Accidental Hyper Muscle and Cock Growth

The hidden laboratory sat under a collapsed training ground at Konoha's edge, lantern-light sliding over steel benches and sealed glass. Kiba Inuzuka, twenty-eight, braced a crate against his hip while his colleague finished the evening's measurements. Miriam was thirty-two, a kunoichi who had traded standard missions for rogue research, and she trusted him with the work no one else was meant to see.

"Not that stand," she said without looking up. The largest vat held a thick, pearlescent amber, labeled in her tight script as hyper-potent muscle growth and male genitalia growth serum. "Full strength. If it spills, we have a problem."

His boot caught a warped grate. The crate lurched. His shoulder hit the stand, and the vat tipped before either of them could catch it.

Amber crashed over him in a hot, heavy sheet. It soaked his hair, flooded his open collar, plastered his shirt to his chest, and poured down his pants until the cloth clung to every contour of him. The smell was sharp and sweet, heated metal and warm skin.

"Kiba." Miriam stepped in and froze when he dragged in a breath.

Tingling tore under his skin, electric and tight, a live wire running through muscle. His shoulders bunched. Seams creaked along his sleeves. The wet fabric across his thighs and groin drew hard, the cloth complaining as his body began to swell beneath it. A button popped free and skipped across the stone.

Heat pooled low in his gut. He rolled his shoulders and the shirt pulled across a chest that already felt thicker, heavier, wrong in the best way. Serum dripped from his jaw onto the rising line of his pecs. His pants bit at the seams. He looked down and saw the outline of his cock pushing the soaked cloth into a shape that had not been there a minute before, thick and already growing, his balls drawing tight and heavy behind it.

His fangs caught his lower lip. Another ripple of tension climbed his arms. The crate he had dropped lay forgotten in a spreading puddle of amber.

"I'm all right," he said, and the words came out lower than he meant. "Miriam. Something's happening."

She came closer anyway, boots careful in the spill. Under the gleam of serum, muscle was bloating in real time, not the slow build of training but a violent, gorgeous swell. His biceps peaked and split what remained of his sleeves. Veins rose along his forearms, thick as cords. His chest barreled outward, striations cutting deep, until the wet shirt gave and hung in strips from shoulders that had become absurd. His neck thickened. His thighs forced the pants to tear at the outer seams, and the power in him rolled off in waves she could almost taste, strength made visible, overwhelming and raw.

Kiba growled. The sound started low in that new chest and dropped, rough and pleased, as another surge hit his groin.

His cock thickened first, shoving the ruined fly aside, then lengthened in heavy pulses until it jutted proud and ridiculous, vein-ridged, shining with serum and his own slick. The head flared broad. The shaft kept going, obscene in its size, until it stood out from his hips like something that should not have fit a human body and somehow did. His balls drew down and swelled with it, heavy, taut, filling until they hung in a grotesque, gorgeous weight between his thighs. He wrapped a hand around the shaft. His fingers did not meet. Another growl broke out of him, unmistakably hungry, hips rolling once into his own grip.

Miriam's face went hot. Arousal hit her so fast she had to steady herself on the bench. She had spent years beside him in this lab, trusted and careful, and none of that carefulness survived the sight. Extreme size. Vascular definition. Power she could see moving under his skin every time he breathed. The raw erotic fact of his transformed body made her thighs press together and her pulse slam.

"You're staring," he said. His voice was a growl now.

"I can't stop." She swallowed, and the confession came out shaky and clear. "I want you. I have wanted you for a long time, and seeing you like this—Kiba, I want all of it. Your muscles. Your cock. All of you. If you want me too."

He crossed the space in one stride. One huge hand cupped the back of her neck, gentle despite the strength thrumming through the fingers. "I want you," he said. "Say it again so I know you're sure."

"I want you. I want this. Yes."

He pulled her into a hungry kiss. She met it eagerly, mouth open, tasting serum and heat, her hands sliding up the new bulk of his chest and failing to span it. They chose it together, breathless and certain, already reaching to explore what the accident had made of him.

He used the new strength without hesitation. His hands closed under her thighs and he lifted her as if she weighed nothing at all, pinning her back to the cool lab wall. Her wrap tore under his fingers. He ripped the rest away, careful of her skin, until her clothes hung in scraps at her elbows and she was bare against the stone, panting, nodding, already reaching for him.

"Yes," she said. "Don't stop. I want it."

