Chapter Text
Back in the lab, Seungmin discovered that his cells had behaved beautifully in his absence. Changbin’s, meanwhile, had apparently chosen death.
“Fuck. Fucking unbelievable.” Changbin shoved a hand through his hair as he peered into another flask. “One flask alive. One. And it’s the control.”
His voice echoed through the tissue culture room dramatically enough that Seungmin was mildly concerned security might intervene. A week ago, he would have ignored him. Now he found himself stepping closer automatically.
“Let me see?”
Changbin looked up, frustrated and exhausted all at once. “They’re dead.”
“Your optimism is inspiring.”
“They’re dead, Seungmin.”
“Move.”
Changbin huffed but surrendered the microscope. Seungmin leaned down, adjusting focus carefully. Mostly debris. Definitely not promising.
Then.
“Oh.”
“What?”
“There.” Seungmin’s pulse kicked unexpectedly with triumph. “Tiny cluster at the edge. They’re alive.”
Changbin crowded into his space instantly, shoulder brushing Seungmin’s as he looked through the scope.
“Oh my God.” His entire face transformed. “These are the partial knockouts.”
His grin hit Seungmin like a lorry.
“You genius.”
Before Seungmin could process that sentence properly, Changbin turned back toward him with wide hopeful eyes that should not have been allowed on someone that intimidating.
“Do you have any extra growth medium?”
Seungmin blinked once. Then twice. Ridiculous.
“Yeah,” he said quickly. “I made a fresh batch this morning. You can have 500ml.”
Changbin’s expression softened into something dangerously sincere. “You’re actually my favourite person today.”
And that did something unpleasantly fluttery to Seungmin’s internal organs.
They worked side by side after that in easy silence, passing pipettes back and forth, labelling flasks shoulder-to-shoulder beneath the sterile glow of the hood.
It was comfortable. The peace lasted exactly twelve minutes before Minho stormed into the room radiating fury.
“Have either of you seen Hyunjin?”
Seungmin and Changbin looked up simultaneously.
“He turned off my PCR machine early,” Minho said tightly. “I’m going to kill him.”
Changbin, who had screamed over dead cells less than twenty minutes earlier, somehow found the moral authority to say, “Bit dramatic. Think he was in the lab though.”
Minho glared at him.
“See you at coffee,” Changbin added quickly.
Minho exited with the fury of a man moments away from committing a crime.
At tea time, they heard him before they saw him.
“Hwang Hyunjin!”
The entire room went silent.
Hyunjin physically recoiled. “I said I was sorry!”
“I’m gonna autoclave you!”
“I thought it was finished!”
“You unplugged the machine, Hyunjin!”
“I’ll redo the entire thing!” Hyunjin said desperately. “I’ll stay late, I’ll remake the primers, I’ll buy you dinner…”
Minho crossed his arms, still visibly furious.
“…What kind of dinner?” he asked after a beat.
Seungmin watched Hyunjin’s eyes narrow instantly in suspicion. And beside him, Changbin snorted into his coffee so hard he nearly choked.
Another Monday, another lab meeting, and Seungmin was beginning to suspect that academic science was just a socially acceptable form of psychological warfare. At least his presentation had gone well. Professor Park had nodded through most of it, only interrupting twice to suggest additional controls and once to ask whether Seungmin had considered expanding the assay conditions. Which, translated from Professor Park-ese, was essentially a standing ovation.
Changbin’s work, unfortunately, was less standing ovation and more public execution.
“So,” Professor Park said slowly, steepling his fingers together, “you’re telling me you successfully generated double knockouts.”
Changbin shifted in his chair. “Yes.”
“And the cells survived.”
“…Technically.”
“Despite losing their arginine metabolism pathway.”
“Yes, but”
“And without supplemental ornithine in the media.”
A silence descended over the room. The kind that felt heavy and humid and vaguely fungal. Somewhere outside, rain tapped against the windows in smug little bursts.
Changbin swallowed visibly. “Their motility is severely impaired.”
“But not lethal.” Professor Park leaned back in his chair, expression sharpening with interest rather than sympathy. “Which raises the obvious question of whether this pathway is a viable drug target at all.”
