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Introduction:

A girl steals an experimental breast-growth serum from her fathers lab, having no idea that it would turn her into a cock-craving, lactating bimbo slut as a side effect!

I bit my lip, staring at myself naked in the bathroom mirror. It was so unfair. I'd seen pictures; Mom had already had a beautiful pair of C-cups when she'd been my age. And by the time she'd had me, just a couple of years later, they'd swollen up to the most amazing double-Ds! But here I was, a week and a half since my eighteenth birthday, and I still barely even needed a training bra! I sighed, reaching up and giving myself a dejected squeeze. Maybe it wouldn't be so frustrating, if I didn't look just like her in every other way; I was tall, five-eight and skinny, with long, naturally blonde hair and bright blue eyes, and a cute little button of a nose. I actually really liked the way I looked... all except for my much too small breasts. I glanced down at the counter, to the vial I'd stolen from Dad's lab. Finally, that was about to change.

I'd been working for him weekends and summers all through high school, mostly just feeding the monkeys and cleaning their cages, doing all the grunt work Dad felt too guilty to make even his grad students do. I didn't mind. It was better than working in fast food, and it would be good experience for when I eventually started my own medical career. He'd been working on a breast growth serum—basically a boob-job in a bottle, a way to stimulate the body's own tissue to replicate and grow. And it worked perfectly! The human trials hadn't started yet, but Zhi Peng, Dad's lead post-doc, said it was just a matter of paperwork and time. They'd already started producing the vials for it, storing them until they got approved. It would be months before they realized that one in the back of the freezer had been swapped out with a blank. Dad was going to hit the roof when he found out... but by then it would be too late. And I was desperate... I needed this!

I took a deep, steadying breath, and picked up my phone. Approved or not, I knew I had to document what I was about to do, so I'd be able to track the changes as they occurred. I took two quick photos of myself in the mirror, one straight ahead, one in profile. I'd read the entire experimental protocol several times over, forward and back, and I set about cleaning the curve of my ass with an alcohol swab. I picked up one of the disposable diabetic syringes I'd bought from the pharmacy, inserting the needle through the cap of the vial and carefully drawing point-one-three millilitres, the exact amount the protocol calculated for my body mass. I held the syringe up to the light, tapping and checking for bubbles, expressing just the tiniest drop from the tip to make absolutely sure. Then, the moment of truth. I'd watched Dad's staff doing this a thousand times, but I was still nervous. At least I knew I wasn't going to fight or try to bite, the way the monkeys always did! I took a deep breath and clenched my teeth, twisting so I could watch in the mirror, wincing as the needle pierced my skin. I slowly pressed the plunger, then withdrew. I quickly covered the injection site with a band-aid, but it wasn't bleeding much. It was more to prevent getting blood on my panties than out of any real need.

I tossed the spent needle into the empty water bottle I'd chosen to use as my sharps container, then hid everything under the sink. Dad never used this bathroom, so I knew I was safe. I took one last look at myself in the mirror, wondering how long it would be before I started noticing a change, then quickly got myself dressed again and headed back out to meet him in the kitchen. He nearly had supper ready by that point, so I quickly set the table, and we ate chatting about our day as we normally did.

“Have anything in particular you want to watch tonight?” I asked as we were loading the dish washer. It was Friday, so that meant Daddy-daughter movie night, a tradition we'd been religiously keeping up ever since we'd lost Mom when I'd been little.

“Your turn to pick, sweetie,” he smiled warmly, pulling me into a one-armed hug and kissing me in my hair. “Why don't you go get started looking, and I'll be in in a minute.”

“'Kay!” I agreed, returning his kiss with one on his cheek, and went to go find something to watch. We tried to vary our genres from week to week, and Dad was partial to older stuff, especially black and whites. I'd learned to like them too; the old hard-boiled detective stories were my favourites, though some of the old war films were really great, too. Today though, I felt like something a little bit softer; I knew Dad was going to groan when he saw it, but I cued up a girly chick-flick and waited for him to arrive.

Sure enough, he groaned and rolled his eyes, but he didn't otherwise complain. He just wrapped his arm around my back, snuggling me close and kissing my hair again as I pulled our couch-blanket over our laps. I nuzzled against the side of his chest, breathing deep. He smelled so good today! I don't know that I'd ever really noticed that before... and the way he held me made me feel so loved, and safe! I started the movie with the remote, but already I was barely paying attention. I just wanted to snuggle even closer, to have him wrap me in his big, strong arms, and never let me go!

I was getting hotter and hotter under the blanket. I didn't think anything of it, not at first. It just made me feel so warm, and comfy... it was only when I caught myself unconsciously rubbing my thighs together that I really clued in, and noticed that I was wet! I tried not to think about it... but have you ever tried that experiment, where someone tells you not to imagine a pink elephant, and suddenly that's the only thing you can think of? It had to be the serum. Nothing like this had ever been noticed in the monkeys, but what else could it be? And it just kept getting more and more pronounced. Soon, it was all I could do not to moan. I swear, I was so aroused I could literally feel my own pulse throbbing through my pussy lips!

