Archive of Our Own ^beta

Having Dazai Osamu as a mentor was… an experience, for sure. The man was simultaneously the most intelligent and brilliant person Atsushi had ever met, as well as an absolute menace. For all his clever plans and astute observations, Dazai had quite an awful work ethic and often used his mentee as a sort of scapegoat. On more than one occasion Atsushi found himself either doing the other man’s work or serving as a distraction to him while he procrastinated doing said work.

Right now, Atsushi suspected that he was doing both.

“Dazai-san… I’m not quite sure this is the way back to the agency,” he observed as they walked. He was hugging the case file to his chest, eyes darting around, taking in their surroundings. Meanwhile, Dazai strode with a lazy gait, hands clasped behind his back. Supposedly, they were to be making their way back to the agency after closing a case, but Atsushi was beginning to think that Dazai was prolonging their journey to avoid having to do more work.

“Are you questioning my genius, dear pupil?” the man inquired playfully, to which the pupil in question gave him an unimpressed look akin to that of a recently bathed cat. “Of course this isn’t the right way!” 

In response, Atsushi groaned, “Kunikida-san is gonna be so annoyed,” with a dramatic sigh, all of which seemed to amuse Dazai greatly. 

“But we’ve got something important to do,” Dazai informed with a suddenly grave tone, effectively bringing in Atsushi’s focused attention.

“What? What is it?”

The man’s gaze drifted to their destination: a street corner. 

“Three… two… one…” he muttered underneath his breath, before a triumphant smile stretched across his lips. “My predictions always come true.”

Atsushi followed his gaze, landing on a certain petite mafioso waiting at the corner to cross the street. His brows furrowed as he glanced back at a grinning Dazai.

“That’s Chuuya-san,” he observed. “Is this something to do with the mafia? Don’t we have a truce with them right now?” A beat. “Or— or do we have to work with him for something? I didn’t know that—”

“Our mission,” Dazai interrupted, tone still low and serious, “is to annoy the slug.” 

Atsushi fixed him with an unimpressed look once again. 

“You can go ahead and do that,” he said blandly, “but I’d rather not be on the receiving end of Kunikida-san’s wrath, so I’m just gonna—” he tried to turn and walk away, but his mentor grabbed him by the back of the collar of his shirt, preventing him from making his escape. 

“No, no, I need you for this,” he insisted, earning a sigh from the other, who knew there was no avoiding getting wrapped up in Dazai’s antics. 

“How’d you even find him here? It seems like he’s just trying to—” 

“You’re going to approach him and tell him that you’ve been assigned on a mission with him.”

“But I’m not!” he protested adamantly. “Why don’t you do it if you’re so hell-bent on this, Dazai-san?” 

“Because he won’t believe it if it’s coming from me,” he stated matter-of-factly, having the audacity to even sound a little annoyed. 

“Yeah, I wonder why that is,” Atsushi remarked sarcastically with a raised brow, their case file tucked under one arm, the hand of his other propped on his hip. “Look, I’m not going to get in the middle of your feud with Chuuya-san, ‘cause believe it or not, I don’t want to piss off an insanely powerful mafia executive—” 

“That is not how you feel about Akutagawa,” Dazai deadpanned.

“Akutagawa’s different, okay?” he replied, slightly exasperated. 

“You really should think to tell your subordinates exactly what you’re scheming before dragging them into your mess, shitty Dazai.” 

Both men turned to look at the Port Mafia executive regarding them with a sharp glare and a frown. Atsushi raised a hand and waved at him, clearly intimidated by the man even though he was inches shorter than him. Dazai did the same, but it was certainly not out of any respect or fear, waggling his fingers playfully, a brilliantly fake smile of innocence forming on his lips. 

“Hi, Chuuya-san,” Atsushi squeaked sheepishly, immediately followed by Dazai’s “Hey Chuuuuuuya!” 

“Keep the poor kid out of your bullshit, would ya?” Chuuya barked at Dazai, crossing his arms haughtily. The latter gasped dramatically at such a ridiculous notion.

