Disclaimer: Still don't own anything to do with Bleach.

This is part of the Chaos Theory AU. Like the other works in the series, it's best understood after reading at least The Butterfly Effect and The Three-Body Problem. It contains my revisionary take on Bleach: The Hell Verse, which was a movie with a surprising amount of potential that imho kinda went to waste. I'm changing it... well, a lot.

Be advised that some of the descriptions herein may be somewhat disturbing. It is, after all, Hell.

The Uncertainty Principle

A Bleach Fanfic

Chapter One: Conquest

"The truly creative mind in any field is no more than this: A human creature born
abnormally, inhumanly sensitive. To him... a touch is a blow, a sound is a noise, a
misfortune is a tragedy, a joy is an ecstasy, a friend is a lover, a lover is a god, and failure is
death. Add to this cruelly delicate organism the overpowering necessity to create, create,
create—so that without the creating of music or poetry or books or buildings or something
of meaning, his very breath is cut off from him. He must create, must pour out creation. By
some strange, unknown, inward urgency he is not really alive unless he is creating."

― Pearl S. Buck

The ground beneath his feet had the consistency of sand, or thereabouts; he'd have to study it a little more closely to be certain, but he suspected it was made primarily of crushed bones.

Has it been created thus, or was there some layer of something else beneath? Did Hell have soil horizons? Bedrock? He had the means to find out; what he lacked, really, was the opportunity.

Kisuke was aware that the Togabito in front of him were still speaking, but he took in their words only distantly. Conversation wasn't really a drain on his intellectual resources; he rarely wasted much more energy on it than strictly necessary. They were only trying to manipulate him into doing something for them in return for the information he wanted, anyway. As he had no intention of breaking any chains, theirs or otherwise, it was much more productive to let them exhaust themselves laying out their case, and spend the time doing other things.

He shouldn't be worrying about the sediment though; there were too many other things to occupy him before that would have any kind of priority. That was the worst thing about wars, honestly—so much effort went into winning them. If winning was really an applicable word. Kisuke tended to think of it as losing less badly than whoever else was involved.

The essence of victory really came down in cases like this to nothing but planning better; that came down to some combination of knowing more and being smarter, which most people conflated.

Most people were not capable of the requisite combination, unsurprisingly.

"Will you do it?"

Ah. Something in need of an answer. Kisuke smiled, the left side of his mouth lifting higher than the right. From the shade of his hat, he fixed his eyes on the leader. Not the one in the front, doing most of the talking—the one nearer the back, who hadn't stopped staring at him the whole time. The only one who might have noticed that the majority of his attention had been elsewhere for the duration.

"I'm not really in the habit of giving something for nothing," he replied in the sly tone he knew they'd hate.

The one in the front bristled. "What do you mean, nothing? If you free us, we'll give you all the information you need."

"See, I think we're having a misunderstanding, here," Kisuke continued blithely. "You're under the impression that I believe you, which I don't. What we both know, actually, is that you don't have what I'm looking for. So, if you don't mind, I think I'm just going to wander around for a while."

"Why you—" One of the others didn't seem inclined to talk so much as attack. But that was fine—it might actually end things faster.

He surged forward, tentacles emerging from under his ratty black robe and rushing at Kisuke.

There were so many one-liners to be had. Unfortunately, his wit was completely wasted on these people. Sighing, Kisuke drew Benihime from his cane in a lazy motion, flicking the blade in a sharp arc that sliced directly through the left-side tentacle. The right one was trying to wrap around him from behind.

"I don't think we've quite reached the hug-it-out point in our relationship," he quipped.

Keeping himself planted on the ground, Kisuke caught the incoming tentacle and lashed with his arm, the momentum passing through the connection and lifting the Togabito from his feet. He slammed sideways into one of the others, who'd only just decided to enter the fight. Really. That was a pretty slow decision, even for one of them.

He let go of the tentacle and sighed, arching an eyebrow at the other two—the leader and the girthy one. "We can dance, if you really want to, but you're smart enough to know how this ends. So I'm going to back through those gates, close them behind me—and then we're all going to act like this never happened, all right?"

His hospitable smile was met with silence, but none of them attacked again, so he did as he'd said. Getting back up to the gates wasn't really a problem with shunpō. When he stepped through them into his basement, they closed behind him; he re-sealed them with kidō, but did not banish them.

He still, after all, needed that information. Togabito weren't able to exit the gates, but it was better for the living world if he didn't leave them hanging open for too long. Sheathing Benihime, he frowned at the slime on his free hand. Well, at least he could take a culture of it—it might go some way to confirming some hypotheses he had about the Togabito in general.

The living room was quiet. Tessai and the kids had left after dinner concluded a few minutes ago—leaving Kisuke and Yoruichi. She was presently cat-shaped, which she knew amused him.