If that was all it had been, I think I would have been okay. I could have just waited until the movie was over, then gone back to my room to get myself off, the same as I always did before bed. But then the tingling started; it built up slowly, just like the heat between my thighs, but soon it was like thousands of little ants were crawling around inside my bra! I squirmed in my seat, trying to resist, but I just couldn't stop myself—I grabbed myself and squeezed, crossing my wrists and using both hands at once, desperate for relief. My eyelids fluttered closed, and I couldn't stop an involuntary little squeak of pleasure and surprise; my breasts were suddenly so much more sensitive than they'd ever been before!

“Madi!” Dad gasped in surprise.

“I...” I twisted to look up into his eyes, fumbling for words that wouldn't come. I was so ashamed, to be caught fondling myself right in front of him like that... but still I couldn't make myself stop! He stared at me in shock, but only for a moment.

“Oh my God... Madi, what did you do?” He demanded, his eyes widening as he realized the only possible explanation.

“I...” I whimpered and bit my lip, still mercilessly mauling my needy little titties as he watched. “I just wanted them to be bigger, Daddy...”

“I can't believe you would do something so reckless!” he snapped, the sudden anger in his eyes making me cower. “Do you have any idea how dangerous this was? Human trials have an approval process for a reason! And to not even tell me? Doing in secret, without anyone to monitor you? What if you had a bad reaction? You could have gone into anaphylaxis! You could have stroked out! You could have died, Madi! And I wouldn't have been there to help, because you didn't tell me what you were going to do!”

“I'm sorry, Daddy! I'm sorry!” I mewled. It wasn't fear for myself, but the fact that I knew I'd disappointed him that had the tears cascading down my cheeks.

“Oh, sweetheart...” he sighed, slowly shaking his head as he withdrew his arm from around my back. “I still can't believe you did this... but now that you did, you'd better let me take a look.”

I nodded through my sniffles, knowing he was right. I had to do whatever Daddy said, I wouldn't make that mistake again! I lifted myself up and spun on my knee, dropping myself into his lap straddling his hips, ridding myself of my shirt. He gasped in surprise, his hands finding my hips as my bralette quickly followed.

“Squeeze them Daddy, please!” I moaned, grabbing his hands and yanking them up to my breasts, holding them tight against me.

“Baby, I...” he shook his head.

“Please, Daddy!” I begged. “Please! It feels like they're burning up! Squeezing helps!”

“Like this, sweetie?” he asked, applying just the barest of pressure.

“More, Daddy!” I whimpered. “Your hands are so big, and strong! You can squeeze harder than me! Please, Daddy, I need it! I need your help!”

He gradually tightened his grip, and the more he did the better it felt. There may not have been a whole lot for him to grab hold of, but it still felt amazing even so! Only sometimes he would let go, which I hated... but he said he was testing something. I didn't understand what he said, but he seemed reassured that whatever it was, it was okay. I let my eyes flutter closed, losing myself in the moment, in the way his hands felt on my breasts! I started rocking my hips, reaching down between us...

“Madi!” he gasped, grabbing my wrist and pulling me away.

“Please, Daddy!” I mewled. “I need it! You don't understand!”

“I'm your father, sweetie! This has to be just the drug speaking, an unexpected side effect. You know we can't!” he withdrew his hands, shaking his head as he held them up in a sign to stop. That was my chance; I threw myself forward, plastering my lips to his, wrapping my arms behind his neck and holding on tight.

“Baby, no!” he tried to say, but speaking meant opening his lips, and I interrupted him by thrusting my tongue deeply into his mouth, swirling against his. But then he grabbed me hard by my shoulders, and he was too strong for me to resist as he pushed me away.

“Please, Daddy!” I reached for his cock again—he only had two hands, and they couldn't be everywhere at once. “You're already hard, see? You want it the same as I do!”

“That thing doesn't get a vote!” he growled as he yanked my hand away again, his voice so sexy, and deep! It made my insides clench, just hearing him speaking that way.

I whimpered, but clearly it was time to try a different tack. I jumped to my feet, undoing my jeans and shucking them and my panties straight down to my ankles. I stepped out of them and widened my stance, reaching down to spread my shaved, pink little lips right at Daddy's face. “Don't you see how wet I am? You have no idea how this feels! I need it, Daddy! I need your cock in my pussy!”

“Baby, no, we can't... you're just going to have to go to your room and masturbate, if you need it so bad...”

“I thought you wanted to keep an eye on me?” I grinned, licking my lips as I climbed eagerly back into his lap. His hands found my hips again, keeping me somewhat at bay, but not stopping me completely. It felt so hard to think, for some reason... but I knew I had him now! “I can't do it in my room, alone. What if something bad happens to me, like you said? I have to do it while you watch me, to make sure I'm okay!”

“I...” he began, but he cut off when I kissed him again.

“Play with my titties, Daddy!” I begged into his lips, backing away again before he could make me, running my fingers through his hair and staring deeply into his beautiful blue eyes, the same ones he'd shared with me. “Squeeze them nice and hard, while I play with my pussy for you!”

