Disclaimer: Bleach belongs to Tite Kubo. I assure you I am not him.

This is way AU. Might not make much sense if you haven't read some of my other stuff.

Covalence

A Bleach Fanfic

Chaos Theory AU

Chapter One: Summer Pear Tree

Karin slept on the side of the barracks that allowed predawn light to filter in through her window. She had initially resented this fact, but eventually she'd learned to embrace it. Being up first meant all the water was still hot, and she could eat breakfast without having to stand in line for it.

Still, it did mean getting up annoyingly early in the morning.

"Ugh." She rolled over on her futon, scrubbing both hands down her face. The stupid birds that lived in the tree outside her window were chirping obnoxiously. There was no hope of falling back asleep for even a few more minutes now. Throwing her blanket off herself, she flinched at the sudden cold—October was not her favorite month. Winter would be here pretty soon.

Fortunately, being eighth seat meant getting her own room in the barracks, and a decently-sized one at that. So no one cared that she slept in a ratty old living world tee shirt and shorts, or bothered her about the fact that she sometimes didn't put her laundry away when the Fourth brought a clean stack by.

Speaking of which… she grabbed the kosode off the back of her desk chair and sniffed it. Nope. Giving it a toss into the hamper near the door, she stumbled over to her closet and pulled the door open, blinking at her half-dozen identical uniforms without enthusiasm. Black on white. Not even the cool sleeveless ones the Ninth had—Renji had neglected to mention that detail when she was deciding between divisions.

It wouldn't have actually made a difference, but she made a note to rib him for it later anyway.

Even better than having her own sleeping quarters, being an officer above tenth seat meant she got her own bathroom. Just a small one, nothing fancy, but she didn't have to share it. Karin had only realized after moving into the barracks that sharing things with Yuzu in childhood had not actually prepared her to share them with strangers. For one, Yuzu was clean. For two, she wasn't an idiot.

Night and day from some of the numbskulls around here.

Karin didn't feel quite human—well, whatever—until she was scrubbing a towel through her wet hair. She hated it when the water soaked into her uniform collar, so she pulled it up into a decent-looking ponytail and swished it around a few times before pulling on her shitagi.

The last thing to go on was her red silk sash, with the big fat Quincy cross on it that most people didn't recognize. She wasn't sure she'd ever tell Uryū, but wearing it around the Seiretei gave her a perverse kind of satisfaction. It helped that it was so obviously not a regulation item. Usually the only people who got away with that were vice-captains, captains, or in the Eleventh Division where no one gave a shit.

Kuchiki had never said anything to her about it, though.

Attaching Hisaku to the strings on the sash, Karin brushed her fingers over the katana's tsuka. The warmth was familiar by now.

Now for one of the fun parts of her day.

Sliding her door open and stepping out into the hall, Karin checked the clock on the wall to confirm the time, then took in a deep breath.

"All right! Up and at 'em, slackers! Those drills aren't going to practice themselves!" She banged the side of her fist on each door as she passed down the hallway. "Look alive, Sixth Division! Don't wanna get chewed by the fukutaichō, do you?"

As the officer in this hallway, she was responsible for waking up the rest of them for drills, which she did not have to attend. Well… responsible might have been a stretch. She could let them be late. But they were her direct subordinates, and she didn't want them to make her look bad. Not in a division where the captain actually took personnel reviews seriously.

She grinned—if only to herself—at the chorus of thuds, curses, and groans that reached her through the doors. "Quit your complaining! It wouldn't suck so much if you were up earlier by yourselves!"

Shaking her head, she headed to the mess to grab breakfast, then to her office. She did have to share that—only Renji and Kuchiki had office space to themselves. Karin shared with the ninth seat, a girl named Mihane. She was quiet and serious for the most part—at least that made it easy to get work done.

"Oy, Kurosaki."

Karin glanced up, abandoning her effort to find her office key on the ring. She'd known it was Renji, obviously; she still grinned at her vice-captain nevertheless. "Morning, monkey-brain."

