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The Professor's Potion

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A crack AU. Two male best friends in college, Hyukjae and nerdy Donghae. Hyukjae was involved in an experiment (by professor Kim Heechul) where he turns into a voluptuous lady after taking the professor concoction. He could turn to male only after someone comes in him. So he could only ask his best friend Donghae to turn him back into a male. Donghae who had always love Hyukjae (even as a male) agreed willingly.

Chapter 24: Overload Protocol

The silence that followed was total. Not peaceful, but emptied. The frantic energy had bled out, leaving behind only the wreckage. Donghae’s lungs burned. He could smell them both on the air—sex, sweat, and that sharp, burnt ozone. His own release was cooling on Hyukjae’s thigh.

He moved first, a rustle of denim against linoleum. “The door’s open.”

Hyukjae didn’t answer. She was staring at the ceiling, one hand resting on the hard curve of her stomach, rising and falling with her still-ragged breaths.

“We need to get out of here before someone comes,” he said, forcing his voice to work. It sounded flat.

“Yeah.” Her voice was sandpaper. She pushed herself up to a sitting position, wincing. A shudder ran through her, head to toe. “Fuck, I feel… scrambled.”

He grabbed their discarded clothes, his movements robotic. He handed her her torn jeans. She stared at them for a second, then worked them over her hips, hissing as the fabric touched her tender flesh. They didn’t bother with underwear. The concept seemed absurd.

As they dressed, Donghae’s eyes kept returning to the pod. The single, jagged crack was like a bolt of black lightning across its surface. It looked dead. But minutes ago, it had been alive with impossible energy.

“Do you think he’s…” Donghae couldn’t finish.

Hyukjae followed his gaze. Her expression hardened, the familiar stubborn glint returning to her eyes. “I don’t know. And I don’t want to be here to find out.”

They moved toward the door, stepping over the slick puddles on the floor. Hyukjae’s gait was uneven, a rolling waddle of pregnancy and raw physical trauma. She leaned heavily on a lab table, her knuckles white.

Just as her hand touched the door release pad, the lights flickered. Not off. They surged, a blinding whiteness that made them both flinch, then settled back into their bland hum. But now, a new sound joined it—a low, electrical thrum coming from the pod.

Hyukjae froze. “No.”

“Move,” Donghae urged, pushing at the door.

It was too late. From the crack in the pod’s surface, a tendril of pink-silver energy, thin as a wire, snaked out. It didn’t arc or flash. It lazily, almost intelligently, quested across the floor. It touched the puddle of their combined fluids.

The result was instantaneous. The energy writhed, swelled, and shot directly toward Hyukjae. It didn’t strike her stomach. It wrapped around her ankle like a living vine.

She gasped, a sound of pure shock, and stumbled back. A jolt, not of pain but of profound, destabilizing sensation, traveled up her leg. It was a feedback loop. The residue of their frantic coupling, the biological data spilled on the floor, was being sucked back into her.

“Get it off!” she screamed, kicking, but the energy held fast, pulsing.

Donghae lunged, grabbing her arm to steady her. The moment his skin touched hers, the energy thread branched. A second tendril leapt from her ankle to his shin.

It was like being plugged into a live wire of distilled, carnal memory. He saw flashes—not images, but sensations: the hot, clutching grip of her pussy around his cock, the alien feel of her own erection in his hand, the taste of her skin. A wave of lust, sharp and chemical, flooded his system, completely separate from his own will. His body responded instantly, painfully hard.

Hyukjae cried out, doubling over. “It’s… it’s doing it again. Not the transformation. Something else. It’s… amplifying.”

Her hands flew to her breasts, cupping them through her sweater. They felt achingly full, sensitive to the point of agony. Between her legs, a fresh, hot rush of wetness soaked through her jeans. This wasn’t the violent, transformative surge from before. This was a deep, subcutaneous throbbing, a desperate, physical craving being dialed to eleven.

She looked at Donghae, her eyes wide and dark. The shock was melting, replaced by something raw and hungry. “It’s reading the mess we made,” she panted. “It thinks… it thinks that’s the program. To… to keep going.”

The energy tendrils glowed brighter, feeding on their rising panic and the sudden, hormonal storm inside them.

“We have to break the circuit,” Donghae gritted out, trying to pull his leg away. The energy held him fast. Every jerk sent another pulse of amplified sensation through him. He was drowning in it.