Seungmin winced. Across the table, Minho had the expression of a man witnessing a traffic accident in slow motion. Hyunjin was staring at his laptop with suspicious intensity, as if he could project himself out of the room through the sheer force of his mind. The rest of the lab had suddenly become deeply fascinated by literally anything else. The tabletop. Their notebooks. The slightly deranged-looking pigeon perched outside the window.
“Might be worth terminating the project entirely,” Professor Park continued thoughtfully. “Or perhaps having someone else repeat the knockouts to confirm they’re genuine.”
“No!” Changbin blurted.
The word cracked through the room. He cleared his throat immediately, ears flushing pink. “I mean - I’ll resequence everything. Check the strains again before we make any decisions.”
Professor Park gave a noncommittal hum. Which, from him, was somehow worse than yelling. By the time the meeting ended, Changbin looked approximately three minutes away from either vomiting or setting something on fire. Possibly both. He stormed out of the conference room with enough force to create a minor breeze in his wake. Seungmin watched him go, chewing absently on the inside of his cheek.
Because the thing was - Changbin’s data didn’t make sense. And Seungmin hated data that didn’t make sense.
Several hours later, Seungmin was crouched cross-legged on the floor of the library stacks surrounded by papers, full of coffee, and what was either the onset of scientific inspiration or caffeine-induced psychosis. Honestly, it could go either way. He flipped through another paper, eyes snagging on a figure. Wait.
His heart gave a tiny, electric jolt. Compensatory mutations. He sat up so quickly he nearly smacked his head against the shelf behind him.
“Of course,” he whispered to nobody.
The idea unfolded rapidly after that, pieces clicking together with dizzying speed. If the cells were compensating for the loss of the original enzyme through mutations elsewhere in the pathway… He scrambled for a pen, annotating the margins furiously.
By the time he finally printed all the papers and sprinted back to the office, adrenaline buzzing under his skin, the corridors were dark and deserted. The office lights were off.
“…Oh.”
Seungmin stopped short in the doorway, chest heaving slightly. Right. It was nearly midnight. He stared at the empty room for a moment, disappointment sinking into him with embarrassing force. Then he sighed, stuffed the papers into his bag, and headed home.
The next morning, Changbin looked exactly like someone who had slept four hours and spent all of them losing arguments with himself. He was slumped over his laptop when Seungmin burst into the office.
“Ooh, Changbin,” he said brightly, unable to contain himself. “You’re exactly who I wanted to see.”
Changbin blinked up at him slowly. “That sentence usually means I’m about to suffer.”
“No, this is good suffering.”
“That’s not reassuring.”
Seungmin ignored him and grabbed his sleeve. “Come with me.”
Changbin allowed himself to be dragged into one of the meeting rooms with the weary resignation of a man accepting his fate. The second the door shut, Seungmin spread the papers across the table.
“Okay. So. You know how your knockout strains survived?”
Changbin nodded cautiously.
“I remembered reading about compensatory mutations in essential pathways.” Seungmin’s words began speeding up the way they always did when he got excited. “Basically, cells adapt to gene loss by mutating analogous enzymes to partially restore function, and I started wondering whether something similar could be happening here.”
Changbin straightened.
Seungmin shoved one of the papers toward him, practically vibrating. “Look at this enzyme. Sequence similarity, structural overlap, same substrate class - if your strains developed mutations here, it could explain the residual viability without disproving pathway essentiality.”
Silence. Changbin stared at the paper.
Then at Seungmin.
Then back at the paper again.
“Oh my God.”
“I know!”
“You actual genius.”
Heat rushed into Seungmin’s face. “I mean, maybe? It’s just a theory.”
“No, this is brilliant.” Changbin looked increasingly alive with every passing second, like someone jump-starting a dead battery. “Why did none of us think of this?”
Seungmin shrugged, suddenly self-conscious. Changbin flipped another page.
His eyes widened. “Wait. Did you already design primers?”
“…Maybe.”
“You designed primers?”
“I got carried away.”
Changbin made a strangled noise that sounded suspiciously fond. Then he laughed. Actually laughed. The sound hit Seungmin squarely in the sternum.
“Seungmin,” Changbin said, running a hand through his hair, “if you weren’t technically my student, I’d kiss you.”
