Thanks for the comments guys, I really appreciate it. The story gets pretty mature from here on in. You've been warned.

Enjoy.
The house was dark and smelled musty, as though it had spent a summer standing vacant. For a brief moment I regarded the room, lit by the ruddy orange glow of a streetlight. The floors were carpeted, and old-fashioned chairs and a couch were arranged about the room. I barely had time to take in these details before I was being pressed hard into the door by an incredibly beautiful woman. It was not unpleasant.
Sylvia took each of my hands in hers and gently but firmly pushed them above my head and against the wall. ?While I still can,? she said cryptically. She began to kiss me, softly at first, but with ever-building passion. Her movements became more frantic. Her lips pecked mine again and again, then she pressed into me open-mouthed for a long moment. Our tongues met, and I tasted her saliva mixed with the delicate flavor of vodka and triple sec. As far as I was concerned, it was the best thing I'd ever tasted. Gradually she migrated, finding my cheeks, my eyes, my neck. She nibbled briefly on my ear, and tugged on my earlobe with her teeth. The feeling of her warm lips against such a sensitive part of my body made my head swim, and I moaned loudly.
Somewhere in the middle of this she'd let go of my hands. I used this new-found freedom to touch her amazing body. My hands stroked her back, up to her neck. I ran my fingers through her long red hair. Opening my eyes, I found her looking right back at me. The stare she returned, the expression of adoration on her face, spoke volumes. This was more than a fling. This was something special.
I continued to her shoulders, running my palms across her arms, down to her hips. I felt compelled to touch every inch her, and I think she approved. The loosening fabric of her dress clearly indicated that, whatever had made her smaller, it was still happening.
My hands rubbed her sides, and inched up to trace the edges of her bosom. She responded by stepping back slightly, giving me free access to her chest. I spent a moment teasing her, letting my fingers draw circles around and between her boobs. Sylvia's eyes glazed over, and she clung to me tightly. When at last I could wait no longer, I gently took hold of her ample breasts. I fondled them, savoring their firmness, and squeezed them lovingly. She gasped in pleasure, and in that moment I actually felt her body dwindle in my arms. For some reason, this turned me on even more, and I redoubled my efforts.
Eventually she took my hand in hers and gave me a slight tug. ?Come on,? she said, her voice hungry, ?let's get more comfortable.? As she walked, I took the opportunity to gauge her size. The top of her head was now roughly level with my nose. My geometry isn't great, especially when another part of my body is sucking all the blood away from my brain. But I estimated that she was just a bit less than 5'6? tall now. That meant she'd lost nearly a foot in height since the evening began.
Her outfit, by some miracle of architecture, still clung to her frame. Its straps looked like they would desert her shoulders with the slightest provocation. Following along behind her now, I nudged one of them mischievously. Just as I'd hoped, any principles of physics that had been holding her dress up failed. Sylvia turned, a mixture of shock, humor, and lust on her lovely face, and I got my first glimpse of her unclothed. Her skin was creamy and flawless. Her body showed a surprising amount of tone, from a flat stomach with visible definition to subtle projections on her arms and thighs. Her breasts were huge and tear-dropped shaped, and in the instant that she'd spun to look at me they'd bounced in a way that was almost impossibly enticing. I was a bit disappointed to find a pair of silk panties, the same blue as her dress, still hanging to the generous curves of her hips. All in good time, I thought.
?No fair!? she pouted. ?If you're going to undress me....? And with that she began to slowly unbutton my shirt. It took awhile, because in between each button she paused to kiss the portion of my chest she'd exposed. I didn't mind waiting. Her lips felt so warm, so dainty against my flesh. As she worked her way lower however, an issue arouse. The sensual way she was kissing my stomach was really turning me on, and I began to wish I hadn't worn such tight jeans.
Sylvia noticed the uncomfortable bulge in my pants. ?What have we here,? she cooed. ?I wonder what I should do about this.? Her hand cupped my swollen manhood, and she massaged me gently. My moan was so loud that I startled myself, and I took hold of her shoulders for stability. She gave me one last pass with her palm, from tip to base, then abruptly stopped. The whole incident had lasted, at most, three seconds.