“Atsushi, you don’t think I’m dragging—” a tired Atsushi seized his opportunity to interrupt mis mentor this time. 

“Yes, you are,” he said, and Chuuya snorted at this. 

“Lazy piece of shit, if you’re gonna try to mess with me, do it yourself!” Chuuya chastised, jabbing a finger into Dazai’s chest. 

“Aw, it sounds like Chuuya’s quite obsessed with me!” he teased brightly, crouching and putting his hands on his knees, addressing the short man like a child. “Is there something you wish to tell me, chibi?”

“Don’t fucking call me that, mackerel!” he said, aiming a kick at Dazai’s legs. He dodged this blow, of course, but doing so caused him to straighten up with a little jump. 

“I’m sorry, I just can’t hear you from way up here! Do you hear something, Atsushi? Maybe a tiny little dog yapping?” His grin was infectious, causing the younger man to bite back a smirk as he watched the pair’s antics. Dazai turned his attention back to his partner, who was fuming. “You’re sure growling like a little mutt,” he teased in a lilting voice, moving to snatch the mafioso’s hat.

“I’m not your fucking dog, bastard!” Chuuya shouted, both his hands flying up to keep his hat firmly in place. 

Their spat was drawing the attention of civilians around them, and Atsushi began becoming more and more uncomfortable, his hand coming up behind his neck as he cautiously muttered about them making a scene. 

“See, Atsushi, this is what happens when you try to reason with someone with anger issues,” Dazai informed, though his gaze lingered on the ginger, evaluating his responses and reactions.

“I think this is what happens when you deliberately push someone’s buttons, actually,” Atsushi mumbled, then adding, even quieter, “and I thought you were bad with Kunikida-san.”

“Try dealing with this bastard for seven years and see how short your temper gets,” Chuuya complained to the other, jerking his thumb in Dazai’s direction. Unsure of how to react to being directly addressed by one of the most fearsome mafiosos in Yokohama, Atsushi just nodded and chuckled nervously. 

“Chibi,” Dazai whined, “don’t talk bad about me to my student!” But, of course, this only made Chuuya’s face light up with a devious smile as he continued voicing his grievances.

“Did you know that one time this bastard made a bet that if he beat me at an arcade game I would get to be his dog?” He inquired smugly, a large grin finding its way to his lips as he attempted to embarrass Dazai.

“That’s where that comes from?” Atsushi’s gaze shifted between the two men. Chuuya nodded, Dazai let out a light snort through his nostrils, making his move next. 

“Yeah, and you were stupid enough to accept it!” he said triumphantly, like he had just won their battle, the amused glint in his eye unmistakable as he watched Chuuya retaliate.

“I was fucking fifteen years old and competitive as hell, of course I accepted!” Chuuya shot back, hands on his hips as he glared at the taller man. 

“You’ve known each other that long?” Both the men snapped their gaze to the Atsushi, who looked genuinely surprised at learning this information. 

“This shithead really doesn’t tell you agency folks anything, huh?” Chuuya said finally, taking a step back from his partner. 

“We didn’t even know he used to be mafia until a few months ago,” Atsushi revealed, to which the mafioso let out an unamused snort, folding his arms. Dazai took this opportunity to finally steal the ginger’s hat from right off his head, dangling it high so he couldn’t reach it.

And Atsushi never thought he’d see one of the most dangerous mafia executives use his insanely powerful ability to float up and grab the hat back, only to fall gracelessly back to the ground when he came in contact with No Longer Human, yet there he was.

-○-

“That was your plan all along?” Atsushi asked incredulously as he and Dazai made their way back to the agency. He’d had to practically drag Dazai away from Chuuya, the man having far too much fun annoying the living hell out of the poor mafioso. Then again, it went both ways, for Chuuya had no problem antagonizing Dazai, as well, gaining a similar type of sadistic glee from doing so. 

“Yep!” Dazai confirmed, popping the “p.” “I knew that you wouldn’t agree to messing with him, but if he just saw me approaching he would’ve avoided me one way or another. By making a scene and using my subordinate as bait, he engaged in conversation with us and so I got to bother him! Just being in my presence ruins his day, you know.” Atsushi stared at his mentor with some mix of disbelief and amazement, tilting his head slightly as he regarded the man, as if the longer he stared at him, the more sense he would make. 

