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English
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Published:
2025-10-06
Updated:
2026-02-23
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13,670
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6/10
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You could let it all go

Summary:

Both of their fates are sealed: one will sit on the throne of crimes, the other will tear it down. They shouldn't have met at sixteen, shouldn't have formed something resembling a friendship, shouldn't have found more similarities than differences. The heir of a crime lord and the son of a detective walk into a bar — sounds like the start of a bad joke.

(AKA Kunizai au where they grow up together from teens, with found family because Odasaku. Please read the first note!! Thank you<3)

Notes:

Hi! This is my first fic here, and I’m partially writing it to practice English, as it’s not my first language, so I’m sorry for any mistakes!
Please note that although this is technically not an AU, I don’t necessarily follow canon either, and I took inspiration from the irl author’s literature (for example, Dazai’s past will be based on Yozo from NLH).
Updates every Monday if university doesn’t take all my will to live. Hope you’ll enjoy it <33
(Titles from “It’s Called: Freefall” by Rainbow Kitten Surprise, which is about as cheerful as it sounds, heavily recommend it to everyone)

Chapter 1: Called to the Devil and the Devil did come

Chapter Text

“Is there really any value to this thing we call living?”

Full legal name: Dazai Osamu

Birth name: —

Current age: (15) 16

Height: 166 cm

Weight: 40 kg

Mother: —

Father: —

Legal guardian: Mori Ougai

At least fifteen other traits were listed, including the exact date and place of his birth, blood type, and diagnoses. But he didn’t read any further. That one bothered him too much. Mori Ougai was his legal guardian, and no force on earth could change that. He knew that children with awful parents and guardians typically can’t wait to reach the age of maturity, because once they do, they don’t have to suffer by their hands anymore. But that wasn’t the case for him. Even if Mori does lose some power over him once he turns 20, the mafia won’t.

He will never be free.

The office was dark as always. Minimal lighting, dark furniture, closed curtains. Dazai felt comfortable in the darkness; in a weird way, it felt like home. The huge black coat draped over his shoulders made him appear like one of the shadows, like an animal choosing its pattern carefully to match the colors of the forest. Darkness was easy. Darkness was safe. Darkness was what he always knew.

His dark eye blinked slowly like that of a cat, as he observed the paper in his hands. Then, with a disgusted face, the put his file back to where he found it, in a drawer that was easier to pick than Mori probably thought. He knew the boss didn’t want him to snoop around in his office, but he couldn’t care less. That bastard took longer to get here than he promised.

His sensitive ears picked up on the sound of approaching footsteps. It was Mori, he could tell by the speed, heaviness, and rhythm. He neatly folded his hands in front of him, and started focusing on lowering his heartbeat to a normal rate. He wasn’t scared of Mori, no, that wasn’t the correct world. But there was an uneasy feeling in his stomach. Disgust? No…

“Dazai… oh, you’re already here?” the man asked as he entered the office. As if he didn’t send someone to get him over half an hour ago. “I didn’t want to keep you waiting, but I’m just so busy lately. That’s the life of a man of high position.”

“I can imagine,” Dazai said, glancing to the side. His eye landed on the boss’ chair. He plopped down with a small smirk on his face, with his arms on the armrests and legs spreaded wide, as if he was right at home.

“Good to see you practicing for your future career,” said Mori, as he closed the door and stepped closer.

“You don’t want me to. For me to sit here, you’ll have to be dead.”

Mori’s cheerful expression immediately changed to a slightly annoyed one, which made Dazai’s grin grow wider. He put his feet up on the desk, which forced him to lean further back in the chair. Even though he was much lighter than Mori, the old piece of furniture still creaked under his weight.

“Such a brat,” Mori murmured under his breath, then continued with a louder and more serious tone, “I have a job for you, and it won’t be pretty.”

“What a surprise. I suppose you want me to involve Chuuya as well?”

“It won’t be necessary. This isn’t a hard gig, the only reason I ask you to do it is because it’s very confidential.”

“One of these days I’ll stop keeping my mouth shut for you.”

“If you know what’s good for you, that day won’t come anytime soon.”

“You should know better than to trust the self-preservation instinct of a suicidal person. Maybe the years are finally catching up to you.”

Mori calmly closed his eyes. “I suppose you’re right. It would be more effective if you had to worry about what’s good for Oda Sakunosuke.”

It was Dazai’s turn to drop his smile. He felt his heart skip a beat, and a heavy feeling clouded his mind, like thick fog. His right leg stopped bouncing; he didn’t even realise it started. However, he didn’t show any of this. He didn’t allow himself to. As soon as he felt his smile fade, he immediately replaced the previous cheerful expression with an innocently confused one.

