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Shattered Realities

Summary:

A Mairuma x BSD Crossover fic

After the Decay of Angels incident, the ADA finally has time to relax, until a new disaster strikes Yokohama; later known as the Collision.

The netherworld crashes into Yokohama, and characters from both worlds are scattered. Joining forces, both sets of characters now struggle to grasp their new reality while villains close in on them. They must find out the truth of why their dimensions merged before time runs out.

Notes:

Heya, Fox and owlkookie here! This crossover fic was started as a passion project, and we decided to mush these two series together for no other reason other than the fact that we enjoy them! :D

owlkookie~ YEAS! FOR FUNSIES :D
Fox~ Indeed! Don’t expect quality here, just a fun little thing we’re doing ^^’
owlkookie~ but you can expect procrastination, because who doesn’t love that??
Fox~ We have planned a couple of chapters, however, and will work on editing them so we can get them out! (Not expecting many people to read this; do not expect popularity but oh well)
owlkookie~ And if you haven’t watched either Mairuma or BSD, I do warn: SPOILER ALERT (don’t say I didn’t warn you because I will say I told you so)
Fox~ Oh, make sure to read the manga for Mairuma! This fic takes place after Decay of Angels for BSD, and after Iruma’s second battler party (the arc that was just finished around this time)

(See the end of the work for more notes.)

Chapter Text

Was it only 10 minutes ago that Atsushi and Dazai had been talking about some weird food combo? Beef bowls and chocolate syrup. Kenji had once suggested they try it, and the topic of conversation had veered off into something bizarre. It couldn’t have been 5 minutes ago. No, it was probably more. 10 minutes. 10 minutes ago, Atsushi had been sitting at Cafe Uzumaki, disagreeing with Dazai’s appearance-over-taste food logic. Everything had happened too quickly.

 

The reason they had run out of the cafe in such a hurry had been because of an odd, egg-shaped plant with round eyes and two horn-like things on either side of its head(?) The plant, an odd eggplant colour, had waved its hand(?) and spoke from the other side of the cafe’s window. “Hello.” The glass of the cafe window had muffled its voice. “I am the legend leaf. Nice to meet you.” It had been floating, suspended in the air, as if it had disabled gravity around it. 

 

Atsushi had stared in shock, his mouth falling open (a disgusting piece of food flopped out), and sat frozen, unable to tear his vision from the purple thing floating by the window. 

 

It had taken notice of the spit-covered food, and, not taking its beady eyes off of Atsushi, intoned in a dull voice, “Ew. You should learn some manners.” before floating off out of sight of the window into who knows where. 

 

Now, Atsushi was outside, taking in a scene of absolute chaos. Buildings crashed without reason, bobbing around the sky like heavy, opaque clouds of concrete. There were strange, indescribable objects floating around and animal-like beings roaming the ground as well as the air. The screeching of various beings, the crashing of buildings as they collided with one another, and the wailing of sirens filled his ears. When he lapped the air, activating his tiger senses, metallic sawdust coated his tongue. Atsushi squeezed his eyes shut, trying to recall the peaceful atmosphere and the smell of coffee always present in Uzumaki Cafe — he missed and longed for it already.

 

Standing a ways from the Agency’s building, Atsushi marvelled at the hovering trees in horrified fascination. “Dazai-san,” he whispered, “what’s…going on?” The lame question was all he could ask in the face of such a bizarre site. Dazai didn’t respond. “Dazai-san?” Atsushi whirled around to look where Dazai was standing — or should have been standing. 

 

Dazai was nowhere to be found. And, to Atsushi’s shock, neither was the Agency building. What the…

 

He darted over to where the Agency building once was. There was nothing but the concrete foundation where it had once been. There was no trace of the building itself or Dazai, anywhere. 

 

Atsushi felt like his mind was going into overdrive. Being in the ADA had taught him to stay calm in the most bizarre situations (and yes, that meant ignoring the gigantic shark-pig currently rampaging down the street). Atsushi took a steadying breath and closed his eyes, trying to think through various scenarios for what might have happened to Dazai.

 

Just as he began to give up on his pointless thought experiments, a crumble sounded behind him. Atsushi looked over in time to see the Agency’s office falling from the sky as if it had been picked up by a giant’s hand and dropped again from a great height. The missing Dazai was standing directly under it, staring up with an unsettlingly calm expression and not moving an inch, despite the impending doom about to befall him. Chunks of rock and wood were showering the ground in clinking waves.