I reached down and started to do exactly that, rocking my hips in his lap as I rubbed my fingertips in tiny little circles over my hard, cute little clitty. He was hesitant, grasping my hips like they were an anchor of safety. But he kept looking me up and down, subconsciously licking his lips. And once I started fingering myself, my incredible wetness making me audibly squelch, he could no longer resist; he squeezed me even harder than before, making me tremble and moan as he kneaded my overly-sensitive flesh, my eyes fluttering closed in pleasure.

It was perfect... or almost so. As perfect as could be, while he was still stubbornly refusing me his cock. The heat was rising between my thighs, my orgasm slowly drawing closer... But then he gasped in obvious surprise, making me open my eyes. I quizzically tilted my head, but he didn't reply, his mouth gaping open in shock... he just squeezed my breast again, a thin stream of fluid squirting out to hit him in the chest! I gasped too, my eyes widening... This wasn't supposed to happen, none of the monkeys had ever reacted like this... but I instantly knew what I wanted, now that it had.

“Suck them, Daddy!” I begged, lifting myself higher onto my knees and pressing myself at his mouth. “Suck my milky little titties while I make myself cum for you!”

I could hardly believe what was happening... but for once, he didn't even resist! He dropped his hand from that side, grabbing me by my pert little butt and pulling me tight against him, sealing his lips around my tiny little pencil-eraser nipple and sucking for all he was worth! It felt so strange, feeling that hot fluid shooting out of me into his mouth... but I was loving every moment of it, especially the look of absolute rapture on his face as he eagerly swallowed it down! He swapped sides, and that one seemed to take some extra sucking to get it started for some reason, but soon he was able to go back and forth however he liked, milking me from both!

“Yes Daddy, yes! I'm going to cum for you! I'm so close!” I squealed.

“Do it, baby!” he gasped, backing away enough that he could look me straight in my eyes. “Cum for Daddy! Be my good little girl!” He took my titties back into his hands, giving me his hardest squeeze yet, and it was more than I could take.

“Daddyyy!” I screamed, thrashing as I vigorously, almost violently frigged myself into orgasm. It was so much stronger than my normal ones—it was only the strength of his grip on my boobs that kept me from bucking my way straight out of his lap and down onto the floor! It seemed to last almost forever, robbing me of breath nearly to the point of making me pass out. I did finally, slowly come down from it, gasping and panting for air. I slowly took my fingers out, and even that tiny bit of movement was enough to make me shake and moan with an unexpectedly intense aftershock. My fingers were covered with creamy white cum, more than I think I'd ever produced before... but as I brought them to my lips to clean them off, Daddy grabbed my wrist before I could. He slipped my fingers into his own mouth, instead!

“Fuck me, Daddy! Please!” I moaned, sitting back down into his lap and reaching for his crotch again. He was so big, so hard! I needed him inside me so much!

“You don't mean that, baby,” he sighed and shook his head, but he left my hand where it was this time, releasing his grip on my titties and encircling me in his arms instead, pulling me tight against his chest and running his fingers through my hair. “That's just the serum talking. This is precisely why the approval for human trials is so stringent—we had no idea it would be psychoactive in humans like this!”

“I don't know what that means,” I nuzzled into the crook of his neck, shaking my head. “It's so hard to think right now... but I don't care, Daddy! I just need you inside me! Please, Daddy! I need it so bad! Please, give me your cock Daddy! Let me make you cum!”

“God... you are not making this easy, baby!” he chuckled wryly, slowly sliding his hands up and down my naked, sweat-slickened back. “But I can't. Even if you weren't my daughter... you're worse than drunk right now, sweetie. Whatever you're feeling right now, in the moment... I owe it to future-you not to take advantage. You aren't going to feel this way once this wears off. If I do what you're asking... you would hate me for it, baby, once you come to your senses.”

“Never, Daddy! Never! I promise!” I whimpered against his neck. “I could never, ever hate you! I love you so much! I want to be with you, to give myself to you! Completely! And I need this, Daddy, please! You don't understand! I... I know it's doing something to my head. I can feel it. It's like everything is all fuzzy, and warm... but that doesn't matter, Daddy! I need your help! My fingers weren't enough. Whatever this is, whatever is happening to me... the one thing I know for sure is that I need your cock in me! I need it, Daddy, please! It's driving me crazy, not having it inside me! I need it! I need to get fucked! Please, do it to me, Daddy! I love you, I trust you... and I need it! Please, don't make me rely on some other boy! Somebody who really would take advantage. Please, Daddy... I'm going to get it, one way or another. I won't be able to stop myself! The way I'm feeling right now... you'd have to tie me down to my bed, to stop me! And even then, there's no guarantee I won't find a way to chew through the ropes! Please, Daddy... do it to me yourself! It's going to happen... and I want it to be you, not some other boy! Please, Daddy... take my virginity!”

He took me by my shoulders and pushed me back, peering searchingly into my eyes. I don't know what he was looking for... but he softly sighed.

