Summary: Chuuya knew things were wrong. He stared at the bottle of pills in his hand. It was time to make a move. Beast AU.

Chuuya dealt with a sense of wrongness that steadily grew. First… they were faint feelings that briefly disoriented him. Those weren't too bad; He was able to deal with them.

The problem really started at age eighteen, the thoughts. Thoughts that were right and weren't.

The person leaving his office should be Akutagawa, not Atsushi.

Dazai, not Mori, should be sitting at that desk.

Gin should be part of the Black Lizards.

Then he saw Kyouka and Atsushi walking down the hallway. He clenched his fist to stop himself from reacting. His eyes grew glassy.

Kyouka should not be here either.

But there was the main one, the first one, where it had first started. That one was the worst. He could feel the whispers grow louder, shrieking at him how wrong it was whenever he saw the man.

Oda should not be in the Armed Detective Agency, and certainly not alive and well. Oda should be dead.

Chuuya knew, somehow, that he was right and the world was wrong. But… that sounded crazy, didn't it?

The flashes grew worse. He couldn't go through a day without freezing at the sight of his coworkers. It wasn't good.

He decided to go to Dazai. Maybe his genius a*shole partner would know what was going on, what was wrong. Dazai almost always knew.

XXX

There were constants in each world, universal constants that Dazai learned. For him, there were two: Odasaku would always die. Chuuya was always his partner- he always trusted Dazai without hesitation.

He had been trying to change the first constant for a long time.

He tried everything. From not befriending Ango to killing him, leaving the Port Mafia to staying, not finding Akutagawa or Atsushi to bringing them both to the Agency, leaving Chuuya in the Sheep longer to having Mori pick Chuuya off the streets right after the Arahabaki incident, crushing the Armed Detective Agency to making it flourish across Japan, killing Fyodor to letting him win...

It was the first time Dazai had done it right. Odasaku didn't die. He figured out the combination for Oda not to die. Kill Mori, never befriend Oda, get Atsushi to join the Port Mafia, force Akutagawa to join the Agency...

He had been through this type of timeline so often, over and over until it had grown dull. The only exciting thing was that Oda was still alive, farther than any other. And that spark of life was worth protecting, even if Oda didn't know him.

But there was something new. He listened with rapt attention, hidden by a lazy yawn to infuriate Chuuya. He hadn't expected Chuuya to get visions of the other worlds. It was probably because of Chuuya not being human, something to do with really being Arahabaki.

"You want the flashes to end, right?" Dazai smiled. It was time to take advantage of the perk of being the other half of Double Black-trust. He shook the unmarked bottle and lobbed it to Chuuya. The blue gel pills rattled inside. "Then take these."

"You're sure?" Chuuya asked, doubtfully. He felt his instincts screaming at him even as he just held it.

Dazai hummed, putting a finger to his lips. "Yup. I know because I had those things myself. Mori-san gave me these." The second part was a complete lie. "There are no side effects, aside from maybe sleepiness."

Chuuya opened the cap and took one out. It was ocean blue, the same color as his eyes. He pushed through and dry-swallowed one.

Dazai smiled, a sort of catlike satisfaction on his face. "It'll take some time to work. Take one every few hours?"

"Few?" Chuuya questioned.

Dazai shrugged. "Like say, seven or eight?"

XXX

Chuuya took the pills on a regular basis. They worked. The flashes ended. But the sense of wrong stayed, festering and growing in his subconscious. He went on with life as usual.

A mission ran long, several hours of nonstop fighting. He was on the city outskirts, no time to get the medicine.

The medicine weakened.

The buildup of sensations and thoughts all about the wrongness smashed through the cage in Chuuya's mind. They weren't from his human side, he knew that. They burned as they ran through him, a taste of black fire.

Akutagawa. Dazai. Mori. Gin. Atsushi. Kyouka. Oda.

He remembered all of that. They were different here. It was not how this world should be. He knew he was right. Chuuya knew all of the things that were wrong.

He stared at the blue pill in his hand. It was time to make a move.

He couldn't fix what had been done. But he could change what had yet to happen.

He popped the pill in his mouth. He had to stay medicated for now. He couldn't risk Dazai knowing something was off.

XXX

Chuuya knew the knife of betrayal well. Hirase and the Sheep drove it between his ribs years ago. He had it used on him by so many people, mainly his coworkers that turned out to be spies or tried to use him to get a higher position. He was a rather open person, and people tried to take advantage of that.

Now, Chuuya was the betrayer, for once.He had never betrayed someone himself. He was always the loyal one, the person who would trust someone to the end.

He knew that as he deliberately turned his back to an attacker, pretended to be unaware of the armed enemy. He knew that as he felt the bullet ram through his side.

He felt as if he was driving a knife into Dazai's back, twisting the blade to drive it in deeper. There was no going back after this. Dazai hadn't noticed it yet, but he would soon enough.

He clenched his teeth, slashing his knife through his attacker's throat.

Chuuya had gotten shot, on purpose, not that anyone knew. He was given sick leave by Dazai, although he had protested it. Well, he had given up the front of protesting, but he really needed the time.

There were benefits to being seen as dumb, when you just had no interest in playing. It meant that when you actually were doing something, few people actually noticed.

He weaned himself off the pills. He got used to the flashes, learned how to draw on them and how to figure out what was going on. So many of them were different, different versions of people Chuuya knew on different sides of the law. Many of the scenes weren't pretty, too often full of blood and, foremost, people screaming before death. The thoughts… they were more useful.

XXX

This was the end of Dazai's plan to keep Odasaku alive. For that… He had to die. He got to die. He wouldn't be able to see Odasaku live, he wouldn't be able to see any future books that Odasaku might publish.