She got her hands on him. His cock filled both palms and still overflowed them, vein-ridged, flushed dark, the head broad and wet and leaking. She stroked what she could reach, awed, worshipping the impossible length with slow, greedy pulls while her mouth found the corded line of his throat. Lower, his balls hung heavy and hot against her wrists, grotesquely enlarged, tight with the load already building in them. She cupped them, squeezed gently, and moaned at the weight, at the way they filled her hands and then some.

"Fuck," he growled against her hair. "You feel that?"

"I feel all of it." She stroked him again, thumb dragging through the slick at his tip, and her voice went ragged with want. "You're huge. You're so strong I can barely think. Put it in me. Please, Kiba. I want you to fuck me with all of it."

He shifted his grip. He hooked her legs up and back and folded her into a standing full nelson against the wall, her knees near her shoulders, her body open and held entirely by his hypertrophied arms. Muscle flexed around her, vast and defined, veins standing out along biceps that could have bent steel. The first push was slow. She was wet and eager and still had to breathe through the stretch as that ridiculous cock sank into her, inch after thick inch, spreading her open until she was gasping his name and clawing at his forearms.

"Okay?" he rasped, holding still, shaking with the effort of not driving deeper.

"More." She nodded hard, eyes bright, completely sure. "God, more. Use it. I can take you. I want to."

He fucked her there, deep and controlled at first, then harder as her moans turned shameless. The wall thudded under her back. His muscles rolled with every thrust, power made obscene and beautiful, his growl vibrating through her chest. She couldn't move except to take him, and she didn't want to move. Submissive awe poured out of her in broken praise, filthy and devoted, while he answered with dominant, growling thrusts that bottomed out and stayed there, grinding, before he drew back and did it again.

"Look at you," he said, voice ruined. "Taking all of this. So tight around me. You love it."

"I love it." She was almost crying with pleasure. "Harder. Don't you dare be gentle now."

He wasn't. He used the strength the serum had poured into him and fucked her like the hunger in his growl demanded, hips snapping, the wet sound of it loud in the lab. They fucked like animals against that wall, raw and shaking and completely willing. Her orgasm started to build in helpless pulses. Before it could break, he carried her, still buried to the hilt, across to the nearest workbench. Papers scattered. Glass chimed. He bent her over the steel, set her hands flat, and covered them with his own so she felt exactly how much bigger he was.

Then he drew back and slammed home in a deep, pounding rhythm that knocked a cry out of her.

Doggy-style, and nothing polite about it. His hyper-muscled body curved over her smaller one, chest to her back, one arm barred across her ribs so she couldn't slip. His balls swung heavy and slapped against her with every stroke, a ridiculous, perfect weight. She pushed back, greedy, moaning for more of his power, more of the stretch, more of the way he filled her past anything she had known.

"That's it," he growled at her ear. "Take it. Take every inch. You wanted this cock, so you get all of it."

"Yes, yes, harder, don't stop."

She came first. The orgasm hit in a long, shattering wave, her cunt clenching around the thick of him, her voice breaking into a wail that echoed off the glass. He didn't slow. He fucked her through it, dominant and relentless, growling praise into her shoulder, and the clench of her dragged him over the edge. He locked his hips deep and came with a snarl, the first load pulsing out of those enlarged balls in thick, endless spurts. It flooded her until it spilled around his shaft and ran down her thighs in hot streaks. He didn't soften. The serum had left him hungry, still hard, still huge. He thrust again, slower, deeper, and spilled a second time while she shook and begged and came with him, oversensitive and ecstatic, milking every pulse he gave her. They stayed locked like that, his strength holding her up, both of them wrecked and still moving, until the last aftershock rolled through her and his growl broke into a rough, satisfied sound against her neck.

He eased out of her at last, careful, and the rush of his come down her thighs made her shiver. His hyper-muscled frame was still huge, still thrumming with leftover power, but his hands had gone gentle. He gathered her up and lowered them both to the lab floor, cradling her spent body against the broad heat of his chest. Serum and sweat cooled on their skin. She traced the still-throbbing contours of his pectorals, the ridged veins along his arm, then lower, to the heavy, half-hard length of his permanently enhanced cock and the warm, swollen weight of his balls.

"Best mistake of my life," she whispered.

"Mine too." He kissed her, slow and satisfied, breathless against her mouth. She kissed him back, fingers resting on the impossible muscle of his shoulder. For a long moment they only listened to each other breathe.

Neither of them spoke again.

The lanterns hissed softly. A last drop of serum fell from the overturned stand and struck the stone. Then the lab held only quiet.