“What do you mean? Isn’t that the name of someone in the lower ranks?” he asked, even tilting his head to the side.

“A little birdie told me that you’re pretty good friends. Even calling him Odasaku like a child? Somehow you can still surprise me. A rather unpleasant surprise, but still.” He looked at Dazai’s expression through half-lidded eyes, and a sly smile appeared on his lips. “It would be a shame if something happened to him. And I would be a bad guardian if I didn’t teach you responsibility.”

He started circling the desk, with his hands behind his back. Dazai got up and followed him, so they ended up on opposite sides of the desk again. Mori sat down much more gracefully than Dazai did, and leaned forward with his elbows on the desk, fingers woven together.

“You’re an executive, Dazai. And, more importantly, my heir. If you get involved with people like him, they won’t take you as seriously as they should.”

“As I said,” Dazai started, placing emphasis on the last word, “we aren’t friends or anything. I only know him because he worked under me a few times. That little birdie was either dumb or a liar.”

“That’s good to hear. For a moment I thought you forgot your priorities.”

Dazai stayed quiet.

Mori reached down with a key to unlock one of the drawers, when he noticed that it’s already open. He looked up at Dazai, whose smile slowly crawled back on his childish face.

“What did I tell you about snooping?”

“I only read my file, don’t worry. I already knew everything that’s in it.”

“Still… you don’t want to be punished.”

He pulled out a few papers from under the file, and handed them to Dazai. After the boy quickly read through it, he immediately understood why was he the only one who could be trusted with it. He sighted dramatically as he handed them back.

“Have you memorized it?”

“Yes. And you’re an asshole.”

Mori smiled. “Aren’t we all down here?”

Dazai turned to leave the office, with an elegant little swirl of his long coat. But he stopped in front of the door, as he still had one question. “By the way, why did you put my file into the drawer of your desk? It’s a bit unsafe.”

“If you really have to know, I’m working on it. Adding a few details, correcting mistakes. We’re going to do a checkup soon.”

“I won’t be available this Saturday,” Dazai stated calmly, as if he was scheduling an actual appointment with a doctor.

“Oh? What’s more important?”

Dazai turned towards him slightly, but from his blind side. This way he didn’t have to see Mori, but the man could see that he’s smiling. “I’m going to a charity event.”

Mori let out a surprised sound, then a sharp laugh. “Fine, you don’t have to tell me if you really don’t want to. Finish this job and then you’re free until next Monday.”

When Dazai left the office, he made sure to close the door properly. He considered leaving it open on purpose, just to annoy Mori, but he quickly realised that closing it as fast as possible is more insulting, since it shows that he doesn’t want to see his face.

The mafia members on the corridor immediately became silent. They always did when he was there. Mori called this respect — mixed with fear. They wanted to be ready for any orders he may give. But Dazai didn’t need them at the moment, so he just walked down the corridor between them. They bowed their heads like blades of grass under a cold breeze.

Now, Dazai was an amazing liar. But he didn’t want to waste energy on lying, when he knew that Mori wouldn’t believe the truth anyway. As impossible as it may sound, the Demon Prodigy was indeed about to go to a charity event. Odasaku dragged him into it, he tried to play the “for the kids” card, but honestly, Dazai didn’t mind doing it for him either. He just needed some normal clothes, but Odasaku promised to lend him some.

However, he had to finish that job first.

--------

“If you try to save someone you can’t save, you’ll both end up sinking.”

Full legal name: Kunikida Doppo

Birth name: Kunikida Doppo

Current age: 16

Height: 170 cm

Weight: 62 kg

Mother: [deceased]

Father: [deceased]

Legal guardian: Fukuzawa Yukichi

About ten other traits were listed on the paper. The blond boy read through all of them carefully, checking if they’re correct. He couldn’t find any mistakes, everything seemed to be alright. He handed the paper back to the man sitting at the desk in front of him, who looked up, and took them with a small nod.

Early afternoon light warmed the office. They didn’t even need artificial lighting, other than a small desk lamp pointed at the paperwork in front of the older man. The sunrays reflected off the boy’s glasses, but his greenish eyes shone brighter.

“Everything is correct,” the boy stated. He tried to hide his excitement, as he liked to appear mature and serious. But it didn’t really work. His sweaty hands were fidgeting with his knitted vest. “So, when can I start?”

“Be more patient, Kunikida,” Fukuzawa said, putting the paper away. “We still have a few more formats to fill out, then we’ll have to test your abilities.” When he noticed that Kunikida wants to argue or complain, he put a hand up to signal that he didn’t finish yet. “It will only take a few days, and I promise you can start working next week.”