“No,” Hyukjae breathed, and the word was a revelation. She straightened up, her face a mask of grim resolve. “We tried to confuse it before. We overloaded it. This… this is different. It’s learning. It wants a clean dataset. A complete one.”

Her hand reached out and grabbed the front of his shirt, pulling him close. Her breath was hot on his face. “Fuck me properly. No tricks. No fighting it. Give it what it wants. A perfect, simple, breeding fuck. Maybe then it’ll be satisfied. Maybe then it’ll stop.”

The logic was insane. It was the only logic they had left.

“Where?” he managed to ask, his voice thick.

“Here. Now. Before it makes another fucking cock grow out of my elbow.”

She shoved him backward towards a clear lab table, scattering a tray of empty petri dishes. They shattered on the floor, a sharp, percussive accompaniment. She turned her back to him, bent over the cold metal surface, and yanked her jeans down again. The sight was a sledgehammer to his restraint. The curve of her ass, the wet, dark cleft already glistening—it was an obscene invitation.

The energy threads hummed, approving.

He was on her in a second, his own jeans shoved down past his hips. He didn’t prepare her. She was drenched, her body screaming its readiness. He aligned himself and pushed in, a single, deep, penetrating stroke that buried him inside her to the root.

Hyukjae screamed, but it was a scream of relief. Her fists pounded once on the metal table. “Yes! Fucking… yes! That’s it!”

He set a punishing rhythm immediately, each thrust a hard, focused punctuation. This wasn’t about confusion. It was about conquest. About filling her so utterly there was no room for error, for stray energy, for anything else.

“Tell it,” she moaned, her cheek pressed to the cold table. “Tell it what you’re doing.”

“I’m fucking you,” Donghae growled, the words ripped from him. The energy tendril around his leg seemed to pulse in time with his thrusts.

“Say it filthier.”

“I’m shoving my cock so deep in your cunt it hits your fucking womb,” he snarled, gripping her hips, slamming into her. The vulgarity was a weapon. “I’m claiming this. Every fucking part of you this experiment made. This pussy. This ass. This belly. It’s all mine.”

“Yes!” she sobbed, pushing back desperately to meet him. “Breed it! Breed this fucking experiment out of me! Put a baby in me that’s just you!”

Her words unlocked something feral in him. He leaned over her, one hand snaking around to palm the heavy weight of her pregnant stomach, the other tugging at her hair to tilt her head back. His thrusts became shorter, harder, deeper, aimed with brutal precision.

“It’s mine,” he chanted into her ear, his voice raw. “This hole is mine. You hear the energy? It’s hearing this. It’s feeling you get filled up with me.”

Hyukjae was babbling, a stream of filthy, encouraging curses dissolving into wordless cries. Her body was clenching around him in tight, rhythmic spasms, her internal muscles fluttering in a cascade of building orgasm that felt amplified, magnified by the energy feeding off them.

Donghae felt his own climax coiling, a pressure building at the base of his spine. He drove into her one last, final time, hilting himself so deeply he felt the impact against her cervix, and let go.

His release was a violent, protracted jetting, pulse after pulse pumping into her depths. He growled, an animal sound, as he emptied himself.

As he came, the energy tendrils flared with a blinding, white-hot light. Then, with a sound like a sigh, they dissolved. The hum cut off. The tendrils vanished from their skin, leaving only a faint, tickling sensation that faded instantly.

The only sounds were their heaving breaths and the soft drip of something from the edge of the table.

Donghae slumped over her, spent. Hyukjae trembled beneath him, her body still pulsing with aftershocks.

Slowly, carefully, he pulled out. A thick trickle of his semen followed, dripping down her inner thigh onto the shattered glass below.

This time, no transformation happened. No new limbs appeared. Her belly just shifted slightly, a normal movement. The frantic, craving ache had subsided, leaving behind a deep, physical exhaustion and a profound, unsettling satiation.

She pushed herself upright, turning to face him. Her eyes were clear, but haunted. “It’s quiet.”

He nodded, pulling his pants up. He felt hollowed out. “It got its dataset.”

A metallic creak made them both jump. They turned to look at the pod.

The crack had widened. Just a hair. And from within the darkness of the fissure, a single, green light began to blink. Steady. Rhythmic. Like a heartbeat. Or a timer.

Hyukjae looked from the pod to Donghae, then down at her own stomach. She placed a hand over it. “We need to find Heechul’s notes. The real ones. Not what’s in the computer.”

“Why?”

“Because this isn’t over,” she said, her voice utterly drained. “And this baby… I think it just kicked harder than it ever has before.”

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