Nakahara Chuuya couldn’t remember a time when Dazai Osamu wasn’t a thorn in his side.

They met in their first year of med school, during anatomy lab of all things—Dazai walked in late, looking like he hadn’t slept in days, wearing a half-buttoned white coat over a black turtleneck and dress pants like he was auditioning for a funeral. He strolled past everyone and plopped down beside Chuuya with a sigh, announcing, “Guess we’re stuck cutting up dead people together, shortie.”

That set the tone for everything that followed.

Chuuya hated him immediately.

Yet somehow, from that day on, they were always paired together—by fate, or some twisted joke by the professor, Chuuya didn’t know. What he did know was that Dazai never shut up. He had a theory for everything, a smug smile begging to be punched, and a way of answering questions with more questions that made Chuuya’s blood boil. He was annoyingly good at everything he didn’t try at, and infuriatingly lazy about everything he should try at.

They argued constantly—about treatments, diagnoses, ethics, sleep, lunch, coffee, blood types. Chuuya once nearly threw a scalpel across the lab because Dazai insisted that “technically” spleens weren’t that important. They got kicked out of class discussions more times than Chuuya could count, but Dazai never stopped poking, provoking, pushing every single one of his buttons.

It wasn’t just about irritation. Not really.

Because Dazai also had the kind of brilliance that couldn’t be ignored. Chuuya had always been top of his class—disciplined, sharp, focused—but Dazai was chaos and genius rolled into one. He skipped readings and still aced exams. He barely listened and still asked the one question the professor couldn’t answer. As much as Chuuya hated it, he started to expect that voice behind him, dropping sarcasm or challenging him with a smug, “Wanna bet on that, Chuuya?”

They weren’t friends. God, no.

They were rivals.

Reluctant partners. Constant competitors. Fire and wind—violent, unpredictable, always colliding.

Still, somewhere between the bickering and the backhanded compliments, between stolen notes and cafeteria coffee at 2 a.m., Chuuya started to notice things.

Like how Dazai would slow down when Chuuya limped from a sprain. How he’d drop painkillers on Chuuya’s desk without a word. How he never said anything when Chuuya cried after losing their first patient—just handed him a drink and made a dumb joke about ghosts not haunting redheads.

Beneath the arrogance and chaos, Dazai cared—quietly, secretly. Chuuya saw it in the way he held a child’s hand in the ER, or how he memorized med interactions like lives depended on it. Like he had to keep everyone breathing because he knew what it meant to lose.

Chuuya didn’t know when their rivalry stopped being just rivalry.

It was still there, of course. The arguing hadn’t stopped. Neither had the competition. But sometimes, when their shoulders brushed over the same case file, or when Dazai murmured his thoughts like he needed Chuuya to hear them first, or when Chuuya caught himself waiting for Dazai’s reaction before deciding—he wondered if there was something more.

He’d never say it. Dazai would never let him live it down.

But in the quiet moments, when hospital lights flickered and the halls echoed with tired footsteps, Chuuya let himself admit: Dazai made him sharper. Smarter. Better.

Even if he was the most annoying bastard alive.

Because rivalry, at its core, was just another kind of intimacy. And maybe—just maybe—Chuuya didn’t mind being seen so clearly, if it was by Dazai.