“Forgive me, baby,” he stroked his fingers through my hair, and pulled me into a deep and passionate kiss!

I was so blown away, I barely even noticed as he stood, his hands dropping down to my ass to support me as he carried me through the house, my legs instinctively wrapping around his waist. Up the stairs and into his bedroom we went, where he laid me down in his bed. I sat up right away and tried to help with the buttons on his shirt, but I don't think I was doing very good—he laughed at me, taking my hands in his and kissing my knuckles, then wrapping them around the back of his neck and distracting me with another kiss as he quickly disrobed.

“Oh my God, Daddy!” I gasped as I got my first true look at him springing heavily into the air. He had to be nine full inches, and thicker around than my wrist! “It's even bigger than I thought!”

“Having second thoughts, sweetie?” he gave me a teasing smile. I giggled and shook my head, reaching down. He was so hot and heavy in my hands, his skin surprisingly soft to my touch, but with an amazing, steel-hard core within! I kissed him again, forcing my tongue deeply inside his mouth, then quickly laid myself back down in the center of his bed, licking my lips and invitingly opening my thighs. I expected him to climb right up on top—that's what I would have done, if our positions had been reversed! But instead he chuckled again at my eagerness, laying himself down between my legs, and started to lick!

I moaned and squirmed on the bed, torn between letting myself close my eyes, and attentively watching what he was doing! I'd never had anyone do this to me before... I'd never even had a proper kiss with a boy, before tonight! It felt incredible! So, so much better than just using my fingers! I ran those same fingers deeply into his thick, dark hair, pulling him tighter against my lips. I felt like I should be directing him somehow, telling him what to do, and where to go... but honestly, he obviously knew what he was doing far better than I did, so in the end I just laid myself back and let him do whatever he wished! He was constantly varying his technique, gently probing inside, swirling around my clitty, softly nibbling on my trim little inner lips. Everything he tried felt amazing! And not only that, but he slipped his hands in under my butt, squeezing hard, holding me tight against his mouth! Best of all though, was that look in his eyes. That incredible, predatory gleam staring straight up into my own as he ravenously devoured my juicy little pussy... my tight, creamy virgin cunt! I felt myself blushing—it made me feel so naughty just thinking that word, not even saying it out loud. But that's what it was, now... it's was Daddy's cunt, his to do with however he liked!

He was moaning happily, obviously enjoying himself—it made me feel so proud, that he clearly liked my taste! And oh my God, he was good! Already he had the pressure building up inside me again, a deep, wet heat suffusing my insides. I tried to hold back, tried to delay, knowing it would make it even better when it broke... but it was just too much! I squealed and kicked, my hands clamping down in his hair, my hips instinctively pumping against his face, coating him in my cream! He just tightened his grip on my butt, holding on for all he was worth, refusing to let me escape. Not that I wanted to, not really—but what he was making me feel was just so intense, my body couldn't help but try! Throughout it all that amazing, perfect tongue of his just kept lathering my sensitive little pleasure button, forcing me to unimagined heights, drawing it out beyond anything I'd ever felt!

He backed off a little as I started to come down, never fully stopping, but slowing enough that I was able to regain some breath. I giggled, biting my lip, stroking his hair. Surely now he would finally be ready to fuck me... but he just grinned at me, and dove right back in!

I whimpered, I cried, I begged... all to no avail. He moved his hands to the top of my thighs, establishing an even tighter grip, clamping me against his shoulders. And that was how he held me, pinned and helpless, forcing me through not one, not two, but three more orgasms in a row, each one longer and more intense than the last! And every time I came, it made little dribbles of milk leak out of my titties, covering me in a warm, slippery sheen. By the end, I was little more than a sweaty, cummy, mewling puddle of need in his bed, barely even able to twitch as he slathered my clitty with his tongue. Only then did he climb up on top of me, staring down into my desperate, panic-stricken eyes—as much as I wanted this, needed this... in that moment, I wasn't sure how much more I could take! But it was too late, I'd tempted him too much; he lodged his hot, swollen head between my sensitive, cum- and saliva-lubricated little lips, and gently began to push!

I gasped, my back arching up off the bed, my mouth gaping open and closed like a fish out of water, unable even to find the breath to scream. It hurt so much, but in the most incredible way! He was stretching me, my tender little bits burning like they'd been set on fire as that huge, rock-solid invader slowly forced its way inside... but somehow the pain of it only added to my pleasure. He was finally putting it inside, I was taking my Daddy's cock! My own father was fucking me, committing incest in my tiny, virgin pussy, and I was loving every moment of it! I grabbed his ass, trying to pull him deeper—he fought me, laughing and kissing me on my lips, not going one single whit faster than he intended. That was probably for the best... but I just needed it so bad! I needed to feel him all the way inside, needed to feel him thrusting hard, and deep, using my body for his pleasure!