Everything inside Seungmin abruptly stopped functioning. Changbin, meanwhile, seemed entirely unaware of the catastrophic damage he’d just inflicted. He was already gathering the papers together, energized for the first time in days.
“I’m ordering these primers immediately,” he announced, grinning as he headed for the door. “Thank you!”
The door clicked shut behind him. Seungmin remained frozen in place. Kiss you. Very interesting that his brain had apparently decided to latch onto those two specific words instead of, say, the groundbreaking scientific insight. Which was inconvenient. Because he was beginning to suspect he might have a teeny tiny crush on Changbin.
And unfortunately, unlike the gene mutations, there was no reliable protocol for eliminating that particular condition.
“You’re smiling at your sandwich,” Felix observed.
Seungmin immediately stopped smiling at his sandwich.
“I’m not.”
“You are,” Jeongin said. “It’s deeply unsettling.”
The three of them were crammed into the crowded campus café during their lunch hour, surrounded by the usual soundtrack of hissing coffee machines and academic despair.
Felix pointed at him accusingly with a soggy chip.
“Changbin mentioned you helped save his project.”
“I did not save his project.”
“He was talking about you like you discovered penicillin.”
Seungmin nearly inhaled his drink.
“That’s a bit dramatic.”
“Mm.” Jeongin leaned back in his chair. “Counterpoint: you’re blushing.”
“I am not.”
“You literally are.”
Seungmin pressed both hands against his face. Traitors. His entire circulatory system was full of traitors.
Felix gasped suddenly. “Oh my God. You like him.”
“No.”
“You hesitated.”
“I did not hesitate.”
“You absolutely hesitated.”
Seungmin groaned. “Fine. Maybe a little bit.”
Felix slapped the table triumphantly.
“But it doesn’t matter,” Seungmin continued quickly. “He’s still getting over his ex, and he supervises half my work, and there should be lines. Professional ones. Important, healthy boundaries.”
Jeongin hummed thoughtfully. “You know, for someone committed to professionalism, you do spend an awful lot of time staring at him when he’s not looking.”
Seungmin choked on air.
Felix looked delighted. “Oh, this is better than television.”
“And,” Jeongin continued serenely, “Changbin definitely likes you back.”
“That is objectively untrue.”
“Please. He barely tolerates most people. Last week he brought you coffee without being asked.”
“…That was because he was already getting one.”
“He remembered your order.”
Silence.
“Oh,” Felix whispered dramatically. “Oh, you’re doomed.”
“Can we talk about literally anything else?”
Jeongin grinned a shit eating grin. “Fine. What’s going on with Minho and Jisung?”
And just like that, the conversation dissolved into gossip. Seungmin was profoundly grateful. Mostly because he was starting to think his friends might be right. Which was horrifying.
A week later, Seungmin was still in the lab at nearly eleven p.m., running his cofactor binding assay for the third time in three days. At this point, the experiment felt less like science and more like torture. His eyes burned from staring at fluorescent readouts all day. His shoulders ached. But he couldn’t stop. Because this run might work.
And if it didn’t. Well. He’d probably cry quietly in the cold room for five minutes and then try again. Character building. Seungmin added the final reagent with exhausted precision, loaded the sample into the machine, and hit start.
The screen flickered. A line began crawling across the graph.
Flat.
Flat.
Flat…
“Come on,” he muttered.
Then suddenly.
The curve rose.
Seungmin stared at the screen in complete disbelief.
The curve was rising.
Actually rising.
For one long second, he genuinely wondered whether sleep deprivation had finally driven him into full scientific hallucination territory. Which, frankly, would not have been shocking. He had been living almost exclusively on canteen coffee and nerves for the past week.
But no.
The graph continued climbing steadily upward.
“Oh my God,” he whispered.
His chair scraped loudly against the floor as he stood up too fast, heart thundering somewhere near his throat. The fluorescent lights above him buzzed faintly, the machine hummed, and Seungmin felt suddenly, bizarrely light-headed.
It was working. His assay was working.
Not wanting to trust himself (or the universe) just yet, he immediately printed the results and reset the apparatus with trembling hands. Because one successful result meant nothing. Science required replication. Preferably in triplicate. Ideally accompanied by statistical significance and emotional resilience.
