Mutual Development

"Hey, Nicky, turn around and show me those jeans?"

Nick sighed, turning around from the sink. He hated when she called him Nicky, and she knew it.

"What's up, Kate?"

Kate looked down Nick's slim body, biting her lip. "Are those jeans... A little small on you?"

He rolled his eyes and turned back to the sink, then stood still for a moment. "Uh. Hold on. Did they shrink in the wash?"

"When's the last time you washed your jeans, Nicky?"

She pushed her chair out from the dining table and walked behind him. He felt the soft curves of her chubby body press into his back, her arms wrapping around him.

"No, Nicky, it's not the jeans. Wanna take them off for me?"

"Here?"

She responded not in words but by kissing the side of his neck, running her hands down to his crotch and giving it a light squeeze. She briefly widened her eyes in surprise as Nick gasped, his hands shaking for a moment on the dish brush, before sinking into a smile again.

"Ooh, we're playing are we? Is your cock feeling all sensitive, Nicky?"

He grunted. "I-I'm not playing, it-aauughnnn..." He shuddered as she grabbed it again, then started to pull him away from the sink. "Let's go over to the couch and see exactly what's happening to your dicky, Nicky."

He didn't protest as she led him over, pushing him down and starting to slide down his jeans. Nick wore plain white briefs over what, if he was being truly honest, was an unimpressive five-inch endowment.

Normally.

"Whoa! Check it out, Little Nicky!"

His underwear was strangely full – and a little moist. Kate brought her hand up, testing the weight with a palm, making him draw in a sharp breath. She watched intently, and her mouth dropped open as she watched his package expand a little before her eyes, the elastic stretching across new flesh.

"K-kate, did it just-gggguh!" Kate squeezed hard, looking up at him fiercely.

"I didn't say you could talk, did I? You interrupted my fun. Don't do it again." She let go and kept watching rapturously as Nick's underwear grew tighter and tighter. He was panting and starting to sweat as the expansion became obvious to him. There was a pulsating pressure between his legs, sort of like the feeling of needing to go to the bathroom, and it came in waves and flows along with a slowly building prickling heat. His hands moved downwards but Kate slapped them away.

"Don't you dare." She caressed her nails around the expanding mass, prompting another pulsing surge of growth. "This is incredible. I have no idea why this could be happening."

Kate was a terrible liar. "Kate, what did-ggggauah!"

She squeezed again, hard. "No talking."

By now his briefs were stretched tight over his growing manhood, cutting into the soft flesh. Every inch of his expanded genitals were outlined against the fabric and his testicles were starting to bulge out of the sides. There was a faint gurgling sound issuing from them, like an upset stomach.

Nick gasped as there was a ripping noise and one of the seams split, prompting a contented moan from his lover. She grabbed either side of the burst seam and tore them open, letting the full extent of his swollen junk fall out against the couch with a heavy thud.

His dick was six inches long, even though it was fully flaccid. A clear fluid was dripping from the end, where his bloated, puffy foreskin was bunching up. Underneath his balls were bigger than tennis balls and radiating heat. They sat heavily in his loose, expanded sack, drooping down over the side of the couch. Kate gripped his cock by the base and flopped it from side to side a little bit, staring at Nick with deep eyes past the flaccid tube of his meat.

"Wow, Nicky, you're so big now. You must feel so huge and manly and in control now, right?" She leaned in and nibbled at the doughy foreskin, sliding her tongue past it to nestle just at the tip of his cock, making Nick shriek and buck, his hands gripping the couch cushions tightly.

"Fuck, Kate! It's too-aaauigh!"

She'd squeezed one of his balls at the same time as biting lightly on his foreskin and squeezing into the spongy shaft, looking up at him and giggling. His cock was pulsing madly, like it was going erect, but instead of getting hard it was growing longer and fatter with each passing moment. His balls were expanding in the same heartbeat fashion, the previously faint gurgling noise now audible throughout the room, groaning and churning. Kate pulled back for a moment to slip off her shirt and then unhook her bra, grinning up at Nick as her fat, pale tits fell down and flattened across her chest, freckle-dusted and capped with thick pink nipples. She grabbed them and held them up, her nipples pointing straight at Nick, gently separating and mashing them together in circular patterns.

"Okay, pet. I want that big twitchy cock to get hard for me so I can have some fun."

"Kate, it's too much, I don't think I-" he squeaked, cut off short as Kate grabbed one of his balls with a serious, unamused expression.

"Again, pet, I didn't ask you to talk or think, did I? I want you to apologise for interrupting me."

His brow wrinkled until she squeezed again, making him yelp. "I'm sorry!"

"From now on you will refer to me as Mistress until I tell you otherwise. This giant cock is too ridiculous for you to be anything but a play pet, so you're going to behave like one. Understood?"