He did start to thrust, but only a little, ever so gently easing me open for him and working his way deeper. I moaned into his lips, trembling beneath him as I felt that huge, hot cock exploring parts of me my delicate little fingers had never been able to reach. The world narrowed around me until there was nothing else left; only me, Daddy, and that amazing, gently thrusting cock! Time meant nothing anymore—I had no concept of how long it had taken him, but I could hardly believe it when I felt him pressing against my lips, rocking his hips to grind himself against my clit. Oh my God! I'd actually done it! I was taking all nine inches, all the way inside! The realization instantly had me cumming again, squealing my pleasure and pride up into the night, reflexively clawing at his back, my tight, wet walls clenching so hard it was almost painful, gripping around his cock!

“That's it, baby!” he purred into my ear. “Cum for Daddy! Cum on Daddy's cock!”

He held himself nearly immobile until I'd finished, just grinding himself against me to carry me through. But he was far from finished; the moment I was able to properly breathe again he started right back up, gradually increasing his speed and force. I forgot to keep track. I should have, I know—it was my first time ever having sex, I should remember every little detail! But it was just so incredible having him inside of me, the orgasms coming so fast, nearly overlapping each other! I know it was at least half a dozen... but honestly, by the time he was finally ready to join me with one of his own, it easily could have been twice that many! A change in his breathing was my first clue, and even in my orgasm-induced stupor, I recognized what it meant as I looked up into his eyes. I barely had the strength, but I wrapped him in my arms and legs, crossing my ankles and holding on tight, desperate not to let him get away.

“Give it to me, Daddy!” I wailed. “Please, cum in me! I need it!” I was terrified that he would withdraw, that he would deny me this one last thing.

“Oh, God...” he groaned, his eyes wincing closed, his body trembling above me with the effort of delay. But then it was happening. “Take it, baby! Take Daddy's cum!” he grunted, his hips taking on a life of their own as he pounded me hard, his huge, amazing cock pulsing inside me as he delivered his hot, incestuous seed!

“Daddyyy!” I screamed, the molten wet heat of his release tumbling me headlong into one last orgasm of my own, at least twice the strength of any he'd given me so far. Daddy was cumming in me! Filling me up, flooding my unprotected, fertile teenage womb with his cum! Claiming me, breeding me, making me his and only his, forever! I squealed and shook, gasped and writhed, every pulse of his cock inside me sending brand new waves of the purest pleasure racing down my nerves. I started to cry; huge, wracking sobs of fulfillment and joy. Daddy shook as he finally finished, rolling us so he was on his back, pinning me tightly to his chest under his arms.

“I love you, Daddy! I love you so, so much!” I blubbered into his neck, the enormous, swirling emotions of it all simply more than I could take.

“I love you too, baby!” he cuddled and kissed, stroking his hands up and down my back and ass. “So much! I love you more than anything! You have to know!”

I nodded that I did. I wanted to say more, wanted to explain everything I was feeling, even if I didn't have the words to understand it all myself. But as he snuggled me so tight, making me feel so warm, and loved, and safe... I was so exhausted after everything Daddy had just done to me, I was sound asleep and dreaming before he'd even softened enough to fall out!

***

I awoke slowly the next morning, a soft beam of sunlight from the window making it's way up my thigh, warming me through the sheet. I stretched and yawned, taking in my situation. I was still in Daddy's bed, but he must have moved me after I'd passed out last night; I was laying on my side, Daddy snuggled tightly up against me from behind, his arm wrapped around me and possessively cupping my breast. I squirmed again, guiltily biting my lip; he was hard with morning-wood, the huge, hot weight of him laying temptingly along the cleft of my ass.

“Morning, sweetie,” he murmured, softly, sleepily kissing the back of my neck.

“Morning, Daddy,” I giggled, continuing to squirm, making my intentions plain.

“None of that!” he chuckled, giving me one last kiss, then withdrawing his hand and backing away under the sheet. I twisted quickly around to face him, the dread hammering in my chest. Did he think last night was a mistake? Was he never going to let me do it again? He must have seen it in my eyes, because he smiled softly, reaching up to reassuringly stroke his fingers through my hair.

“How are you feeling, baby?” A seemingly innocuous question, but I understood what he meant.

“I'm back to normal, I'm pretty sure,” I blushed, glancing down from his eyes. “I... I don't feel like I did last night. The fog on my brain... I feel like I'm able to think clearly, again.”

“Are you sure?” he asked. I opened my mouth, but caught myself before I could give an automatic response. This was important enough I needed to make one hundred percent sure, for both our sakes.

“Pi is the ratio of a circle's circumference to its diameter, and is an irrational number equal to approximately three-point-one-four-one-five-nine. The speed of light in a vacuum, commonly denoted as 'c', is approximately two-point-nine-nine-seven-nine times ten to the eighth meters per second. Avogadro's number, which is approximately six-point-oh-two times ten to the twenty-third, is defined as the number of atoms in exactly twelve grams of pure carbon-twelve, also known as one mol. Should I keep going?” I smiled. “I'm pretty sure I can recite the periodic table down to Calcium or so... but no promises, once I get to the transition metals.”