Kunikida seemed to understand it, and when he spoke again, he did so with a calmer voice. “Alright. I’m sorry, it’s just really important to me. I love your agency, and when you told me that I can get a part-time job here while I’m still in school, I got really excited.”

Fukuzawa smiled warmly. “I’m glad you like the Agency so much. I promise to give you a full-time position as soon as you’re done with your studies.”

Kunikida’s face lit up. Ever since he was adopted by Fukuzawa, he always admired the man. He was strong, wise, and everything Kunikida ever wanted to be. A true role model.

“Thank you! I’ll do my best!”

“I’m sure you will, you always do. I’m… really proud of you, Kunikida.”

The boy’s excited smile eased into a proud and emotional one. That was the biggest compliment he could ever get.

Fukuzawa looked down at the paperwork on his desk. “Oh, I wanted to tell you that there’s going to be an event this Saturday. They’ll mostly sell secondhand books, and all the money goes to charity. You can go and see if you find anything for yourself.”

“I will. Thank you again.”

Kunikida did a polite little bow, then left the presidents office. As he looked around the workplace with all the detectives, secretaries and part-time workers, he felt a sense of belonging bloom in his chest. Ever since Fukuzawa brought him here for the first time when he was younger, he was sure he’ll become a detective one day. And today he took the first step towards his goal.

He didn’t want to neglect his studies either. He was always at the top of his class, never got lower than 90% on a test before. His favourite subject was math, and if his stepfather didn’t have a detective agency, he would’ve probably become a math teacher himself. He also loved sports, and tried out multiple different ones, but martial arts seemed to be the perfect match for him. He knew he has to be a good fighter, if he wants to be an important member of the Armed Detective Agency. And he also enjoyed the strict schedule he had to follow at the dojo.

His classmates found it weird, but he loved to have a plan for everything, and follow the rules he set for himself. He had a notebook titled “Ideal”, and it was exactly that: a collection of plans, morals, rules and philosophies he wanted to commit to. And, since it was also the key for his ability, he always had it with him.

He thought about abilities a lot. On one hand, it allowed him to protect himself and others if needed, as well as being a handy tool in general. But he also knew what an advantage it was for bad people. He noticed that Fukuzawa tried not to talk about it in front of him, but he still knew about the criminal organization called the Port Mafia. It had a lot of ability users and honestly it scared him a little, but of course he didn’t want to show it. The best thing he could do was train hard and study a lot, so if he ever met a mafioso, he would have the upper hand.

As he gathered his coat and bag from the chair he left them on, he noticed a lollipop placed carefully on top of them. He picked it up, read the “lemon flavour” label, and furrowed his eyebrows. He immediately knew who to look for: Ranpo was sitting on his desk, munchin on chips.

“Did you leave this here?” Kunikida asked, to which the detective stopped chewing, and looked at him; well, he turned towards him, but kept his eyes closed, obviously.

“Yeah,” was the short answer.

Kunikida took a few steps towards him, holding the lollipop out for Ranpo to take it, but he shook his head.

“What, you think I lost it? Do you know me as the kind of person who makes mistakes?” He started focusing on his snacking again, but added: “It’s for you, dummy.”

“Oh?” Kunikida muttered, confused. But he quickly composed himself, pushed his glasses up, and put the lollipop into his pocket, where he then left his hands. “Thank you. But what’s the occasion? You don’t like sharing.”

Ranpo shrugged. “Welcome at the Agency, I guess.”

He tried so hard to look cool and nonchalant. As he continued chewing as loudly as possible, Kunikida turned to leave, hiding his smile.

He put on his coat and backpack, and started unwrapping the lollipop as he walked down the stairs. He was thinking about his usual daily routine: school, agency, dojo, then finally going home with Fukuzawa. He loved training, really he did, but this time he couldn’t wait to be done with it, so he could talk to Fukuzawa more.

As he exited the building and started walking, popping the lollipop into his mouth, he imagined himself as a detective. He would beat every mafioso in unarmed combat, up until he was old enough for a gun, and then in armed combat as well, maybe, he wasn’t sure if he ever wanted to use a gun, to be honest. But he would be so cool, leading an investigation team after a murder or something. Being Fukuzawa’s right hand.

He was always among the first ones in the dojo, but when the class was over, he was the last one in the changing room. He didn’t get on well with the rest of his group, so he usually stayed and chatted with the sensei a bit, so by the time he arrived at the changing room, the rest of the kids were already leaving. He liked it this way.

He wanted to have friends outside of the Agency, really he did, but it was difficult. Sometimes he felt like an ocean separates him from the other teens, and he sits there alone in a small boat, trying to cross the water alone because they don’t want to meet him halfway.