Chapter Text
The first few months of their relationship passed with a simplicity that Sangwon found both surprising and deeply satisfying. He had expected complications. Human relationships, in his experience, were complicated by default, especially when people misunderstood each other, wanted contradictory things, and often made decisions that seemed entirely irrational. Yet being with Leo felt strangely effortless. Their conversations flowed naturally, their silences never felt awkward, and somehow Leo always seemed to understand what Sangwon was thinking before he voiced it aloud.
Sometimes it was small things.
A cup of coffee delivered to Sangwon's office after a particularly difficult morning. A text message arriving precisely when Sangwon was considering sending one himself. An extra fork being brought to the table because Leo somehow knew Junseo would steal half of Sangwon's cheesecake the moment he looked away.
At first Sangwon attributed these moments to attentiveness. Leo was observant. More observant than anyone he had ever met. He noticed details other people overlooked. He remembered things after hearing them only once. He seemed capable of cataloguing every preference, every habit, every insignificant fact about Sangwon and storing them away indefinitely.
If anyone else had done it, Sangwon might have found it alarming. But from Leo, it felt flattering.
The same observations that occasionally unsettled Sangwon became endless entertainment for his friends.
Junseo and Anxin had spent weeks listening to Sangwon insist that he wasn't obsessed with the mysterious artist from the gallery. As far as they were concerned, watching the two of them actually start dating was one of the funniest developments of the year.
"Remember when you said you weren't interested?" Junseo asked one afternoon.
Sangwon immediately sighed. "No."
"You absolutely did." Anxin insisted.
"I didn't." Sangwon denied again.
"You spent an entire month hallucinating this man's face in public." Junseo reminded.
"I was not hallucinating."
Anxin nearly choked on his lemonade. "You literally thought you saw him in a grocery store."
"Because I did see him."
"You ran across a few aisles only to realize it wasn't him.”
Across the table, Leo listened quietly while Sangwon suffered through the conversation. An amused smile appeared on his face.
"What makes this even better," Anxin continued, "is that Leo somehow remembers everything about you."
Sangwon frowned. "What is that supposed to mean?"
"It means your boyfriend remembers things about you that even we don't remember."
Junseo immediately pointed at Leo. "Tell him."
Leo looked up from his coffee. "Tell him what?"
"The weirdest thing you know about him."
Sangwon narrowed his eyes. "Don't."
Leo considered the request for approximately two seconds.
"When he reads scientific journals, he clicks his tongue when he disagrees with the findings."
The table erupted. Anxin laughed so hard he nearly spilled his drink.
Junseo pointed accusingly at Sangwon. "See? I've known you for years and I just realized that.” This earned a glare from Sangwon.
Leo smiled. "You asked."
"No, Junseo asked." Sangwon corrected.
"Still."
The conversation continued from there, bouncing between stories and complaints while Sangwon endured increasingly embarrassing examples of Leo's memory. Somehow Leo remembered the exact flavor of ice cream Sangwon preferred when he was twelve. He remembered the title of a book Sangwon had mentioned once during a late-night conversation months ago. He even remembered a childhood cartoon that Sangwon vaguely recalled discussing exactly one time.
By the end of lunch, Junseo had reached a dramatic conclusion.
"I've decided this is what happens when two obsessed people find each other."
Sangwon rolled his eyes. "I'm not obsessed."
"Right," Junseo said.
"Definitely not," Anxin added.
Neither of them sounded remotely convinced.
Across the table, Leo lowered his gaze toward his lemonade. A small smile appeared at the corner of his mouth.
For a brief moment, Sangwon thought he caught something strangely pleased in his expression.
The feeling disappeared almost immediately.
By the time the conversation moved on, he had already forgotten about it, as there were more important things occupying his attention.
His research had entered a critical phase.
For nearly five years he had been studying compulsive behavioral patterns in laboratory mice, searching for a neurological explanation for obsession itself. The project had been passed down to him by his mentor, Doctor Jo, before retirement and it begun as a simple investigation into reward pathways, but the results had gradually evolved into something much larger. If certain neural circuits could be strengthened, the brain's attachment to specific rewards became significantly more resistant to extinction, making the subjects struggle to let go.
The implications fascinated him.
One evening, after finishing dinner, he brought Leo to the laboratory. Leo had always been interested in his line of work, and through repeated insistence, Sangwon gave in and snuck Leo inside the laboratory.