“I think that's probably sufficient,” he chuckled, then grew serious again. “And... how much do you remember, about last night?”

“I remember everything, Daddy...” I bit my lip, my blush growing brighter as I struggled to find the words I needed to say. My mind may have been back to normal again, but that didn't make this any easier. In the end, I gave up—I decided to trust actions, instead, reaching across under the sheet, grabbing hold of his cock.

“Madi!” he gasped, grabbing my wrist. But I tightened my grip on him, and he was unwilling to pull me away.

“Last night...” I took a deep breath, steadying myself. “Last night was about what I needed, Daddy. And thank you... I realize now how difficult that must have been for you, given the state I was in, with me not really being able to consent. But this morning...” I looked straight into his eyes again, praying that he would understand. “This morning isn't about what the drug makes me need... it's about what I want, Daddy! All on my own!”

“Are you sure, baby?” he asked. I couldn't read his expression very well, but with my hand on his cock it meant I was able to cheat; he was twitching so hard, there was no room for doubt—he wanted this every bit as badly as I did!

I didn't speak. I just smiled, leaned forward, and kissed him on his lips. He resisted for all of about two seconds... then he was yanking me deeper into his arms, shoving his tongue into my mouth!

“If you don't mind, Daddy...” I giggled against his lips. “Do you think we could start with you sucking my titties for me again? My brain may be back to normal... but from how hot and full they're feeling right now, I think the milk production might just be permanent.”

“Gladly, baby!” he laughed, scooting down the bed a little and taking my nipple straight into his mouth. Sure enough I immediately started squirting, even more than last night since I'd just spent a solid eight hours filling them up for him while I slept.

“You really like that, hunh Daddy?” I purred in pleasure, softly running my fingers through his hair as he sucked.

“I love it, baby!” he grinned up at me, lasciviously licking a drop of my milk from his lips. “I always used to love doing this with your mom, too. You always got first dibs, of course... but you were a fussy eater when you were a baby, and your mom always produced way more than you could manage on your own, which left her feeling full and sore. I was always more than happy to help empty out the rest.”

“Well, we'll just have to see...” I giggled playfully, smiling at the details I'd never heard before. He hardly ever spoke about Mom—it was just too hard, for both of us—but I could just picture the three of us together in my mind; that story had been really sweet. “As long as your drug actually does what it's supposed to, and doesn't just give me the side effects, hopefully mine'll get as big as hers were, and soon I'll be able to give you more than just a snack!”

“You can't be serious!” he gasped, forgetting my nipple for a moment as he stared up at me in shock. “After last night... you can't really expect me to let you do that to yourself again!”

“Why not?” I giggled at him again. “I mean... I get why you were so conflicted, while my brain was being so wobbly like that, and you couldn't be sure it was what I really wanted. But that obviously won't be an issue, going forward. And honestly... it actually felt really nice.”

“It did? How so?” he asked, inquisitively tilting his head. It made me grin; even with his own daughter's swollen, lactating nipple between his lips, his scientist brain was obviously struggling to reassert control.

“It was like...” I paused, thinking of how best to describe it. “It was like everything else in the universe just kind of faded away into the background. Everything was still there... it just wasn't important anymore, is all. There was no work, or school, or anything else like that... it was just you and me, having sex. Looking back on it, with my mind fully functional again, I totally get that it was turning me into a brainless little bimbo slut... which sounds horrible, I know! But actually experiencing it, from my side of things... honestly, it was just about the best thing ever! Having my entire mind and body completely and totally focused on nothing but pleasing you... I'm not quite sure how else to explain it, but I definitely want to do it again!”

“Really?” he asked skeptically, but from the wicked little grin he was failing to fight off his lips, I knew he was already sold.

“Well, not right now, of course!” I laughed, shoving playfully at his shoulder. “I need to learn what sex is like without pharmacological assistance, first! But it is the weekend... so if I dose myself up again after we're done, it means you'll be able to stay here in bed, taking care of me the way I'm going to need until it wears off again!”

He laughed too, stretching upwards for a soft kiss on the lips, before eagerly returning to my breasts. I could hardly wait for them to start getting bigger... he seemed to like sucking on them so much, and it felt so good when he did, I really hoped I'd soon be able to give him more than my tiny little boobs could presently provide! I rolled him onto his back after he'd sucked me dry, pushing the sheet down to our ankles and straddling his hips—I really, really wanted to see what it was like being on top this time! I lined myself up and lifted him into place, but he grabbed my ass and held me still, stopping me before I could take it inside.

“Just be careful, sweetie,” he cautioned with a smile. “Just because you aren't a virgin anymore, doesn't mean it isn't going to hurt, especially if you try going too fast. Take whatever time you need... we're in no sort of a rush.”