He rolled his eyes and scowled at her. By this point, it had the air of mere rote. "We good for soccer practice tomorrow?"

Karin nodded. "Yeah. You found us a goalie yet?"

"I think one of the twentieth seats is gonna do it—Kanda."

"The guy with the mustache? He might be all right." Pretty much no one in Soul Society knew the rules of soccer, and so far, their division was the only one with even close to a full team, but apparently the Seventh was interested, and Renji swore they could get the Eleventh involved if they sold it right.

"Yeah. Anyway, don't forget the forms for your review. Kuchiki-taichō wants them by this afternoon."

Karin arched a brow. "You mean he's actually going to be here this afternoon? I thought you said he leaves."

Renji shrugged. "He does, but not when there's other work to do. Just try getting them in before noon. I'm gonna go collect the testimonials from your team, so it's better if they all go in at around the same time."

Two years seemed like a pretty short window before her first review, by Soul Society standards, but Karin wasn't worried. Her team liked her, and she did her crap on time and without needing to go back and correct it. She already taught the beginner zanjutsu drills for the squad, too, so it wasn't like anyone could say she wasn't working hard enough.

"Yeah, all right."

He nodded, she mock-saluted, and they parted ways.

Mihane was already in the office, so Karin didn't need her key after all.

"Morning, Shirogane-san," she said, plopping herself into her desk chair and eyeing her stack of paperwork.

"Good morning, Kurosaki-san," Mihane replied amiably, pausing in her steady writing for only a moment before she resumed.

With a sigh, Karin went fishing for her review forms. It wasn't a huge stack—there was basically one where she filled out what her duties were plus any extra stuff she'd taken on, and then the questionnaire. That stuff combined with the opinions of her team and her officers was pretty much it.

Well, she'd better get started.

"Kurosaki-kun."

Taking the captain's bland acknowledgement as permission, Karin stepped over the threshold into his office. Aside from the bookshelves on either side, it was pretty minimalist—and really freaking clean. Probably even dust was scared shitless of the captain; it wouldn't surprise her. Lots of people were, after all. Karin wasn't afraid, really, but she also knew better than to be casual with him like she was with Renji.

"Kuchiki-taichō," she said, bowing. "I brought my review forms."

He inclined his head, extending a hand to receive them. Once she'd handed them over, he set them aside, folding his hands atop his desk. "How do you find the division, Kurosaki-kun?"

"…sir?" Karin let her confusion show on her face.

He blinked at her. "Its character. Do you find it… suitable?"

Karin furrowed her brows and crossed her arms. Was this some kind of test or something? "I think the division's just fine, sir. We do our work, we're willing to help each other out, and we can take things seriously when we have to. No one slacks off in my class, and no one gets pissy because their superior officer is a girl, so I have no complaints."

A tiny line appeared in the spot between Kuchiki's eyebrows—probably her language had done that. Not like she cared; Karin respected her captain, and showed that in the ways that mattered, but she didn't try to change who she was.

"I see," he replied.

He didn't dismiss her; she was left to shift her weight from foot to foot and wonder what else he could possibly want. He read through her forms right there, carefully scanning each page before turning to the next with a soft rustle. Karin wasn't normally one to get nervous, but there was something damn off-putting about this.

"Sixth Seat Ajibana has informed me that he will likely be retiring within the year," Kuchiki said. "When the time comes, I suggest you apply to take the position, if you find the division to be as agreeable as you say."

Karin's brows headed towards her hairline. Had he just implied that he'd promote her if she wanted it? Hell, she'd already jumped ten seats in one shot within two years; she thought she'd be stuck at eighth seat for another decade or so.

"Your work in the Hell incident was by all accounts impressive," her captain continued—either oblivious to her surprise or choosing to ignore it. "Of course, I cannot promote you on the basis of something that did not happen. But if the reports of your subordinates are as I expect them to be, that should not be an issue."

He lifted his eyes to her then. "You are dismissed, Kurosaki-kun."

"Uh… sure. Yes, sir." Karin shook her head; bowing a second time, she left his office behind.