Seungmin currently possessed neither of those things. The second run started. He stared at the screen so intensely his eyes began watering. The line stayed flat for one horrible second.
Then…
It rose again.
“Oh my God,” he said louder this time.
His enzyme worked. His actual, stupid, impossible enzyme worked. By the third successful run, Seungmin felt borderline invincible. Like he could run a marathon. Like he could fistfight God.
Energy fizzed violently under his skin as he bolted out into the corridor at nearly eleven pm, unable to contain himself for one more second.
He needed to yell. Or jump. Or maybe cry.
Instead, he attempted a cartwheel.
Now, there were a couple of problems with this decision.
The first being that Seungmin had never successfully performed a cartwheel in his life. The second being that there was apparently another human being in the corridor. Seungmin crashed directly into them with all the grace and dignity of a collapsing bookshelf.
“Oof”
“What are you doing?”
Ah. Changbin.
Seungmin looked up from his undignified sprawl on the floor to find Changbin staring down at him with a mixture of alarm and profound confusion.
“My assay worked!” Seungmin announced from the ground, grinning so hard his cheeks hurt. “It actually worked!”
For a second, Changbin just blinked at him. Then his whole face transformed. And honestly? Seungmin could probably survive on the warmth of Changbin’s smile alone for the next several months.
“That’s amazing,” Changbin said immediately, reaching down to pull him upright. “Seungmin, that’s incredible.”
His hand wrapped around Seungmin’s wrist firmly, warm and calloused, and…
Right. Okay.
Unfortunately, Seungmin was still catastrophically aware of Changbin at all times. Even while experiencing scientific euphoria. A true burden.
“I’m just heading to check my sequencing results,” Changbin continued, still smiling at him in that soft, unbearably fond way that had become a serious problem recently. “The ones you suggested. Want to come?”
“Yes” Seungmin said instantly. “Obviously.”
Changbin laughed quietly. And then they were walking side by side down the dim corridor, Seungmin practically vibrating with leftover adrenaline while Changbin shook his head affectionately beside him. The building was mostly empty at this hour. Their footsteps echoed softly against the linoleum floors, the air carrying that strange late-night laboratory smell of agar, dust, and overheated machines.
Seungmin liked nights like this. The world reduced to science and fluorescent lighting.
They squeezed into the office together, shoulders brushing briefly as Changbin slid into his chair and pulled up the sequencing files.
For a moment, neither of them spoke.
Then Changbin froze.
“Oh my God.”
Seungmin leaned closer automatically. “What?”
“Seungmin.” Changbin’s voice climbed an octave and doubled in volume. “Oh my God.”
On the screen, bright peaks lined up perfectly against the reference sequence, except for the short run they were looking for.
Mutation confirmed. Exactly where Seungmin had predicted. For one stunned second, neither of them moved. Then both of them started talking at once.
“This explains the residual”
“Compensatory adaptation”
“The pathway still matters”
“You were right”
Changbin turned toward him so quickly their chairs knocked together. And suddenly Seungmin became aware of everything all at once. Changbin’s knee pressed against his.
The sharp warmth of him at Seungmin’s side. The way his eyes looked in the glow of the computer screen - dark and bright and entirely fixed on Seungmin. Electricity crackled low in Seungmin’s stomach. Oh God. Jeongin had been right. Jeongin was never allowed to be right.
Neither of them seemed capable of looking away. Slowly, almost cautiously, Changbin’s gaze dropped to Seungmin’s mouth. Seungmin’s breath caught. The air between them shifted. It felt strange, almost unreal, how naturally it happened after that. Like gravity. Like something inevitable. They leaned toward each other at the exact same time.
And then Changbin kissed him.
Seungmin’s entire brain promptly ceased functioning. Because no one had ever kissed him like this before. Carefully, like he mattered. Like Changbin had thought about it before. As if he’d wanted to do this for a long time.
Changbin’s hand came up slowly, fingers brushing Seungmin’s cheek, then sliding behind his ear. His thumb rested lightly against Seungmin’s jaw, warm and impossibly gentle. Seungmin made a small, helpless noise into the kiss.
Humiliating. Completely unavoidable.