He went to reply but seeing Kate's expression thought better of it. "Y-yes."

"Yes who?"

"Yes mistress?"

"Good. Now, before that silly little display I was going to put your stupidly huge dick between my big, soft, fat titties and rub it until it got hard for me. But you don't deserve titties any more, not until you learn to behave. Get on the floor."

He slid off the couch, gasping as his balls swung out of control, slapping against his legs and then the carpet. His cock swayed from side to side, flicking off small gobs of fluid.

"Be careful with those ridiculous livestock balls, you klutz! I've got plans for those. On the floor!"

Red-faced, Nick laid down on the floor, his genitals still aching and pulsing with growth. His cock flopped down across his stomach leaving a gooey trail. His legs had to spread slightly to make room for his testicles. Kate strode over him, now completely nude, staring down at him from over her tits and stomach, before she turned around and planted herself straight onto his face.

She wiggled, mashing the hot cauldron of her fat pussy and chubby thighs into his face before picking up his rubbery dick with a free hand. "Go on, fucktoy. You lost titty privileges, so this is what you get until I'm satisfied that you're very sorry for interrupting me."

He desperately started to lick, making Kate take a deep, rattling breath before she began exploring his still-growing cock. She held it upright, eyes wide with awe at how far up it reached completely flaccid, then bit her lip as she watched it pulse and swell again.

"Wooow, it's still going. They really didn't lie about how well those droplets would work."

She heard a questioning noise from underneath her pussy and squeezed her thighs until it stopped. She thought for a moment, then raised her hips off Nick's face, letting him catch a few desperate breaths until plunging back down again.

Holding his cock up with one hand, she used the other to start gently peeling his moist, sticky foreskin away from the tip. The glans she revealed was bright red and hot, and even just gently blowing on it prompted a muffled shriek from her boyfriend underneath her, as well as an extra-loud groan from his overstuffed balls. She leaned forward and gripped it at the base again, letting the whole flaccid length flop down and slap against his stomach, Nick twitching and shuddering underneath her with the sensation, before dragging her hand back up it to slide the skin back to where it had started.

She felt it twitch, not the pulsing she'd been feeling of his growth but a different sensation, and her lips curled into a smile. One more slow, lascivious stroke, combined with another wiggle on his face before letting him get some more air, and his cock was definitely a bit more rigid than it had been, and a lot bigger. He shuddered and moaned and whined like he was in pain, but he couldn't stop himself from slowly starting to grow erect. Kate treated herself to the delicious sensation of him screaming into her pussy by gently probing the slit of his dick with her tongue.

It pulsed and swelled rapidly now, combining his growth with the march towards erection. His balls were growing even faster to match, each one now the size of a cantaloupe. His scrotum was expanding to make room, and with his balls bunched between his legs they swam in a mass of soft, wrinkled skin. Kate slid forward along his body, hearing him gasp behind her ass, until she straddled his torso and could pull his hardening cock up against her.

She pulled the shaft against her stomach and nestled it between her breasts, then reached down around it and lifted up his bloated testicles, rubbing her hands into them to indulge in the plush texture of his new scotrum. They gurgled audibly and, for their size, were ridiculously heavy. She let the mounds fall out of her hands, observing how the loose folds of spongy flesh stretched out from the sudden movement of weight. Leaning past his shaft she pushed her face into the mass, rubbing her cheek against it, taking a deep breath. His pained whimpers from behind her only added to her fun.

"They're sensitive, aren't they, pet?" She lifted one back up and gently bit into it, shuddering as he whined. "God, they're so loud and heavy. They're all full, aren't they pet? Stuffed full to the brim with load after load of thick subby cum?"

He could only moan in reply, his mind being carpet-bombed by the oversensitive flesh that had sprouted between his legs. They were heavy though, and so full that they ached with pressure. She returned her focus to his cock, now almost fully hard, as thick as a soda can and projecting up to her breastbone.

"Now that's a fuckstick worthy of my toy. No offense, Little Nicky, but you've always been just a little bit disappointing down there, and while it was fun humiliating you about it you know I've always been a bit of a size queen."

She gripped it in one hand and started to lazily stroke, feeling Nick writhe underneath her as he whined. "I mean it is a shame that your big new fuck-pole is so oversensitive that it's completely out of your control and there's no way you'll ever be able to do anything with it aside from be played with by me, but that's a small price to pay for my entertainment, isn't it?"

Even if Nick had been game to speak back to her, he wasn't capable of it. The feeling of Kate just gently playing with him was enough to shut down all of his higher-order thoughts. It was like an off-switch for his brain. Kate let her tits droop around it, then wrapped one hand around to hold them together into a canyon of sweaty cleavage that grabbed at the thick skin of his dick and started to rub it up and down against the shaft.

"Go on, pet. I want to see you cum. That's all you're good for now, isn't it? Getting hard and shooting cum everywhere like an animal? You know you want to. Just admit it and cum."