Sixth seat, huh? She kinda liked the idea of that.

Karin sighed—more from satisfaction than anything—and flopped back onto the grass. Yuzu made a damn good bento. Enough to feed three people, too, which was good since the monkey tended to mooch.

He snorted at her from the left, but she was too content to care just now.

"So Kuchiki-taichō said I should apply for sixth seat," she said, folding her hands behind her head.

"I know," he replied. "He asked me about it a few days ago."

She tilted her head so she could look at him from the corner of an eye. "You're not fast-tracking me because we're friends, are you?"

He frowned at her, unfolding his legs in front of him and leaning back on his hands. "Like hell I am. You think I'd risk my career to jump you a few seats? We're friends, kid, but I ain't an idiot. You're moving up because you deserve to."

"Good." Karin nodded, satisfied.

Watching the clouds pass by overhead, Karin decided that they probably wouldn't be able to take lunch outside much longer before it got too cold. Her dad was already talking about how this winter was going to be a really bad one—apparently a temperate summer was a sure sign or something. Karin couldn't say she bought his so-called logic; she'd sensed a chill in the air earlier than usual all the same.

"So when do you think all this Aizen stuff is gonna come back to bite us in the ass?" she asked suddenly.

Renji sighed. "I dunno. It's been almost five years. That's only half what they said, but… it kinda feels like something's about to happen, doesn't it?"

Karin rolled her eyes. "It always feels like that."

He grunted in reply.

"Still, I mean… I wouldn't say no to another few years to train, but… it kinda feels like something around here's gonna snap if we don't have something to do soon." She pulled one of her legs up, planting her foot flat against the hillside.

"How's the training going, anyway?"

Karin pursed her lips. "Decent, I guess. I'm working on another shikai technique, but it's a pain. Especially when no one except you will train with me."

Uryū probably would, but the Eighth was still busier than most divisions; the fact that he managed to eat dinner with her and Yuzu most nights was a small miracle. Yuzu didn't have as much flexibility about her duties; she had to follow Unohana around all shift every day, basically. The rest of the Sixth's seated officers weren't too excited about the possibility of burns—she trained against them only with Hisaku sealed. Most people didn't have shikai anyway; it was only a requirement for tenth and above.

Renji scratched his chin. "So basically you need someone who's fine with you trying to fry 'em, right? Besides me."

She huffed a laugh. "Basically."

"I think I know a guy."

She wasn't quite sure what to make of Yumichika. Ikkaku wasn't that hard to figure out—he was basically every Eleventh Division stereotype she'd ever heard of shoved into one body. But something about Yumichika was sly—like he knew more than one thing he wasn't saying.

Regardless, it was the other one she was going to fight, so it probably didn't make much difference. Ikkaku was a bald guy with a sharp face, though Renji had told her it was probably better if she just didn't mention the bald part. Apparently, he was strong even by third seat standards, but didn't really have any snobbishness about it—he'd fight anyone who promised to be entertaining. Most importantly, he wouldn't hold back—not because she was young, not because she was a girl, and not because it was only a spar.

Karin worked on her techniques as often as she could. But if her time in Hell had taught her anything, it was that they didn't always click until she needed them to. So this arrangement was pretty much perfect, risk of grievous injury included.

They took their places in the ring, bowing. Neither wasted any time with sealed zanpakutō—both she and Ikkaku went right for shikai. His was a spear of some kind, it looked like. Definitely a reach advantage, at least in terms of the weapon alone. Karin used Sakebe right off the bat, lighting Hisaku on fire. Having the flames already there would save her the time of creating them.

She stepped into shunpō. Her attempt to strike Ikkaku's shoulder was stopped cold by the spear-pole, and she had to hurry to get out of the way of his retaliation.

He was even more aggressive than Karin typically was in a fight, and faster than he looked. She didn't even sense him appear behind her until she felt a physical disturbance in the air. Sidestepping quickly, she just barely avoided being stabbed in the guts by the point of the zanpakutō. Karin hissed when it cut across her thigh instead, long but shallow.