“Speak for yourself!” I smirked, but I nodded to acknowledge his point, and he loosened his grip. And he was right, it did hurt—but not nearly as bad as it had the night before. Unfortunately, it wasn't nearly as easy to get into that pain-is-pleasure headspace without the help of Daddy's drug. I had to take my time, working my way down gradually, greatly assisted by Daddy's hand squeezing my breast and his thumb rubbing my clit. I wasn't quite sure where it all went, honestly... but looking down at my tiny little belly, I could barely even see a bulge, even with all nine inches lodged fully up inside! I took a few minutes just to explore, rocking and rolling my hips, feeling him moving around inside of me, pressing against all my different spots.

I started to bounce. Just a little, at first, barely even an inch. But it felt so incredible, and he was responding to it so eagerly, it wasn't long before I was supporting myself with my hands on his chest, throwing myself up and down his thick, solid shaft just as hard and fast as I could! That was when the heat really started to build, which drove me to even greater extremes. Not for the first time, it was a good thing Daddy had more experience than me—when I started to cum, I swear I would have tossed myself right off the end of his dick, if he hadn't seen it coming and grabbed my hips to hold me in place! I tried to resume what I'd been doing... but every time I moved it sent aftershocks coursing through me, making my thighs tremble uncontrollably and interfering with my rhythm.

“I think maybe you'd better roll me over and fuck me after all, Daddy,” I giggled, giving up and collapsing onto his chest, nuzzling against his neck.

“Gladly, baby, if that's what you want,” he agreed with a grin. “But what would you say to trying out doggy style first, instead?”

“Ohhh!” I purred with surprise and excitement. “Can we, Daddy?”

“Up you get, baby!” he laughed, patting me on my ass. He helped me into just the position he wanted, with my face down against the mattress and my knees spread, placed slightly in front of the line of my hips to make my cute little butt stick right out at him in the air. He got into place behind me, playfully slapping himself against my wet, swollen pink lips. I obediently whimpered and shimmied my hips, until he rewarded me by sliding himself in, bottoming himself all the way out in one huge, forceful thrust!

“Daddyyy!” I squealed. I tried to lift myself up, but he leaned forward with a hand between my shoulder blades, forcing me right back down as he started fucking me hard and deep. What he was doing didn't actually hurt, I soon realized... at least, not any more than when I'd been doing pretty much the same thing to myself only moments before. It had just taken me by surprise, was all. But if this was the kind of sex he was in the mood for this morning...

“Ohhh, pull my hair, Daddy!” I moaned for him. I'd never tried anything like this myself, of course... but I'd watched plenty of porn, to know how it was supposed to work, what I was supposed to say. And... I knew what it was supposed to feel like, from my experiment last night; I found it shockingly easy to slip back into the proper frame of mind. “Pull my hair and spank my ass, Daddy! Fuck me hard! Punish your daughter's naughty little teenage pussy with that huge, hard Daddy cock!”

“Oh yeah?” he asked. I couldn't see his face at the moment, but I could hear the wicked, predatory grin in his deep, sexy voice. He wrapped his hand into my long blonde hair, making me gasp as he pulled. “Is that what you like, you little slut?” He spanked me, hard, making me yelp, then whimper as he gripped my newly-sensitive flesh where he'd struck me. “You like taking Daddy's cock?”

“I love it, Daddy!” I wailed. “I'm your good little girl! I love pleasuring Daddy's cock!”

“Yeah you do!” he agreed, spanking me again. “You're such a good little whore!”

“I am, Daddy! I am!” I gasped, my thighs trembling—not from impending orgasm, which I could tell was still at least a few minutes away, but just from pure, unmitigated arousal at what Daddy and I were both saying. “You can do anything to me, Daddy! I'm your obedient little fuck-doll whore! I'll do anything you say!”

But we didn't say a whole lot, after that. As hot as it was to play those roles together, it was just too much effort simply trying to breathe, never mind trying to speak. Daddy was still pulling my hair a little, and I still got occasional spanks—especially every time he made me cum for him, which heightened my orgasms' intensity even more! But finally it was time, and Daddy let go of my hair to grab hold of my hips, pounding in hard and delivering his amazing, incestuous gift, filling me up once again. He wavered behind me, unsteady on his knees, until he finally pulled out and collapsed onto the bed, rolling onto his back. I snuggled in close at his side, throwing my leg over his and nuzzling into his chest, running my fingers through his soft, sweaty chest hair as we struggled to catch our breath.

“That was amazing, Daddy!” I purred. “I can hardly believe it's possible, I thought for sure it had to be your drug affecting me somehow... but that was every bit as incredible as it was last night!”

“Glad to hear it,” he chuckled, squeezing me close under his arm and softly kissing my hair. “And for me too, obviously! You are phenomenal, sweetie! I hope you know that!”

“Thanks,” I giggled, shy but proud. I was sure I still had lots to learn... but it made me so happy knowing I'd been able to pleasure him like that! “So... what do you think? Rest a bit more, then breakfast? I'd really like to try taking a shower together, if that's okay? Then after that, it'll be time to dope me up again?”