His befuddlement was warranted, he thought. Atsushi had never actually seen Dazai and Chuuya interact directly for an extended amount of time. Sure, he had heard of their dynamic in passing around the office when Dazai complained about him, but before today he had never really seen Double Black in all their glory.

“You went through all of that… just so you could talk to him?” Atsushi questioned carefully, still regarding Dazai with the same expression scrunching up his young features. 

“To annoy him,” Dazai corrected enthusiastically, walking with a bit of a spring in his step, forcing Atsushi to keep up with his jovial pace. 

“I swear you two bicker like a married couple,” he grumbled, scrubbing a hand over his face with his free hand, the other still occupied with the file of the case they had been returning from before their run-in with the mafioso. It took him a moment to realize that Dazai had stopped in his tracks. “What?” he questioned as he turned to look at his mentor. The man was holding in laughter. 

“A married couple?” he questioned with amusement, failing to hold back his giggling. “You think we’re like a married couple?” It was then that he doubled over in laughter, clutching his stomach as he chortled. 

When he finally calmed enough to glance up again, he found Atsushi staring at him with a whole new type of astonishment on his face. 

“Dazai-san… that wasn’t supposed to be a joke…” he said to the detective, who simply shook his head at him, straightening up once more. 

“Atsushi, you fail to remember that married couples actually like each other,” he informed, ruffling silver hair as he passed Atsushi, beginning to walk again. 

“I— I mean, they don’t like each other all the time, sometimes they’re sick of each other!” Atsushi tried as he caught up with Dazai again. “But at the end of the day they’re there for each other, they have each other’s backs.” There was a beat of silence before he spoke again, a little sheepish, “Isn’t that how you are with Chuuya-san?”

“Nope!” Dazai replied cheerfully, though the reply was a little bit quicker than it should have been, as if the words forced themselves past Dazai’s lips in a rush. 

“Weren’t… you two partners, though?” Atsushi inquired hesitantly, timidly pushing the subject further. He didn’t watch the pair engage in playful banter for twenty minutes straight for Dazai to tell him the mafioso meant nothing to him.. 

“Yep!” came another short response. 

“I— okay.” Unsatisfied, he settled with the clipped answers, taking the hint not to ask anything more. Dazai walked along, his usual chipper self — actually, he seemed even more cheerful than before, somehow. 

Atsushi didn’t pretend to fully understand his mentor, he would be stupid to do so, because Dazai Osamu hid his true reactions under layers and layers of fabric, secrets tucked beneath the sterile white of his bandages. If there was one thing he did pride himself on, though, it was sometimes being able to tell when Dazai was wrapping himself up further, adding on another layer of deception to cover up whatever truth was attempting to bleed through.

Atsushi was certain Dazai’s cheerful attitude being amplified was just that: a cover-up of his true feelings. 

So while Atsushi wasn’t going to push the subject any further, he had a suspicion that his assumptions were more true than Dazai was willing to admit. 

Well, for now, at least.

-○-

“Atsushiiiiiiii!” Dazai called from across the office. He was dramatically draped over the couch, head hanging upside down over the armrest, as his subordinate filed his paperwork.

“Yes, Dazai-san?” Atsushi asked with exasperation, turning at his desk to regard the man. 

“Could you hand me my phone? It’s over there, on my desk.”

His desk was approximately five feet away from the couch.

“Actually, I think you can do it yourself, Dazai-san. I believe in you,” Atsushi replied, straightening back up and turning back to his work.

“What? How cruel! My own student isn’t even listening to my orders!” he lamented loudly, causing Kunikida to throw him a glare and Ranpo to roll his eyes from behind his pile of snacks.

See, the issue was that if Atsushi continued to refuse Dazai’s request, it would only infuriate the rest of his co-workers more, especially Kunikida. So for the sake of maintaining the brittle office peace between the eccentric personalities that the agency seemed to attract, he relented. 