Karin disengaged and flashed away. Ikkaku followed. She saw the crooked grin stretching his face and wondered if maybe she wasn't in too far over her head after all.

But of course not. Renji wouldn't have suggested this if he didn't think she could manage. Besides, she'd just been thinking that she needed more pressure. Trying not to get impaled definitely qualified.

Ikkaku swung again; Karin met the spear with Hisaku, using Aoge to throw fire point-blank at his face—like she'd done with Shuren. To her surprise, the pole of the spear snapped in half; Ikkaku lifted the bottom end with the red fur thing to sweep away the fire before it reached him. It had pieces?

Well, shit.

Now that the cat was out of the bag on that one, Ikkaku didn't bother trying to hide it. "Quit… running!" he shouted, lashing forward with the bottom half of his weapon; he was trying to tangle her feet with the chains connecting the segments.

Just a little more…

Karin was pushing her shunpō to the limit just trying to stay ahead of him. She needed an advantage—distance wasn't it, strength wasn't it. So she had to be faster.

The spear-point came flying for her; Karin ducked in just enough time to hear it whistle past over her head. A short, sharp tug at the end of her ponytail gave away that not all her hair had survived. Talk about a close call. She slashed twice with Hisaku, hurling a double-dose of fire at Ikkaku.

He cut right through the first one—but she'd packed more reiatsu into the second, and he had to get out of the way. The sleeve of his shihakushō caught fire; in the time it took him to put it out with his reiatsu, Karin repositioned. Throwing more fire at him from the side, she followed it in, gripping Hisaku with both hands and slashing down.

The blade swept through nothing but air—Ikkaku had flashed away.

Honestly, it was only the fact that he was laughing that clued her in to where the next attack was coming from. The Eleventh really was… enthusiastic. Raising Hisaku to block, Karin braced her free hand on the back side of the blade. Locked in place against a stronger opponent, she shifted her balance, giving up on the contest of strength and trying to turn it around by swinging a kick in from the side.

She caught Ikkaku's midsection, but not hard enough, and he jabbed her in the stomach with the blunt end of his zanpakutō. Karin's wind left her in a rush; she doubled over. The follow-up caught her across the back, sending her flying. She landed hard a good dozen feet away, sprawled on the dirt.

Faster, faster; she had to move faster, or he was gonna end this in one more shot.

He disappeared from her senses briefly—he was coming in for the win, she knew it.

Move.

The voice in her head was Hisaku's—a command, not a suggestion.

Karin moved.

The ring's bizzare, broken-building landscape flew by faster than she was prepared for. She hit the ground after her jump harder than she'd intended, tripping and rolling to a stop at least half again as far from Ikkaku as she'd meant to. There was a crack in the ground where she'd been seconds ago.

Get up.

With a groan, she pushed herself to her feet. She felt… light—like gravity mattered less than usual. Like she could spring off the ground and run on the air. It wasn't quite the same as shunpō, though. Karin looked down at her feet. To her own surprise, they were edged in Hisaku's red fire, formed into little wings on the outside.

This was it. This was the technique she'd been trying to figure out for months.

She grinned. "Tobase, Hisaku." Launching herself forward, she wheeled around behind Ikkaku and slashed.

He blocked, but not nearly as easily as before.

This was gonna be interesting.

"I told you I can walk, monkey," Karin groused. She didn't attempt to push away from Renji again though. Her feet were killing her.

"Yeah, yeah, I know." He didn't mention it.

Beside them, Yumichika was not helping Ikkaku walk. But then, most of his injuries were to his arms and torso, including the one that had ended the match—a big burn square in between his shoulder blades.

"You sure you don't want to join the Eleventh?" the bald man asked, rolling his shoulders. "We've got an open seventh seat you could probably make."

Karin knew she hadn't beaten Ikkaku, but the acknowledgement felt pretty damn good. "Don't you guys have some kind of rule against kidō-type zanpakutō? Elemental counts."

