Chapter Text
The conference room was quiet in the way rooms only were when enemies were forced to sit across from each other.
On one side, the Armed Detective Agency.
On the other, the Port Mafia.
At the head of the table, strategy maps were spread out between them.
And seated across from each other—
Osamu Dazai and Chuuya Nakahara.
They weren’t touching.
They weren’t even standing close.
If anything, they looked perfectly professional.
“Your organization will take the east corridor,” Chuuya said evenly, gloved hands resting on the table.
Dazai didn’t look at the map.
He looked at Chuuya.
“Mm. That’s fine,” he said lazily. “You’ll handle the explosives, then.”
Chuuya didn’t nod.
Didn’t confirm.
He just held Dazai’s gaze for half a second.
And somehow—
Agreement passed between them.
Atsushi frowned.
“…Wait, we didn’t go over that part yet.”
“We don’t need to,” Dazai replied lightly.
Chuuya’s lips twitched — barely. “Try to keep up.”
Ranpo, who had been chewing idly on a snack, paused.
His eyes opened.
Fully.
Interesting.
The rest of the meeting continued normally. Plans. Assignments. Timelines.
But every time someone suggested an adjustment, Dazai’s eyes flicked to Chuuya first.
Not for permission.
Not for approval.
For alignment.
And Chuuya always answered before anyone else could.
Like they’d already discussed it.
Like they already knew.
Akutagawa noticed too.
His gaze sharpened.
“They are coordinating without speaking,” he said flatly.
“That’s called experience,” Chuuya replied.
Dazai smiled.
Ranpo leaned back in his chair.
“No,” he murmured, almost to himself. “That’s called something else.”
Across the table, Dazai and Chuuya didn’t react.
But their eyes met again.
And this time—
There was something in it.
Not rivalry.
Not annoyance.
Something steadier.
Something practiced.
Something familiar.
Ranpo grinned.
Oh.
Oh, this was going to be fun .
————————————
The alley smelled of damp concrete and smoke. Dazai crouched behind a stack of crates, surveying the area with a lazy tilt of his head. Chuuya moved beside him, stance precise, hands clenched, ready for action.
“Careful,” Dazai murmured, leaning slightly closer. “Don’t get your outfit dirty. I don’t want to be the one washing it later.”
Chuuya’s jaw ticked. “Hmph. You’re the one who’s going to get covered in soot first.”
Neither of them realized how loud their conversation carried through the earpieces everyone else was wearing.
“…Did he just say he’s going to wash Chuuya’s clothes?” Ranpo whispered, barely containing a laugh.
Atsushi froze, heart thudding. “…Wait… what?”
Chuuya’s eyes narrowed at Dazai. “Don’t think I didn’t hear that.”
“Hmm?” Dazai hummed, tilting his head innocently. “Hear what?”
Ranpo’s grin widened. “Ohhh… now it all makes sense.”
Dazai stepped lightly to peek around the corner. “You’ve got the left flank. I’ll cover the right.”
“Don’t slow me down,” Chuuya snapped. “I’m faster than you.”
“Faster, maybe,” Dazai said softly, almost teasingly, “but clumsy as ever.”
“…Clumsy?!” Chuuya barked, and his voice echoed slightly through the comms.
Atsushi’s cheeks burned. “They… they sound like they hate each other,” he whispered. “But also… not?”
“Not exactly,” Ranpo muttered, chewing on the end of his pen. “It’s… familiarity. Like old married couples.”
Akutagawa’s jaw tightened. “…That’s terrifying.”
Kunikida groaned quietly into his mic. “Focus on the mission, please.”
Meanwhile, Dazai and Chuuya moved in perfect synchronization. Not because anyone could see it, but because they knew each other’s rhythms.
A small crate toppled nearby.
“Careful!” Dazai hissed, eyes darting. “Don’t trip.”
Chuuya’s exhale was sharp. “…I didn’t.”
“But you almost did.” Dazai’s tone was teasing. “I’d have to carry you back after the mission. Again.”
“…You think I need your help?” Chuuya muttered, voice low but clipped.
“Depends,” Dazai said casually, “if you want your suit intact, then yes.”
The earpieces crackled. Ranpo’s chuckle leaked through. “I am not imagining this.”
Atsushi squeaked. “…They’re… married?”
Kunikida pinched the bridge of his nose. “This is highly unprofessional!”
Chuuya growled at Dazai, though his tone was more amused than angry. “…You’re going to get us in trouble.”
Dazai hummed softly. “You love it.”
Chuuya rolled his eyes but didn’t deny it.
They reached the rendezvous point, mission objective complete. Not a single shot fired in their immediate vicinity, not a single misstep. Yet the tension in the earpieces told a different story.
Mori’s voice cut through calmly, but with a smirk that only some could hear: “Ah. So Double Black is still very much… effective.”
Fukuzawa’s calm voice followed. “Their coordination is precise. Almost unnervingly so.”