“Fine, fine!” Atsushi said, raising his hands in defeat and rising from his desk. It was only then that he noticed Dazai’s phone lighting up every ten seconds, and once he approached it, he noticed that there were nearly one hundred message notifications from “Slug”. 

He held back the urge to snort loudly. ‘Not like a married couple’ my ass.

“Just as I thought,” Dazai muttered upon receiving his phone. He let it drop to his chest.

“Chuuya-san, right?” he inquired innocently, though he didn’t doubt that his mentor saw him glancing at the notifications (Dazai didn’t miss anything).

“Unfortunately!” He sighed loudly and dramatically, and it was just too exaggerated for Atsushi to truly believe that he was properly bothered by the other man contacting him.

“Why don’t you answer? It’s only gonna get worse if you ignore it.” 

Dazai scoffed at the idea. “I haven’t answered any of chibi’s texts in over four years,” he stated simply. 

Atsushi blinked.“What?”

“This is my old phone, the one from back when I was in the Port Mafia,” he explained, and he patted around the inside of his vest until he produced another flip phone. “This one is the one I use now.” He held it up, and though the two phones were similar, it was clear that the second one was a newer model, lacking the clunkiness and weathering that the other sported. 

“They can’t track you through the old one?” Dazai shook his head at this with a soft smirk lighting up his features. “Then why bother keeping it?” His smile diminished at this second question, still there, but less bright. 

“To mess with Chuuya, obviously,” he settled on with a shrug. Atsushi narrowed his eyes at his mentor.

“Right,” he said slowly, “because that makes sense.” His sarcasm and disbelief were evident, but it did not appear to faze Dazai in the slightest, who continued to smirk innocently at Atsushi.

As he returned to his own desk, knowing he wasn’t going to get any further with this conversation, he wondered what that phone truly meant to Dazai. From his limited understanding of the other man’s past, he knew that he completely vanished when he defected from the mafia, which allowed him time to clear his ledger and eventually start anew with the agency. 

Why did Dazai bother to keep reading the messages from his former partner, even to this day?

It really wasn’t any of Atsushi’s business, and he really ought to not make these kinds of assumptions, especially because Dazai intentionally kept his past and emotions so close to his chest, but he couldn’t help but poke and prod sometimes. Maybe it had to do with being compelled to help people, or maybe he was just nosy, but something told him there was more to Dazai and Chuuya’s partnership than the former wanted to admit. Hell, he had watched Dazai actively seek out the mafioso just to bicker with him. That was hardly apathetic behavior. 

He glanced over again from his desk to see the other man biting back a smile from whatever message Chuuya had sent him. Perhaps it was a taunt? An angry insult? Dazai always seemed to derive this odd joy from irritating the mafioso. 

Atsushi just shook his head and busied himself with Dazai’s paperwork.

-○-

 “It’s not a prank this time, I swear.”

“Yeah, I know, kid.”

Atsushi had run into Port Mafia executive Nakahara Chuuya on his mission. Just his luck.

At first, he wasn’t wholly convinced the coincidence had nothing to do with Dazai, but the more he thought about it, the more he seriously doubted it. He figured that the man himself would surely be present if his objective was to annoy Chuuya. In fact, Kunikida was the one who had assigned Atsushi this mission to track an ability-using con artist, one of his first solo operations. Thus, Atsushi believed that it likely was a true coincidence that he came across the mafioso while investigating the abandoned apartment of the criminal.

Even so, it was still weird.

“As long as we’re going after the same target, would you want to work together on this?” the detective offered tentatively. The shorter man just shrugged in response, typing something on his phone before pocketing it. 

“Makes sense,” he replied simply. That was that, they were now temporarily allied. 

After they exchanged information, Chuuya took the lead, suggesting the next location to check out, which Atsushi appreciated. He had been intimidated by being given his own case. 

Though, he did question how he ended up with a case at the same level as something a mafia executive would tackle.

“I don’t get it,” he muttered to himself as he considered this fact, the logistics not adding up in his head. If Chuuya was so important and powerful, why assign him something that would likely be simple for him? Or, alternatively, why entrust Atsushi with a solo mission troublesome enough that a mafia executive was assigned the same thing?