“A shower sounds great, sweetie... and very much needed, for us both!” We both laughed at that, acknowledging the simple truth. I loved the way he smelled right then, so hot and sexy... but I knew that once our sweat and cum started to dry, that would be something else. “But then it's a trip to the pharmacy, I'm afraid,” he sighed. “Cumming in you was amazing... but you aren't on birth control, so a morning-after-pill it is. And we need to pick up enough condoms to tide us over until we know you're safe. I'll call and set you up an appointment, just as soon as I trust myself to stand up again.”

“Do we really need to, Daddy?” I hesitantly dared to ask, nervously biting my lip as he twisted to look down into my eyes. “I mean... Mom wasn't that much older than I am when she got pregnant with me, right? So... what if we don't do any of that? And we just let nature take its course?”

“You can't be serious... are you, baby?” he asked, shaking his head in obvious disbelief.

“I mean... you know how much I've always wanted to be a mommy... to have babies of my own,” I reminded him, my cheeks flushing into a brilliant pink blush. “And you can hardly expect me to go out and have them with some other boy, when I could be having them with you, instead! Please, Daddy? At least think about it, okay?”

He didn't speak, for long enough that I was starting to get worried. Had I brought it up too soon? Maybe I should have waited, and had sex with him a few more times before I brought it up as a possibility.

“You realize that means no more of my drug, as long as you're at risk of getting pregnant, or while you're breast feeding,” he said at last, then grinned. “Or... breast feeding our baby, at least. I'm going to want to run a test or two on your milk just to make sure, but in the monkeys it only came through in negligible amounts anyways, and given my body mass I should be completely safe. But exposing our baby is a risk we are never going to take!”

“Really, Daddy? You mean it?” I gasped, and when he nodded and smiled I threw myself up onto his chest, squealing and hugging him tight, tears of joy brimming in my eyes.

“So... you have a choice to make, sweetie,” he chuckled, squeezing me tight and kissing my cheek.

“Ummm... yeah,” I said, sliding back down to his side and chewing my lip as I thought it over. It wasn't an easy one... but in the end it was clear what I wanted to do. “Pharmacy trip it is, Daddy. I want to give your drug some time to work... two or three months, at least. After that, we should definitely be able to see some improvement. Or if not, we can probably write it off as either not working in humans at all, or as being too slow to be worth the effort. I'll reevaluate then, depending on the results... but as of right now, I'm thinking I'll start trying to get pregnant two or three months from now, however it turns out.”

“Anything you want, baby,” he squeezed me under his arm, kissing my hair again. “But don't forget to consider the effects of pregnancy itself—that's nature's own breast-growth serum!”

“True!” I giggled, twisting and stretching up for a kiss on his lips. And I guess it was the movement of my mouth that tricked my brain into thinking I was eating, because that was exactly when my tummy erupted in embarrassingly loud gurgles of hunger.

“Breakfast it is!” Daddy laughed, patting my butt to make me roll off of him, then standing and helping me to my feet. We didn't bother to dress, we just went downstairs completely naked arm in arm, Daddy pulling me crosswise into his lap to eat our cereal together at the table.

I could hardly believe how completely our lived had changed in less than twenty-four hours. Thank God I'd decided to steal Daddy's drug! I wondered what he planned on doing with it, now that we knew about the side effect it had. That loss of control, that unbelievable need... it had been a heady thing, feeling myself getting turned into Daddy's brainless little bimbo slut like that! Not just being unable to do anything to stop it, but feeling myself losing even the desire to make it stop! For most women I was sure it would be terrifying... but there had to be others, girls like me, who would recognize it for the incredible thrill it had been! I mean... people engaged in BDSM, didn't they? Willingly placing themselves under someone else's control? Daddy's drug was a pretty extreme version of it, I'll admit... once you injected yourself, there was no more saying 'no', not until it wore off! But marketed properly, the right kind of women would pay fortunes to experience what I had! We'd just have to be super careful, keeping the formula for how to make it under strict lock and key, away from the wrong sort of people—the type of men who would inject women unwillingly!

I restrained a shudder at the very thought, smiling warmly at Daddy to reassure him that everything was still okay when he saw me doing it. I'd give him some time, before I brought it up with him. For now, we would just focus on him and me, and the new life we were going to build together. It was a shame we wouldn't be able to get married for real... but I didn't need a piece of paper, not when I had the security of Daddy's love for me, and mine for him.

“Daddy?” I asked.

“Yes, sweetie?”

“Do you think, after we get back from the pharmacy... you could teach me how to get myself ready for anal?” I felt myself blushing. “After I inject myself again... I have a feeling Bimbo-Madi is probably going to insist. And I'd really rather not make a mess!”

“Gladly!” he laughed, reaching down to give me a solid pinch on my ass, making me squeak! I scowled at him and reached back to rub my butt, more because he'd made me make such an undignified noise than because of the actual pinch itself. But as he just sat there grinning at me like a big, goofy doofus, I couldn't help but start laughing, too!

I kissed him again, deeply, and as I closed my eyes I could already see visions of our future together stretching out before us. I was Daddy's little girl in more ways than one, now... and even in the times I wasn't doped up on his drug, I promised myself I would always give him anything he ever wanted, just like I knew he'd do for me!

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