Ikkaku rolled his eyes. "You honestly think Zaraki-taichō gives a flying fuck what kind of zanpakutō his subordinates have? The Eleventh is about attitude: if you love to fight, and you're good at it, then you're welcome to do it with us."

Yumichika wore an unreadable look behind Ikkaku's back; eyes slightly narrow, mouth downturned. Karin wondered if he disagreed or something. In any case, he made no comment.

"Eh, thanks," she said, shrugging and then regretting it when she pulled a wound. "But I like things just fine where I am."

"Damn straight. You can't have her, Ikkaku—I ain't losing a forward on my team."

Karin elbowed Renji in the ribs. "What you mean to say is I keep you sane."

"Is that what they're calling it now?"

Yumichika was smirking at them. Ikkaku just shook his head. Eventually, the large medical building that served as the Fourth Division hospital came into view, and they shuffled inside.

"I fuckin' hate it in here," Ikkaku muttered, glaring at a knot of unseated shinigami. They flinched and made themselves scarce in very short order.

"Ikkaku," Yumichika said, arching a neat eyebrow.

Ikkaku scowled, saying something else too low for Karin to hear. But he didn't make any further fuss.

Given that a fukutaichō was among them, it wasn't surprising that it was Isane who came out to investigate.

"Abarai-san. I hope you aren't—" her eyes moved to Karin, and she blinked. "Ah, I see. Madarame-san, please come with me. Karin-san, I'll get Yuzu-san; I believe she's free right now."

Ikkaku went with Isane, if grudgingly; they disappeared around a corner.

Yumichika settled in one of the chairs in the front room, shooting an amused look at Renji. "What did you do to make poor Isane-san think you need looking after?"

"Nothing."

Karin raised an eyebrow at the reply. Yumichika slid his eyes to her; she shrugged.

"Don't look at me; I don't usually hurt him bad enough to justify a trip here."

"Karin!" Yuzu's voice was tinged with concern.

She turned to her sister, still across the entranceway. "Uh… hey Yuzu. Don't suppose you can take care of this, huh?"

Yuzu sighed. "Come on, then. Thanks for bringing her by, Abarai-san." She smiled at him, nodding politely at Yumichika as well. "Ayasegawa-san."

Karin followed her back to one of the exam rooms, pulling herself up onto the metal table even though her arms protested it. Her legs were a little worse off still.

Yuzu's mouth pursed. "Training?"

"Yeah. Finally got that new technique down; the one I've been working on." Karin pulled down her kosode and shitagi; Yuzu would want to deal with the worst wound first, and that one was just above her hip.

Her sister winced when she saw it—but her sighs were sighs of resignation, these days. "Well, that's good. Do you think you've learned all the techniques for your shikai?" Yuzu's hands lit with kidō; Karin could feel her reiatsu returning to normal levels, little by little.

"I think so. I mean, I could still be better at using them, but at least I know what they are, now." The gash in her abdomen itched while it closed—Yuzu was using a painkilling kaidō with the healing, but by her own admission still had some work to do to master it.

Considering the alternative, Karin could hardly complain.

"How about you? Any more ideas about that weird thing you did with Jinta?"

She'd heard the story—even if she didn't understand exactly what a Hell Chain was, being able to get rid of one was clearly important. It was what those rebel guys had wanted in the first place. Even if Amari had said it wouldn't actually free them.

Yuzu frowned. "Not really. Unohana-taichō is helping, but it's…" She trailed off, moving to Karin's next injury.

"Hm. Well, if there's anything I can do to help, just let me know."

That got a smile out of her, at least. "Of course, Karin."

Renji was still waiting for her when she left the hospital room, so they decided to go back to the Sixth. Karin still had a few hours before dinner, and doing her review paperwork that morning meant she had more to get to between now and then.

The Seireitei was honestly a massive place; most of the Divisions were located close in towards the center. Because of that, she sometimes forgot just how much open space and stuff there was inside the walls. Towards the outside, where the nobles had their estates, there were even forests. But she spent so much of her life these days in such a small piece of it.