“What don’t you get?” The mafioso asked, and much to Atsushi’s shame, he physically jolted at being caught thinking aloud by the other man. 

“Oh, I, um, I just—” he stammered before Chuuya cut him off. 

“Contrary to what you might hear from shitty Dazai, I’m not a dog, I don’t bite,” he informed bluntly, raising a brow at Atsushi’s blubbering.

“Right, I— sorry,” he sputtered, before continuing. “I was just kind of wondering how we, um— how we got assigned the same case? Considering the difference in our positions in our organizations, I mean.” Chuuya nodded at this, like he understood Atsushi’s confusion. 

He didn’t break stride as he offered his response, “Just because I’m an executive doesn’t mean that I don’t have to pull my weight,” he explained, “yes, this is a lower-level case, but due to the nature of the job, we only have so many capable members. Plus, this concerns the gem trade, which I used to work in. It made sense for me to take this case.” 

“Oh, that adds up, I guess,” a beat, he considered whether or not he should bring this up, but…. “When I got this assignment, Dazai-san gave me some advice since he apparently used to work in the gem trade, as well. Did you guys… work together?” Chuuya’s jaw clenched and his eyes narrowed at this, and the agency member worried he made a mistake by bringing up Dazai.

“You could say that,” he replied somewhat bitterly, folding his arms. When Atsushi only gave him a puzzled look, he let out a short sigh and clarified, “That bastard rose through the ranks quicker than I did, so even after completing the same amount of jobs, he was overseeing and setting up my work in the gem trade. We were partners in the field, but it was different when it came to the mafia’s hierarchy.”

“Oh, so you were in competition with him, then?” Atsushi pointed out, the most logical explanation to him. It would explain some of the pair’s animosity despite having been previously partners, at least.   

“Yeah,” he confirmed with a light snort, “he was always ahead, though. Then he threw it all away.” The remark was accompanied by an eye roll from Chuuya and the tightening of his grip on his folded arms. 

“So you’re glad to have him gone?”

“Yeah,” the response came automatic and quick, like it was instinctual, trained (surely there’s a joke about a dog in there somewhere, but Dazai wasn’t there to make it). “I mean, he’s a fucking traitor and made things complicated as hell for everyone, of course I’m glad I don’t have to deal with his annoying ass every day.”

“Now I have to instead,” Atsushi joked, earning a surprised chuckle from the mafioso at his side. Suddenly, he was unsure if he should’ve insulted his own mentor.. But then again, surely Chuuya understood what it was like to work with the bandaged menace. Still, he felt the need to amend his statement, “I— I mean, don’t get me wrong, I admire him, but—”

“But he’s a fucking pain in the ass,” the mafioso finished for him. 

“I might not have phrased it that way, but… yeah, sometimes.” This earned a smirk from Chuuya, who shook his head in a way that Atsushi thought might denote fondness?

“I truly pity anyone who has the displeasure of knowing that bastard,” Chuuya grumbled, though he was still smiling slightly as he did. 

“Well, I mean, he’s not that bad,” Atsushi offered, feeling the need to defend his mentor, if ever so slightly. “Despite his, uh, meddling, he’s the best there is when it really counts. And— and he’s helped me a lot. Personally, I mean.” At the end of his little spiel he didn’t really know how to evaluate the expression the mafioso was giving him, somewhere between doubtfulness and intrigue. 

“You know that Akutagawa was under his mentorship for a while, right?” the ginger inquired after a beat of silence. Atsushi nodded. Though he didn’t understand the details, Akutagawa had mentioned it himself, and it appeared to be the root of his obsession with gaining the bandaged man’s approval. “He treats you differently. He’s changed since he left the mafia.” Chuuya spoke to Atsushi, but it also seemed as if he was speaking to himself, something a bit more introspective. 

“How is he different, exactly?” Curiosity got the better of him and the question tumbled past his lips before he got the chance to think it through. Atsushi restrained himself from physically slapping a hand over his mouth. Why the hell was he having this deep conversation with a mafia executive, anyway?