The building was nearly empty at that hour. Most researchers had already gone home, leaving only the quiet hum of machinery and fluorescent lighting.
Leo followed him through the facility until they reached a room lined with observation windows.
Inside, dozens of mice moved through carefully designed testing environments.
Sangwon pointed toward one enclosure. "Watch that one."
The mouse repeatedly pressed a small metal lever yet nothing happened. Neither food or any reward appeared. Still, the mouse continued. Again and again and again. Even after 15 minutes had passed, the behavior never stopped.
Leo remained silent as he watched.
"The reward was removed yesterday," Sangwon explained. "Most subjects eventually adapt. They learn the association no longer exists."
"But not this one." Sangwon added as they watch the mouse press the level again with its tiny paws moving with mechanical persistence.
Leo tilted his head. "It knows there's nothing there."
"Yes."
"Then why does it keep on trying?"
Sangwon folded his arms. "Because expectation is stronger than evidence. The reward used to exist, so the brain continues anticipating it. At some point the behavior becomes independent of reality."
For several moments, Leo simply stared through the glass. Then a frown appeared. "I think it’s cruel.
Sangwon laughed. "It's a mouse."
"It's still cruel."
The conversation should have ended there. Instead, Leo returned to the enclosure several times before they left.
The mouse was still pressing the lever.
Months later, Sangwon's work encountered its first major obstacle.
Doctor Kim, a review committee member questioned the ethical implications of expanding his research. Meetings became increasingly hostile and funding negotiations were stalled. He seemed determined to dismantle the project entirely.
He criticized every proposal amendment Sangwon submitted. He challenged the methodology, especially its safety, and requested endless revisions.
By the end of the month, Sangwon was exhausted.
One evening he complained about it over dinner. "I genuinely think he hates me. This feels personal."
Leo looked up from his meal. "Who?"
Sangwon mentioned the committee member's name.
The conversation lasted less than two minutes before moving on to another subject.
A week later, Dr. Kim resigned unexpectedly. The official explanation involved personal reasons. No further details were provided.
Three days later, Sangwon received official notice that his research amendment had been approved.
That evening he found himself standing on Leo's balcony overlooking the city. The lights stretched endlessly below them.
For the first time in months, Sangwon felt hopeful, relieved, and happy. "I got the approval."
Leo smiled. "I know."
"How?"
"You have a very particular expression whenever you're excited."
Sangwon laughed. "Apparently you know everything about me."
"I try." Leo replied. The answer carried no embarrassment whatsoever.
The warmth that spread through Sangwon's chest surprised him. Before he could think about it, he reached forward and Leo met him halfway.
The kiss was soft. Neither of them rushed. For a brief moment the entire world seemed to disappear.
When they finally separated, Leo rested his forehead against his.
"See?" Leo whispered.
"See what?"
"Soulmates."
Sangwon rolled his eyes before he leaned forward and kissed Leo again.
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Just when Sangwon thought that things were finally moving forward, he came across Dr. He. They had been competing for the same research grant since the start of the year and it was only a matter of weeks until the announcement would be made.
It was a convention of local scientist where the met again. Each of them were given 10-15 minutes to discuss their research and convince the panel to fund it. Just as Sangwon finished his presentation, even before the moderator could ask the audience for questions, Dr. He grabbed hold of the microphone and questioned the significance of Sangwon’s research, calling it a child’s play.
Humiliation burned beneath Sangwon's skin as laughter spread through portions of the audience. Years of his work had been reduced to a public spectacle.
Still, Sangwon maintained his composure until the session ended. Only afterward did the anger begin.
That night he mentioned it to Leo. Just once. And Leo listened quietly.
The following week, disaster struck at Dr. He's laboratory. An equipment failure caused an explosion during an experiment causing three researchers to suffer injuries. Dr. He received the worst of it, acquiring 30% burn wounds leading him to be hospitalized for weeks. Due to inability to attend further sessions for the grant, his application was revoked.
Shortly afterward, the research grant was awarded to Sangwon.
That evening Leo arrived at Sangwon's apartment carrying a bottle of wine. Neither mentioned Dr. He nor the weird coincidences.
Instead they celebrated.