He wanted desperately to object. His brain tried to rally some sort of resistance, even just a response, but his thoughts were slow and muddy, his brain being dragged through a hot pink fog of pure pleasure. All he could feel was the dull thud in his oversized cock and the ache in his swollen balls, like every other sensation had been switched off to provide more room for every inch of his shaft.

Kate was grinding her whole body against it now, squeezing the base with her thighs, rubbing her belly against the middle and fucking the top with her tits. Suddenly Nick's eyes flew open, a low, gravely moan rose from his throat and his hips began to buck as his whole body tensed in expectation. His balls groaned even louder, overlaid with the sound of thick fluid being pumped and churned, like the sound of an emptying bathtub drain.

It took a few seconds of exquisite agony, and then cum fountained from the end of Nick's cock in the most spectacular cumshot Kate had ever seen. In just a single pump enough cum to fill a soda can sprayed hard enough to hit the ceiling. Another pump, then another, and another, Nick squealing as his balls unloaded more spunk than Kate had ever seen in her entire life. She let it spray across her face and chest, indulging in the sensation of the hot slime on her skin, letting it slide down her throat, but mostly just watching as it fountained in endless ropes across the room.

A full minute later the crippling spasms finally stopped and Nick just lay there, near-comatose, spunk coating him like the world's worst glazed doughnut. His balls had settled back into a more even gurgling noise, having stopped growing once they reached the size of soccer balls. His cock, though, was still steel-hard, so much so it could barely throb, beet-red with the pressure inside it. Kate's eyes lit up and she retrieved a small bottle from a nearby cupboard, feeding three drops of fluid into her mouth.

"That was incredible, pet. I'm glad you're still hard, though, because you are not even close to done." She stood over him again, pulling his cock down until the tip could kiss her pussy, gently rubbing herself against him until his dick was practically leaping at her.

"You're going to fuck me."

He looked up at her, and then downwards at the oversized log of his expanded cock. "B-but, I... you can't..."

"Don't tell me what I can and can't do, fuckpole."

Juices glistened at her entrance, her breathing rattling as she kept rubbing herself against his tip, until she seemed to decide she was done and pushed. He slipped inside her, drawing a shuddering gasp.

"Oh fuck, that's... Mmm..."

She wiggled her hips, moaning, sliding more of him inside her bit-by-bit. She stopped periodically, letting herself acclimatise, giving the drug she took more time to work its magic inside her. Nick grunted and twitched, her pussy stretching around his oversized dick and squeezing down on every inch of the oversensitive pole with a torturous flood of feeling.

Kate gasped exultantly as he finally bottomed out inside her. She placed her hand on her stomach, following it up, trying to work out how the drops had let all of this fit inside her and visibly giving up and focusing on starting to rock herself against him. She gripped her fat breasts, holding them in place as she pushed her legs to slowly rise up, before letting herself drop back down, getting into a slow but determined bouncing cowgirl rhythm.

Mashing her hands into her breasts, feeling herself speared and spread apart in a way she could never have imagined, it only took a few minutes until she had to stop bouncing to allow an orgasm to flood her body, a full-body muscle-seizing set of spasms that left her eyes rolling and her mouth slack. Her pussy shuddered and squeezed, compounding the pleasure she was feeling into a feedback loop that left her almost senseless.

It took quite some time before she recovered and started to work against Nick again, and her newly-minted toy was clearly suffering. His face was bright-red, slicked with sweat, and his impossibly-hard cock could barely even throb. The pleasure had long become unbearable, an endless exquisite suffering such that when his orgasm finally arrived, he couldn't even react to it. It was just a blip in the sensation, a minor groan from his voiceless torment. However, as Kate felt his cock lurch, his overproductive testicles heralded what was coming with the loudest and fiercest noise they'd made the entire encounter, the bathtub drain sound amplified two fold, before they pumped the first shot of thick, overheated fluid inside her. She moaned in delight, rocking her hips back and forth as he kept shooting off, letting the pressure of cum build until her stomach bulged.

He gasped in pain as she raised herself off him, slowly extracting two feet of meat from inside her and letting her body react to the sudden emptiness. Cum poured from her pussy down into Nick's lap as she stood up, pooling in the soft sea of his scrotum, gobs of the stuff rolling down the side of his cock. She finally extracted herself, the fat head of his dick popping out from inside her, and swung a leg over to stand next to him, breathing heavily.

"Well that was incredible. I'm going to enjoy this new you, Nicky-toy. I mean, you don't have much of a choice, it's not like you're good for anything else with that ridiculous cock and those stupid droopy oversized balls. You won't even be able to walk without kicking them. Actually, I want to see you try and walk some time."