His own hands fisted instinctively in the front of Changbin’s shirt, dragging him closer until their chairs screeched loudly together across the floor. Some distant part of Seungmin’s brain registered how absurdly unromantic the setting was. The office was dark except for the harsh glow of sequencing data on the monitor. There were at least three empty coffee cups nearby. Something smelled faintly of LB media.
And yet this was somehow the most romantic moment of Seungmin’s entire life. Changbin kissed him deeper, slow and searching, and Seungmin felt molten with it, dizzy from the careful slide of Changbin’s mouth against his.
Then suddenly.
Changbin jerked backward. The loss of warmth felt immediate and awful.
“Oh God.” Changbin stood so quickly his chair nearly tipped over. “I can’t do this.”
Seungmin blinked up at him dazedly, lips tingling. Changbin looked genuinely panicked.
And heartbreakingly guilty. “I’m so sorry.” he said hoarsely.
“What?” Seungmin pushed himself upright. “Why?”
Changbin dragged both hands through his hair, pacing once before stopping abruptly with his back turned.
“I’m supervising your project. There are boundaries. Lines we have to observe.”
The words landed heavily between them.
“I can’t.” Changbin broke off harshly. “I can’t be this person.”
Seungmin’s chest tightened painfully. Because this clearly mattered to Changbin. Maybe too much.
“Tell me something,” Seungmin said quietly.
Changbin went still.
“Do I mean anything to you?”
For a long moment, Changbin said nothing. Then he made this awful, wrecked sound in the back of his throat.
“I can’t, Seungmin.”
Which was not actually an answer.
Seungmin stood slowly, pulse hammering again for entirely different reasons now.
“What exactly am I to you?”
Changbin turned then. And the look on his face.
Oh. That was not indifference. That was a man hanging by a thread.
“i think that you’re a line I want to cross,” Changbin admitted softly. The confession seemed dragged out of him against his will.
“I know it’s wrong.” His voice cracked slightly. “But I can’t help it.”
The words settled heavily between them.
Seungmin stared at Changbin, his pulse beating so hard he could feel it in his fingertips. Changbin looked almost angry at himself for saying it out loud, chest rising unevenly, eyes dark with restraint.
“Well,” Seungmin said carefully, because apparently his mouth still worked despite the rest of him dissolving into an emotional soup, “that seems wildly inconvenient for both of us.”
To his surprise, Changbin barked out a short laugh. It sounded wrecked.
“Seungmin,” he said, scrubbing a hand down his face. “You should be furious right now.”
“Why?”
“Because I kissed you when I shouldn’t have.”
Seungmin considered that seriously. The problem was, he was currently incapable of regretting anything that had happened in the last five minutes. If anything, his primary regret was that Changbin had stopped. Which probably said concerning things about his judgment.
“I think,” Seungmin said slowly, “that if you’d kissed me like that and I hadn’t kissed you back, we could call it inappropriate.”
Changbin stared at him.
“But I did kiss you back,” Seungmin continued. “Quite enthusiastically, actually.”
A flush climbed slowly up Changbin’s neck.
Very interesting that Dr Seo Changbin - who argued with senior researchers without blinking and once told Professor Park his statistical analysis was “emotionally compelling but mathematically weak” - could blush.
“You’re making this difficult,” Changbin muttered.
“I’m a scientist. It’s my job to create problems.”
“That is absolutely not what being a scientist means.”
“Then we’ll have to agree to disagree.”
Another laugh escaped Changbin despite himself, quieter this time. The tension in the room shifted slightly - not gone, not even close, but softer around the edges now. Less panic. More ache.
Changbin looked at him for a long moment. Then, very quietly, he said, “You have no idea what you do to me.”
And. Well.
That did things to Seungmin’s internal organs. His brain short-circuited briefly before sputtering back online just long enough to produce one coherent thought:
Oh, I’m in trouble.
Because this wasn’t a crush anymore. This wasn’t even infatuation. Somewhere between late-night experiments and coffee runs and bickering over protocols, Seungmin had apparently fallen into something terrifyingly real. And judging by the look on Changbin’s face, he wasn’t alone. Changbin took a step toward him before seeming to catch himself.
“I shouldn’t,” he said, voice low.