But death was such a small price to pay. He got to see Odasaku in the Agency, able to live as a good man. He read his friend's book, the only one written by Odasaku in all of the timelines.

Death… death was such a small thing compared to the rest of life. Only a small part of it, the end. Dazai smiled. At least the middle was amazing.

Dazai had his back to the edge of the rooftop. He could feel the wind whipping around him, tugging at his clothes. The exhilarating feeling that he was about to fall and die… soon. He was facing his apprentices, finishing up what he needed to tell them.

He was shoved harshly from behind. He stumbled and fell forward, landing on his knees and hands. He almost scraped his face on the rooftop concrete.

"You don't get to take the easy way out." It was not a suggestion, it was a statement, a fact. He would do whatever necessary to keep Dazai alive, even against his will, like usual.

It was a familiar voice that Dazai recognized immediately. But the sentence was said coldly and all too knowingly, a foreign tone to his ears. Dazai frowned, "Chuuya… why are you here?"

"I decided to alter the end of your plan."

Dazai stood up, his back to his partner. "You stopped taking your pills." That wasn't right. Chuuya was acting as an enemy. Chuuya was taking it upon himself to act against Dazai. It was probably just a misunderstanding. He simply needed to smooth things out and everything would return to normal.

"There was something wrong. I knew it." Chuuya's eyes were hard. "You should have told me before."

Dazai stared at the sky. 'I should have expected the backlash,' he thought. 'I should have expected that, when I broke one universal constant, I broke the other.' He stayed silent, his tongue twisted. He had never had to deal with Chuuya like this.

"Chuuya-san, what's going on?" Atsushi asked. Him and Akutagawa were still there, he was still staring at the older men in veiled shock and confusion.

"Why'd you save him?" Akutagawa asked. There was a sort of curiosity and dark dissatisfaction in his gaze.

"He doesn't get to die," Chuuya simply said.

The 'why' died on Akutagawa's tongue, unspoken. He saw the expression on Chuuya's face.

Dazai turned around. He needed to look at Chuuya, otherwise he was working half blind. He was still thinking of this as more of a minor inconvenience to throwing himself off the roof. After all, he simply needed to rile Chuuya up, then appeal to his partner's reason, and that should be as easy as usual. The situation was salvageable.

Chuuya grabbed Dazai's collar, pulling his partner's head down to his eye-level. "You don't get to screw everyone over for Oda and leave, Dazai. You made your bed, now lie in it," he quietly hissed.

Dazai's face twisted before settling into a blank, dead expression. 'Oh. Chuuya knew everything. There's no stopping him now. He's not going to let me die, no matter what I say.'

"Glad you get it, a*shole," Chuuya grumbled, letting go of Dazai's collar.

Dazai straightened up. He fixed his collar absentmindedly. He clutched his cheek. "Chuuya," he whined.

Chuuya had slapped him. "That's for your s*it plan to mess up everything." He glared at his partner. He was still mad, but it had abated some.

Dazai was operating in the dark, still clutching his cheek and trying to piece together his fractured mental picture of Chuuya Nakahara. Desire, that's the main thing he was missing. "What do you want?"

"One thing," Chuuya said, his voice growing restrained, quiet.

The Chuuya that insulted Dazai was familiar. The Chuuya that played the fool was smirked at. The Chuuya that growled he would kill Dazai was laughable and welcome. The Chuuya that overflowed with rage and power only received an approving smile. The Chuuya that restrained his thoughts, exercised his iron will, and wreathed himself in an aura of calm reason was… unsettling. His blue eyes contained the fury of an ocean hurricane and the smallest wave lapping gently onto a shore.

Dazai narrowed his eyes, incredulous. His amber eyes darkened. He was disturbed by all of this… change in his partner. Change that he knew he had unknowingly caused. "One?"

Chuuya folded his arms, laying out his demand. It was his one and only demand, and he wasn't lying. "You can't exactly fix things, but you can make them better."

Dazai sighed. "Killing myself would be so much easier, then I wouldn't have to deal with this," he mourned.

Chuuya irately replied, "We've been over this already."

Dazai puffed out a breath of disappointment. "So we have. What things do you want changed?"

"I'd say you not being an a*s, but I think that's impossible for you."

Dazai threw a hand over his heart. "Me?" He replied innocently. It looked odd on the face of a terrifying mafia member, but also strangely normal.

"Dazai, I don't even know where to begin. The list of the stuff you've pulled is a f*cking mile long."

"Umm, what's going on?" Atsushi asked, having worked up the courage to interrupt his superiors who were arguing like children.

Dazai tilted his head. "We're sorting out how the Port Mafia will be run from now on, and apparently how my personal relationships with every ability user in the city needs to change." His voice was chipper, oozing with false enthusiasm.

Chuuya snorted. "Well, you're not exactly wrong."

Akutagawa turned and walked away. He wasn't suicidal enough to try his hand at taking out Chuuya.

"Akutagawa?" Atsushi asked. He gave a look towards his superiors before following his temporary partner inside. He needed to go find Kyouka.

"For one demand, you managed to bundle a lot of demands in there," Dazai dryly said.

"Your fault for causing so much trouble," Chuuya shot back. He hesitated before promising, "Look, I think we're in the clear. Oda's still alive. We'll figure out things down the road if we need to and… and I'll… I'll help you keep him alive."

Dazai smiled.

"Now come on, I'm freezing," Chuuya grouched.

Dazai cast one last look at the edge, the tempting edge. Then he turned and went inside, listening to his partner grumble about different things going on in Yokohama. He knew Chuuya would just catch him if he tried.

A/N

The idea for the pills comes from Azurelitestar, specifically his/her story Carpe diem on Ao3.

-Silver