?Speaking of no fair,? I groaned. She stood, smirking. With a quick motion she unbuttoned my pants, mercifully relieving some of the pressure. Then she turned, and with her hips swaying majestically, sauntered to the couch.
I followed her quickly, the way a puppy follows its mother. Sylvia had lain down, spread-eagle, arms crossed behind her head. The view was easily one of the most inviting things I'd ever seen. I moved to join her, but she held up one hand to stop me, grinning. ?This is the no-pants couch. Only people who aren't wearing pants are allowed on the no-pants couch.? I laughed, and complied with her request.
I climbed on top of her, letting my body rest on hers. The feeling of our bare flesh pressed together, the soft pillows of her breasts beneath my chest, her lips once more against mine ? if this wasn't heaven, it was as close as I would ever get. We playfully wrestled, just enjoying being so close. Before long my erect member brushed against her womanhood and we thrust together, with only two thin pieces of cloth separating us. We pressed harder, building up steam. Our noises of pleasure mixed together, filling the room with the music of love.
Before long I noticed that my weight was getting a bit uncomfortable for my little lover. I sat up and, lifting her surprisingly light body, pulled her on to my lap. I kissed her again, with a slow, gentle precision, trying to convey the depths of my passion for my beautiful Sylvia. My hand caressed her inner thigh, drawing closer and closer to her sweet honey pot. At last my fingers came to the loose, silky folds of her panties. After a quick trace of anticipation, I stroked her firmly. She purred like a contented kitten, and wrapped her arms around my neck.
Before long her underwear were damp with her juices. With almost no effort I pulled them down and tossed them across the room. With her defenses gone, I began to finger her dripping little pussy in earnest. I teased her outer lips, then ventured inside, and thrust in time with her ragged breathing. She whimpered, and clutched me tighter. I pressed upward into her g-spot for a long moment, then pulled out to massage the hard nub of her clitoris. She bit her lip cutely, her eyes clenched shut. And again I became aware of Sylvia dwindling away. I could just barely feel her tightening around my finger, and if I looked close, I thought I could see her whole body getting smaller. I was beginning to formulate a theory.
Without a doubt, Sylvia was a few steps ahead of me here. Before long she rolled off my lap. The look on her face was diplomatic, almost pleading ? aren't I small enough already? She stood in front of me, and once more I was startled at her loss in height. It was difficult to judge from a sitting position, but she couldn't have been much more than five feet tall now. More evidence to support my hypothesis, I thought with a smile.
Sylvia knelt before me. With the slightest pressure she parted my legs, and began to rub my cock through my boxers. I groaned and leaned back, feeling all my muscles relax as she set to work. The lady was good, no question. The way she used her fingertips to tease me. The way she varied her speed. And she seemed to always know the best place to touch. Before long I was bucking my hips in time with her motion, lost in ecstasy. All the while she looked at me with a condescending smirk on her face. Somehow this made her all the sexier.
Before long she tugged at my underwear. Removing my undergarments was somewhat more difficult for her than removing hers had been for me. I lifted off the couch obligingly, and she slid them down my legs. Now that there was nothing between Sylvia and my rock-hard penis, she attacked me with everything she had. She stroked up and down my shaft while massaging my balls with her other hand. Periodically she'd rub the sensitive spot behind my head with her thumb, and whenever she did this my vision blurred.
She began to lick the sides of my cock, covering me with her hot saliva. By the time she finally took my length into her mouth, my reality was an incoherent mass of pleasure. Her tongue swirled crazily. She swallowed me deep into her throat, and pressed her lips tight against me. That was all I could bear. I came explosively, harder than I ever have in my life. I was scarcely aware that I was gripping her hair in my fists, or that I was howling at the top of my lungs. Sylvia, for her part, gulped down every drop, and managed to smile at me the whole time.
I laid on the couch, gasping for air and feeling my heart pound. The French call it la petite mort ? the little death. For once in my life I understood why. Sylvia crawled into my lap. Her body felt good against mine, soft and warm. She nuzzled my neck, and we cuddled together while I recovered. Meanwhile, I noticed that she was nearly the same height now as she had been when I stopped fingering her. My strength returning, I decided it was time for a test.