy semester. On impulse I navigated to my sister's facebook page. With hindsight it's easy to see how far gone I was, how obsessed with her I'd become, but at the time it didn't seem that weird. Her profile picture showed her arm in arm with her best-friend-forever Chloe, both of them flushed with happiness.
My eyes wandered appreciatively over Chloe's fine features, fair skin, and lush red hair leading down to her gorgeous full tits encased in a tight tube top. I took the link to Chloe's page and began leisurely scrolling through her photo albums. She had been the subject of many a fantasy, I had to admit, as she had been frequently coming over to our house to hang out with my sis for years.
Before long, I came across a new set of photos she had uploaded recently and my eyes nearly popped out of my head. She and Libby had gone to the beach a couple of weeks back, and I could see that these photos belonged to that day. Chloe was radiant in her emerald-green bikini, which, whilst matching her eyes, was struggling to contain her breasts. The next frame stopped my heart; my sister looked good enough to kill. Walking side-on to the beach, her long, smooth chestnut hair shone in the summer sun, blown back by the breeze. Firm breasts stood to attention, perked up by the coolness of the recently-departed water. And stretched over her ass was a tiny black bikini bottom. I didn't even know she owned a bikini like that. Must've been Chloe's doing; bless her. Something snapped inside me. There and then I vowed to find that scrap of material.
Owing to my throbbing cock, I got up and walked a little uncomfortably into her room. As quickly as I could, without leaving behind obvious signs of my intrusion, I searched her wardrobe shelves. Finding nothing, and with no small amount of trepidation, I riffled through the clothes in her chest of drawers. Just when I was despairing at finding my ticket to a massive cum, I struck gold, right at the very bottom of the lowest drawer. Obviously, she didn't want mom stumbling upon this. The bikini bottom barely weighed more than a tissue, but that scrap of stretchy material held together by string-fine cords was heavy in my hands as I carried it back to my desk. I maximized the picture of my sister, ogling her long tanned legs running up to that fantastic ass. I moaned loudly in relief as I freed my cock from the prison of my boxers, sooo thankful that my parents were at work, and only half glad that my sister was out too. I briefly reflected that having her in the house while I did this would make it even hotter. Picking my stolen treasure up off the desk, I slowly dangled the fabric down until the crotch brushed my cockhead.
I let out the breath I'd been holding in anticipation. First contact. Fuck yes. I shut my eyes for a brief while, teasing myself by lifting them up and down along my shaft. A little precum leaked out, and I wiped it away carefully with a tissue, not wanting to have any incriminating evidence for her to find when she wore these next time. I had eyes only for my goddess of a sister and her heavenly ass. Transfixed, I wrapped her silky bikini around my cock and began to pump it. I knew this would be huge and, though I could feel myself teetering on the edge already, I held back, savouring the illicitness of getting off on my sister. This was the first time that I sinned against her in fantasy, and already I knew that I would never cum as hard with any other; she was my heroin. It was almost too much, the added thrill of rubbing something that had been in intimate contact with that ass, that pussy. She was sheer perfection, and I just knew that her pussy would be perfect too. She
must
be shaven or waxed: her bikini bottom would be too small otherwise.
While it was rubbing my cock into white-hot territory, on the screen that goddamn bikini was so frustrating visually. I desperately attempted to undress her with my eyes, visualizing stretching the thing over her ass cheeks and slipping it down her wax-smoothed legs. Suddenly I saw myself at the beach with her, guiding her to kneel down in the sand. I would bring my steel-hard weapon from behind, and punish her for wearing what really should be illegal. And she would love it.
I couldn't take it anymore. I saw one long ribbon of pleasure spurting up in front of me, higher than ever before, and then I slumped into my office chair, unable to do anything, but in no pain. The second shot came, and I struggled to keep conscious as the pleasure surged through me. Three. Four. Five. I was too high to recognize that I'd never shot so much in my life, and rode each wave with choked cries of "Libby, Libby, Libby!" before I passed out.
*
That was the first time anything like that had happened to me while masturbating, but then I'd never had wank-material that good before either. I came to after a few minutes, and somewhat groggily began to wipe the cum off myself until I glanced at her bikini, which had stayed wrapped around my now-softening erection. Libby's bikini. Guilt hit me like a thunderbolt. What had I done!?
You masturbated to your own sister, you sick fucker.
And so much for keeping it clean; the material was soiled beyond belief with my incest-tempted cum. White streaks gleamed brightly on the black fabric. I got a little panicked, and after changing into fresh clothes, I hurriedly carried it into the bathroom to wash out the damage.
I had just finished borrowing Libby's blow drier to complete the cover-up, and was walking toward her room with much self-congratulation at hiding the evidence, when I heard footsteps in the kitchen. Cursing, I realized that whoever it was must have come in unheard because of the blow drier. Quick as a flash I raced into her room, buried the swimsuit bottoms, and went out to meet whoever it was in the kitchen with carefully affected nonchalance.