Nick couldn't speak as Kate walked away. His cock was still erect, still overfull and red, and it didn't feel as though it was even close to becoming flaccid again. Kate grinned as she watched it sway, giving the glans a gentle squeeze.

"Oh, yeah, those drops mean once you get it up you stay hard for hours. I think they said you're good for something like nine or ten orgasms before you go soft again? Getting more sensitive and desperate each time? Very good stuff."

As she spoke she absent-mindedly strapped on her bra again. Her brow furrowed, and she went to adjust it. "Did I pick up the wrong bra? This one feels... Ohhh..."

Her chest heaved as she took in a deep breath. Her boobs were ridiculously sensitive. "Must have overstimulated myself with Nicky. Going to have to punish him for- oooOOH!"

She felt a sick, bloated sensation in her chest, and before her eyes a slow creep of pale flesh bulged out over the cups of her bra. When it stopped, her bra looked two sizes too small for her.

"What the fuck is going on?"

Her eyes flicked to the bottle on the counter, reaching out for it to read the label.

Subjects will express the compound in bodily fluids for 24 hours. Avoid mixing with similar compounds or side-effects may occur.

She moaned again as the feeling surged in her breasts again and they expanded against her bra, more flesh spilling out over and around the cups. She reached back to unhook it and struggled to pull the hooks apart with the pressure her new volume was putting on them. It took another surge of growth and a desperate wrench to snap the hooks, letting her breasts tumble free and slap against her chest.

They pulsed with heat and sensation, the veins visible in the pale freckle-dusted skin, and free of the confines of her bra she could tell with a sinking feeling that they were absolutely, undoubtedly bigger. She was already gifted with the massive chest of a lucky overweight girl, and the last few minutes had kicked her over into absurdly big. They were fuller, too, the flabby mounds growing not just bigger but rounder, every few seconds heralding another surge of expansion. She grabbed them as if to try to slow them down but that only drew a rattling moan from her as they plumped against her fingers.

Already, between the new size and the way they were filling out, she looked twice as big as when she'd started. Her nipples were keeping pace, the mounds growing longer and thicker to match her expanding size, her areolas stretching as her flesh did. They were burning hot but also tantalisingly soft, spilling out from around her hands in plush piles that just kept growing. They hung to her belly button when she let them go now, extending a foot outwards from her body at their widest point, beginning to weigh on her back.

"P-please, no, I don't... I don't want this..."

If anything they only began growing faster in response to her pleading. Looking down she could watch them consuming her view, her feet a distant memory against the advancing wave of titflesh. She could feel their weight increasing moment-to-moment, resting further down along her body. She reached down to try and lift them up, hissing as they sent bolts of pleasure up her spine, and staggered back over to the couch. Another surge of growth and they practically vaulted out of her arms, sending her tumbling forward, lying next to Nick on the floor. In the time it took her to get on top of the sensations and gather her breath to stand back up, she realised they were too heavy. She grunted and strained, trying to get her legs under her to lift, but their unstoppable growth left her completely pinned down by the time she could move around. She couldn't even drag them now, trying desperately to heave them in any direction but only succeeding in rolling onto them, each one bigger than a beanbag chair, ripples passing through them with each motion.

"Nick! Fucking help me!"

Nick groaned, turning over, his eyes going wide as he suddenly came back to his senses and saw his girlfriend's gigantic tits. He stood up, gasping as he accidentally kicked one of his dangling balls, and observed the full extent of what had happened to Kate. They were still growing, expanding across the floor as he watched.

"What happened?"

"That stupid drug I gave you happened! Help me stand up!"

Kate was kicking helplessly, slapping at her breasts. She was more boob than woman by volume now. Her nipples alone were bigger than her breasts had started out. Their growth was slowing now, but even with that there was no way she was going to be able to move under her own power.

"Stop staring at me, asshole, and help me!"

He stared at the sea of cleavage underneath her, then down at his straining, overworked cock. He looked back up, licking his lips, and knelt down in front of her, letting his erection nestle between them.

"How many orgasms did you say it'd take for my cock to go flaccid?"

Her anger only just managed to crest the way her pussy was screaming at the feeling of his fluids leaking down between her boobs.

"Don't you dare!"

"Come on honey, I'm just going to fuck your tits until I can think again, and then I'll help you."

"Nick you asshole, I swear to God I'll- aaahuuughh!"

Her eyes rolled in her head as Nick's cock slid between her breasts. With their enhanced sensitivity the sensation was even better than the feeling of fucking him. Her tits sloshed around him as he humped them, Kate squirming and spasming in orgasmic pleasure until Nick groaned and began to unload between them, his balls groaning as he unloaded more than a gallon of spunk into her cleavage. She could feel it squishing around, leaking down, even a bit that had sprayed out past them onto her stomach. Nick let himself rest on them for a moment, cock still rock-hard, until he started to thrust again.

Part of Kate never wanted him to stop.