Chuuya and Dazai removed their earpieces. Chuuya’s glare could have burned holes through the wall. Dazai, of course, was grinning.
“Why did you have to let them hear that?” Chuuya muttered.
Dazai leaned back, hands behind his head, eyes sparkling. “Hear what?”
“You know…” Chuuya growled. “…the outfit comment.”
“I was being helpful,” Dazai said innocently. “And maybe a little entertaining.”
From the observation point, Ranpo leaned back and laughed softly. “They’re married. Ohhh… I knew it.”
Atsushi, still blushing, whispered: “So… they really are married?”
Akutagawa scowled. “…I can’t believe I’m witnessing this.”
Kunikida groaned audibly. “I officially give up. Focus on mission next time, not… domestic squabbles!”
Chuuya crossed his arms and muttered, “You’re impossible.”
Dazai hummed. “…And yet you love me.”
Chuuya’s jaw twitched. “…Shut up.”
Somewhere, Mori’s smirk widened. Fukuzawa simply nodded, noting how dangerously effective their “married” coordination could be.
And so, the mission had gone perfectly.
But the real operation — everyone realizing the depth of Double Black’s bond — had only just begun.
The warehouse smelled of rust and damp, a perfect place for an ambush. Dazai crouched low behind a stack of crates, eyes scanning the shadowy interior, while Chuuya moved beside him, crouched and tense.
“Stay close,” Dazai murmured, leaning just enough so his shoulder brushed Chuuya’s. “I don’t want to lose you in the dark.”
Chuuya shot him a sharp look, but his hand subtly rested against the wall near Dazai, steadying himself. “As if you could keep up with me,” he muttered.
A faint laugh echoed in the earpieces. Ranpo’s voice was almost gleeful. “Ohhh… everyone can hear this.”
Atsushi’s whisper came next. “…They sound… like they live together or something?”
Dazai tilted his head, eyes flicking to Chuuya. “Careful with that crate,” he whispered. “I’d hate to be the one cleaning up after you.”
Chuuya’s elbow nudged Dazai lightly, and he nearly fell over. “You’ll get yourself dirty first, idiot.”
The first wave of enemies came rushing down the hall. Chuuya threw himself into the fight, dodging and weaving with precision. Dazai was right behind him, knocking attackers off balance with his cane and throwing knives, moving like a shadow.
One of the guards tried to grab Chuuya from behind. Dazai spun, shoving the man aside and yanking Chuuya out of reach. They stumbled together, and Dazai’s arm went around Chuuya’s shoulders to steady him.
“Watch yourself!” Dazai teased, voice low.
“I am watching myself!” Chuuya snapped, but his grip on Dazai’s wrist lingered just a fraction longer than necessary.
Ranpo muttered into his mic: “Yeah… that is definitely not just professional.”
Atsushi froze. “…Wait… he just caught him?”
Chuuya growled, shoving Dazai lightly. “Don’t start acting like you saved me.”
Dazai smirked, brushing dust off his sleeve with one hand while his other stayed near Chuuya’s arm. “Hmm… I didn’t save you. I just… made sure you didn’t ruin your suit.”
Chuuya’s jaw ticked, but a faint smile tugged at his lips. “…You’re impossible.”
The next wave came from the side, and they moved without a word. Dazai flicked his wrist, tossing a knife; Chuuya slid under the line of attack and kicked another enemy off balance. When Chuuya slipped slightly on the wet floor, Dazai caught his elbow and yanked him upright.
“You’re heavy,” Chuuya muttered, but didn’t pull away.
“And you’re stubborn,” Dazai shot back, voice low. “Balance that out, and we’re perfect.”
Kunikida’s earpiece crackled. “Focus, both of you!”
“Can’t!” Chuuya hissed, throwing a punch while glancing at Dazai. “He’s distracting me!”
Dazai hummed in mock offense. “…Am I now?”
The fight ended quickly. Double Black stood side by side, breathing hard, dust on their sleeves, hair tousled. Dazai leaned slightly against Chuuya, wiping his face with the back of his hand.
“Good teamwork,” Dazai murmured.
Chuuya’s hand rested on Dazai’s shoulder briefly before he pushed him upright. “…You’re lucky I like you,” he muttered.
Dazai smirked, brushing off the comment. “…Yeah, I know.”
Ranpo’s voice came through the comms, loud and gleeful. “OHHHHHH. That explains EVERYTHING.”
Atsushi’s whisper: “…Wait… are they married??”
Akutagawa growled silently. “…I hate this.”
Kunikida groaned audibly. “…Unbelievable.”
Chuuya shot Dazai a glare, but the corner of his lips twitched. “You let them hear that, didn’t you?”
“I might have,” Dazai admitted lazily, leaning closer again. “…But look at their faces. Totally worth it.”
Chuuya groaned, but allowed Dazai to hook an arm around his shoulder as they walked back to the rendezvous point, their steps perfectly in sync.
The mission was over. The enemy neutralized.
But the real chaos—the knowledge of Double Black’s married life—had just begun