When Leo kissed him that night, Sangwon didn't pull away. The distance between them vanished completely. They spent the night wrapped in each other's presence, exchanging soft words and unspoken promises, and discovering new reasons to stay close. For the first time in a long while, Sangwon allowed himself to stop thinking about experiments, grants, and expectations. Tonight, there was only Leo.
When morning finally arrived, still wrapped in Leo’s embrace, Sangwon realized with startling clarity that Leo had become as essential to his life as the work that mattered to him the most.
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One afternoon, while preparing archived records for an upcoming laboratory review, Sangwon found himself searching through storage cabinets that had not been opened in years.
Most of the material belonged to his mentor.
Doctor Jo had retired abruptly before his death, leaving behind decades of unfinished research and poorly organized documentation. Sangwon had inherited much of the work, but some records remained untouched, buried beneath forgotten proposals and obsolete datasets.
The discovery happened by accident.
A single folder, with dust coating its surface, had fallen behind a cabinet. The label was faded but was still readable—SUBJECT ALPHA.
At first, Sangwon assumed it referred to an animal trial but as he opened it, the photograph attached to the first page nearly made him drop the file. It was a younger version of himself, when he was still lab assistant Lee Sangwon.
For several seconds he simply stood there, unable to move and unable to breathe.
The folder contained hundreds of pages, from psychological evaluations to behavioral observations to reinforcement schedules.
Every page bore his mentor's signature and every page documented him.
Slowly, Sangwon sat down and began reading.
The research protocol felt disturbingly familiar: neural reinforcement pathways, attachment retention, reward dependency. The exact same principles that would later become the foundation of his own life's work…of his own research…of his own obsession.
And now he understood why out of all the PhD students, Doctor Jo had selected him. And it wasn’t because he was brilliant, or because he showed promise. It was because he was susceptible. The experiment had never relied on money, drugs, or physical coercion. The reward was validation…praise…recognition…approval.
Every achievement had been reinforced, every success was rewarded, and every accomplishment was celebrated until the pursuit itself became addictive. And because of it, research became inseparable from his own identity.
His mentor retired before drawing formal conclusions. But then, he never needed to, because the evidence was sitting in the laboratory reading his own case file.
Sangwon closed the folder with shaking hands. For the first time in his life, he questioned whether any of his choices had truly been his own. Or whether his career had been built on passion.
The answer should have horrified him. Instead, another thought surfaced—a worse one. Because hidden inside a locked drawer beside the cabinet was another collection of files. His own research files—the parts no one knew existed.
As he unlocked the first drawer, rows of folders waited inside. Each one labelled Subject 001, containing years of observations, years of experiment, and years of progress notes.
Subject 001: Lee Leo.
Years ago, before they met at a gallery, Sangwon first saw Leo sitting alone in a park, sketching strangers as they passed by. He noticed how intensely Leo observed people and how easily fixated he was when he found a subject to sketch.
And Sangwon became curious, and the curiosity became an interest, the interest became an experiment, and the experiment later turned into an opportunity.
Sangwon planned it all, from a casual shoulder bump on a crowded street to a slight smile when their eyes meet. Everything became carefully timed encounters, with subtle reinforcements that gradually became repeated exposures.
And then, he began seeing Leo everywhere he went. That’s how Sangwon knew his experiment had been a success. But Sangwon made a different discovery with Leo. In Leo's case, the most successful reinforcement wasn't praise. It was intimacy.
Every time Leo moved closer to him, the attachment deepened. Every reward strengthened the conditioning.
Sangwon knew what Leo was willing to do if he was expectant of a reward.
The first kiss came shortly after Dr. Kim resigned. Their relationship progressed and their bond intensified.
Then came Dr. He’s laboratory “accident”, of which Sangwon rewarded Leo with sex for the first time.
And Leo learned exactly what behavior produced the desired outcome. Sangwon never gave instructions or issued ordered. He simply mentioned problems then rewarded the solutions.
The office door opened. Leo stepped inside carrying two cups of coffee. For a moment neither of them spoke.
Leo's eyes lowered toward the participant file resting on the desk. Then he smiled.
"I had to bribe the security to let me in. I’ve missed you and I figured that you're working late again," Leo said softly.
Sangwon stared at him.
And for the first time since they met, he wasn't looking at his boyfriend. He wasn't seeing his soulmate. He was seeing something much worse.
He was seeing Subject 001, an experiment that had succeeded so completely it became too attached to its creator.