“You’re not homicidal, for one,” Chuuya informed dryly, and then, a little quieter, “he seems less… miserable than he used to.” 

“He’s still, uh...” Atsushi paused, brows furrowed. “He still wants to…” he trailed off again, though, unsure how to put it delicately. This was Dazai’s former partner, after all.

“I know,” the mafioso finally said with a sigh, but not one of exasperation. It was a bit heavier, perhaps more tired.

“I hope he never… succeeds,” Atsushi muttered, wincing physically when he realized who he was saying this to. When he turned to look at the person in question, he found Chuuya regarding him with a pensive expression. He pressed his lips together before speaking again.

“I like to think his attempts don’t fail by coincidence,” he offered, and Atsushi took this information and cradled it gently in his hands, nodding slightly. 

The rest of their walk was slightly awkward, the heaviness of their oddly vulnerable conversation weighing down the air and creating an odd tension as they made their way to the location. Once there, it broke as they threw themselves into their work. 

Chuuya found evidence of the smuggler having been in the location that Atsushi would have otherwise missed, and he was secretly thankful he’d run into the mafioso. Sure, the man was kind of intimidating, but through their conversation and collaborative work, he learned that Chuuya wasn’t quite as scary a person as one might believe. He was less explosive when not being provoked by Dazai, and though he was known for his powerful combative ability, he was quite intelligent and thorough, as well. He was well-rounded, which made sense given that the man was an executive. By the time they tracked down the con artist and beat the shit out of him and his lackeys, he had gained a healthy respect for the petite mafioso. 

“Thanks for working with me,” Atsushi said quietly after everything was wrapped up, and Chuuya snorted lightly at him. 

“Look, we might be on opposing sides, but I know when it’s useful to cooperate with you agency bastards,” he said, and though it should have felt insulting, Atsushi felt like there was some genuine kindness in the statement. “You’re much more tolerable than shitty Dazai, at least,” he tacked on, which brought a smile to Atsushi’s face. 

“Aw, chibi is being so mean!” A voice rang out behind them, and immediately Atsushi watched as the mafioso frowned and huffed, turning in the direction of the voice. 

“What the hell are you doing here, you shitty-ass bastard?” he barked at Dazai, who stood innocently on the sidewalk, hands clasped behind his back as he flashed a grin at the unlikely pair. 

“Why, I’ve just come to retrieve my student!” Atsushi sighed at this, for he was entirely capable of making his way back to the agency on his own. His best guess is that after he told Kunikida he decided to collaborate with Chuuya on the case, Dazai caught wind and decided to involve himself. 

To annoy Chuuya, of course. 

And Atsushi was made to watch as the men bickered with each other quite loudly once again , and he could almost picture the two as teens acting the same exact way. That sense of competition they had apparently seemed to have never faded away entirely. And it was this, plus the general knowledge that he had gained about the pair’s relationship recently, that made him come to the conclusion that Dazai often looked like he was having the most fun when he was chastising Chuuya. 

He wasn’t quite sure what this meant in terms of what their relationship was, and he knew it really wasn’t his business in the first place, but it did feel odd to have seen some of what seeped through those sterile bandages his mentor wrapped himself up in. 

Chuuya made him bleed emotion to a greater extent than most.

The conversation Atsushi had with the mafioso put this all in perspective: they knew each other well, and both cared a little more than they let on. Whether this meant that they were closer friends than they’d admit or that there was something more… Atsushi wasn’t going to attempt to decipher.

But then, as he watched the pair trade insults and taunts, he saw how Chuuya tugged Dazai down to his eye level by his bolo tie. He saw how Dazai’s expression flickered for the slightest moment, so quick that Atsushi might have missed it had he blinked. He saw how Chuuya smirked at the reaction, and how Dazai shot a competitive grin right back at his partner.

“Try me, bastard,” Chuuya challenged brashly, brows furrowed despite his cocky grin. 

“You wish,” Dazai shot back, mirroring the other’s expression.

Yeah. There was definitely something more .