But he was looking at Seungmin’s mouth again. Which felt somehow significant. Seungmin swallowed.
“Then why are you looking at me like that?”
Changbin closed his eyes briefly, like he physically pained himself.
“When you ask questions like that,” he said hoarsely, “it makes me think you’re trying to kill me.”
“That seems dramatic.”
“You attempted a cartwheel twenty minutes ago. You don’t get to define what’s dramatic.”
Seungmin snorted unexpectedly. And something in Changbin’s expression softened completely at the sound. There it was again. That unbearable fondness. The kind that made Seungmin feel warm all the way down to his bones.
“I don’t know what happens next,” Changbin admitted quietly. “I just know I don’t want to hurt you.”
The honesty of it hit Seungmin squarely in the chest. Because Changbin meant it.
Seungmin stepped forward this time. Changbin immediately went still.
“I’m not asking you to figure everything out tonight.” Seungmin said softly. “I just…” He hesitated. “I don’t want you pretending this didn’t happen.”
Changbin’s gaze searched his face carefully, almost cautiously.
“As if I could,” he murmured.
Then Seungmin did something either very brave or profoundly stupid. Possibly both. He reached out and took Changbin’s hand. The reaction was immediate. Changbin inhaled sharply, fingers tightening around his instinctively. And suddenly Seungmin understood something important:
Changbin had probably been holding himself back for a while now. Long enough that even this, just touching hands openly, felt overwhelming.
“You know,” Seungmin said lightly, even though his heart was attempting escape, “for someone trying to resist me, you keep staring at me like I invented PCR.”
Changbin sputtered out a laugh.
“You’re impossible.”
“And yet.”
“And yet,” Changbin echoed softly.
The silence that followed wasn’t awkward.
It felt full. Warm. Outside the office windows, rain streaked softly against the dark glass. The sequencing data still glowed on the monitor behind them. Evidence of discovery. Proof that together, they worked startlingly well. Scientifically and otherwise. Seungmin’s eyes flicked back to Changbin’s mouth before he could stop himself.
Changbin noticed. Of course he noticed. His expression shifted instantly, restraint fraying all over again.
“Seungmin,” he warned quietly.
This time, though, the warning sounded less like no and more like please be careful with me. Something in Seungmin’s chest melted. So he moved closer slowly, giving Changbin every chance to stop him.
Changbin didn’t.
Their second kiss felt different from the first. Less startled. Less desperate. Intentional.
Changbin touched him like something precious, one hand sliding carefully along Seungmin’s jaw while the other settled at his waist, pulling him close enough that Seungmin could feel the rapid beat of his heart through his shirt. Which was deeply satisfying, honestly. Good to know he wasn’t the only one barely surviving this. Seungmin kissed him back slowly, smiling helplessly when Changbin made a quiet sound against his mouth.
The office around them faded away - the ugly carpet, the humming computers, the abandoned coffee cups.
There was only this. Warm hands. Soft breaths. The dizzy certainty that something important had just changed. Eventually, Changbin rested his forehead against Seungmin’s, both of them breathing slightly unevenly.
“We’re going to have to talk about boundaries,” he murmured reluctantly.
“Probably.”
“And professionalism.”
“Ugh. Horrible.”
Changbin laughed softly, eyes crinkling at the corners.
Then, before he could stop himself, he said, “I think I’m falling in love with you.”
Silence. Absolute silence. Changbin blinked.
“Oh my God,” he said faintly. “I was not supposed to say that out loud.”
Seungmin’s heart nearly exploded on the spot.
Unfortunately for everyone involved, his mouth reacted before his brain did.
“Good,” he blurted. “Because I'm starting to think I’m already on my way there too.”
Changbin stared at him. Then he smiled. Not the teasing smirk Seungmin knew so well. Not the amused little huff he gave during arguments. This smile was different. Open. Bright. Hopeful.
And suddenly Seungmin understood that whatever happened next - awkward conversations, complicated lab politics, figuring out where the line actually was - they would figure it out together. Changbin squeezed his hand once, still smiling at him like he couldn’t quite believe this was real. Neither could Seungmin. But for the first time in a long time, the future didn’t feel frightening.
It felt exciting.