 

Immediately, Atsushi felt Byakko take over. Within barely two seconds, his legs had smoothly transformed into those of a white tiger’s, and he pushed off the ground into a mighty dash, using his momentum to grab Dazai and leap out of the way mere seconds before the building smashed into the ground where he’d been standing. 

 

Panting from his swift rescue, Atsushi exclaimed, “Dazai-san, that could have been dangerous! Why didn’t you—” Cutting himself off, the boy sighed in exasperation. He did know exactly why Dazai hadn’t jumped out of the way before the building crashed down.

 

Dazai huffed and crossed his arms, mildly annoyed, saying, “That would’ve been a perfectly fun way to die.” 

 

“Dazai-sa—” Ignoring Dazai’s pouting, Atsushi thought he felt a faint tremor in the ground. He paused. “What?” Dazai uncrossed his arms and gestured for Atsushi to put him down, which he did, slightly flustered. An ominous rumbling made Atsushi’s heart jump, and he shrank closer to Dazai, his arms positioned protectively in front of his torso. “What was that? An earthquake?” Dazai ignored his questions and didn’t seem surprised in the slightest; he was walking, hands in pockets, whistling to himself. 

 

Atsushi’s heightened tiger senses picked up on something crashing in the distance, followed by the howling of sirens and shrill screaming. Dazai didn’t turn his head. 


Why in the world is Dazai so calm? Did he predict this would happen? Atsushi thought as a ramen food stall floated by. He narrowly avoided getting broth spilled on him as a bowl tipped over, spilling its contents everywhere. He sighed before turning and walking forward—

 

Hold on. Floating ramen stand? Atsushi felt his consciousness doing a double take as it reanalysed his surroundings. Right. Buildings in Yokohama were missing or floating around, including this ramen stand, strange animals running amok, and a lot of screaming that was overwhelming his senses.

 

Atsushi felt like something inside him was cracking, slipping away. That was probably his sanity. Dazai whistled, strolling ahead of him, not a care in the world, even if said world seemed to be falling apart right in front of him. 

 

An abnormal screeching noise made Atsushi jump, interrupting his thoughts and causing him to emit a — rather unmanly — screech in response. In his defence, the sound was rather freaky, and his body had long shifted into danger mode, his tiger-enhanced senses pinging at the slightest disturbance in the air. 

 

And currently, many of those were happening simultaneously, meaning Atsushi’s concentration was all over the place. 

 

The first thing that came to mind was someone in trouble. The scream sounded far from human. Was someone being attacked by one of those strange creatures? Ears perked, he followed the sound to a yellow, bird-shaped object with a blue tuft of hair on its head. The debris of what looked like a piece of furniture — perhaps a small nightstand? — was scattered about it. There wasn’t a human in sight. The bird screeched again, even louder this time, and Atsushi felt his tiger-enhanced ears ringing from the shrill noise. Without thinking, Atsushi brought his tiger-enhanced fist down on the horned bird’s head, smashing it. His nerves were beyond frayed by this point, and something akin to frustration was causing him to act up. Grimacing at his impulsiveness, he called, “Dazai-san!”

 

Dazai, who was still by the flying ramen stand, turned and started walking in Atsushi’s direction when he bumped into seemingly, nothing. Only when Dazai stumbled back, brow creasing slightly, did someone with flat, alabaster hair appear out of thin air . For a second, nobody moved, all equally shocked. Atsushi remained frozen to the spot, his mind spinning a mile a minute, thoughts whizzing about his head. Who is this person? Are they an ability user? Why do they have horns and wings? What— Atsushi firmly cut off his wild train of thought, trying to focus. 

 

The closer he looked, the more the boy seemed less and less like a human. Small horns and wings poked out of his head and back, and he was wearing a bright blue school uniform, which no one would ever see in a place like Japan. He held a trumpet in one hand. 

 

Behind him, Dazai had paused and had a faraway look in his eyes. Perhaps he was analysing the situation? Dazai seemed to come back to himself a little, and opened his mouth, perhaps to call out, only for Atsushi to cut him off with an alarmed hiss, hackles raised. 

 

The boy had vanished without a trace. Not even Byakko could sense his presence. 

 

“Well then, Atsushi-kun,” Dazai’s ever-calm voice rang out from in front of him, “looks like we’ll have to go searching for our new friend Ghost-kun.”