Not that she's wandered around much living in the Rukongai either; but at least the people out there were a little more… diverse, compared to one another. In here, it was soldiers and nobles and their staff. That was about it. It was also mostly men, come to think of it.

"Do Ikkaku and Yumichika have a thing?" she asked abruptly.

Renji didn't seem surprised by the question, exactly. "A thing?"

"Yeah. You know, are they involved, or whatever you wanna call it?" She hesitated to use the word love, because it had so many meanings. For all she knew, it might not even be what they called the thing.

He nodded. "Kind of. They're complicated." A pause; he continued slowly. "Do you find it weird?"

Karin pressed her mouth into a line. "Only because no one talks about it." He probably meant the fact that they were both men; Renji knew she was from the living world, where opinions on that kind of thing… varied. Karin couldn't have cared less if she tried. "In general, I mean. Not just them. Like… almost no one here is married, or even seeing anyone. Or has kids. Most people in the Rukongai do eventually." Most of them couldn't shut up about those parts of life, even.

Renji relaxed slightly. Lifting his arms, he folded his hands behind his head. "You're not wrong," he said, exhaling from his nose. "It's especially uncommon in the upper ranks. I only know of a few seated officers who are or have been married or whatever. Kuchiki-taichō was, before I met him, but nobles are different."

"I don't get it," Karin said. "I mean, it's not like I think people should be focusing on that crap when there's a war coming or whatever, but I guess… I still thought some of them would be, you know?"

"Most people are afraid to be involved that way," Renji replied. "It's discouraged. The Sōtaichō believes that the way to be the most effective soldier is to harden your heart. It's not illegal to date or get married or whatever. And believe me, plenty of people are, uh, 'involved.' But anything that could screw with your loyalties or priorities or willingness to follow your orders…"

"That's complete bullshit," Karin said, crossing her arms as she walked. "By that standard, my loyalties are already screwy—I told everyone that in my stupid interview!" She'd straight-out said that her family was the most important thing in the world to her. It didn't get any less 'division-first' than that. "Kuchiki knows, and he still promoted me."

"Yeah, well… not everyone agrees with the Sōtaichō, you know. But some kinds of disagreeing are seen as worse than others. Usually if you want to get married and have kids, you retire—and you hope that you're not dangerous enough that the Onmitsukidō drags you off to the Maggots' Nest later." Renji's mouth twisted. "But if you're smart, you'll keep anything like that under the radar, especially if it's with another soldier."

Karin snorted.

"I'm serious, Kurosaki," Renji warned. "You've already got people watching you. Just like I do. Just like the captain does. Ishida probably keeps a whole squad of them busy, only because of who he is. If you go and make that worse by openly defying the Sōtaichō's standards, you might not like what happens to you. Or the people you love."

She sighed, wrinkling her nose. It went against every instinct she had to try and hide her feelings—about pretty much anything. But Karin could understand that Renji's warning was out of concern for her, not meant to restrict her further.

"It's still fucked up. Besides, if I can figure out that two people I just met are together, wouldn't it be really easy for the Onmitsukidō or whoever?"

Renji shrugged. "Ever heard of an open secret? It's kinda like that. Like I said—if you stay under the radar and do your job the way you're supposed to, people can look past it. There's even a form for officially-recognized fraternization relationships, I think. It's the minute you start letting it interfere with your duties that it becomes a problem."

"This place is so fucking backwards sometimes."

Renji didn't disagree.

When they reached the barracks, he waved her off with a reminder about soccer the next night. Karin, already dreading the stack of forms on her desk, decided it was better to face it now than later. Besides, she wanted to be finished in time for dinner—her future promotion was bound to ensure she had to stay late for dessert while the old man rambled about how proud he was.

Despite herself, she felt her lips twitch into a smile.

Term Dictionary:

Tobase – 飛ばせ – "Fly." One of Hisaku's special techniques. This one gives a boost to Karin's shunpō and other movement techniques, by manipulating the area around her feet with powerful thermal air currents. As a consequence, it also hurts a lot more when she kicks while using this technique.

So there's Karin's daily life, more or less. The next chapter will be about Uryū.