"You went into Hell again." It wasn't a question.

He didn't treat it like one. Draining the remnants of his teacup, Kisuke set it down on the table. "Just the first level, still. I'll have to go further if I want the answers." He tapped his fingers on his knee.

Yoruichi had some idea of the way his mind worked, though she couldn't pretend she understood it completely. What she did know was that the particular look on his face now meant he'd gone somewhere she could not follow. He had always been like that—though it had been worse when they were kids. Before he'd had anything else but his thoughts.

Without the right kind of face to frown, Yoruichi channeled her displeasure into lashing her tail. "I don't like this idea, Kisuke. We're meddling in things we don't fully understand."

His eyes, deeply into the middle distance, cleared at the sound of her voice. He blinked at her, tipping his head back. "Yet," he replied.

With him, that word carried weight.

But that didn't mean she had to like this. "But Hell? You're sure we can't do this some other way?"

He half-smiled at her, an almost-perplexed look on his face. "Of course I'm not sure. That's why I'm looking into everything—you know that."

Yoruichi hopped up onto the table, padding over to the edge of it to sit directly in front of him. When she looked up at his face from this angle, the attempts he made to conceal his eyes were moot. "What are you really doing?" she asked quietly. "This isn't just about binding kidō."

He took one of his hands from inside the opposite sleeve and laid it on her head. Calloused fingertips wrapped around behind her ears—Yoruichi leaned into the touch. No matter how much practice she had being a cat, some things about it would just never resemble being humanoid.

"No," he confessed. "It isn't."

Yoruichi had noticed long ago that there was a specific range of tones he reserved for use when he wasn't pretending. One of them was this one—soft, slightly raspy, and tentative, in a way that he never allowed himself to be around others. With three words, she understood that his reservations were as many as hers, but that he would proceed anyway. Because he'd calculated the chance of something useful coming out of this to be high enough to justify the risk.

She also knew he wasn't planning on sharing with her just yet what the rest of it was about.

Inwardly grimacing, Yoruichi sighed. Gathering her legs under her, she hopped upwards and landed on his shoulder, draping herself around his neck.

"Fine then. But you'll have to tell me eventually."

Kisuke had never actually been that fond of the color red.

So perhaps it was fitting that his entire inner world was in shades of it, from dull brown-red to bright scarlet and every gradation in between.

He had landed, this time, in the very center of it—Benihime's throne room. It was a rather gruesome place, in truth. The floor of it was red wood, the shape a long rectangle with a dais at the far end, where she sat in perfect seiza, lips painted carbuncle and hair black as night. Her castle had no ceiling; rather, it was open to the sky above, the blood moon low in the sky directly overhead. Everything was cast in the eerie pall of it, including the both of them. What walls and roofs the castle had left were skeletal, solid at the bottom and liquid-jagged at the top—as though at some point, blood had run upwards and half-completed the outline.

Behind him, the doors to the hall stood open, revealing that the entire edifice sat on a lake of red water, stretching in all directions for as far as the eye could see. The hall was adorned with rich tapestries and artwork, all sharing the monochromatic theme.

The spirit herself was a beautiful woman, something that had amused him when he discovered her. But her body was not a human's—it had ball-and-socket joints, like a marionette; the cut ends of her strings bled behind her in crimson ribbons. She rarely spoke to him for any reason but to criticize; Kisuke didn't really mind.

He used Jinzen more often to organize his thoughts than to talk to her anyway.

Turning to the left, he wandered over to one of the tapestries. This one, he had unwound and rewoven for his own purposes, and it displayed now a visual matrix that represented all of the plans he had in motion. It was the most complex such map he had ever created—but the situation demanded that. Kisuke planned first from his opponent's options, and Aizen had many. Not to mention the ingenuity to create many more. The number of possibilities regarding upcoming events was staggering; and, at this stage, the number he could safely eliminate was few.

So the ideal response was to craft his own countermeasures in such a way as to cover as many possibilities as he could. A tactic with several applications was, all other things equal, better than a tactic with only one, no matter how sublimely it would accomplish the single purpose. But overgeneralizing carried its own risks as well—everything was a delicate balance.

Kisuke ran his fingertip along a particular red thread, split into many and anchoring one corner of the fabric. The rough skin dragged and caught slightly against the impossible smoothness of the silk. Aizen and his Arrancar. He traced another with his thumb, turning it blue with a thought. The Visored. Gold; braided. Soul Society. Foggy grey, thin. Perhaps even a few of the local humans, though that possibility diminished at this point. Green, purple, orange. Himself, Yoruichi, and Tessai. Black. White. Isshin. Ryūken. And, of course, silverbright Uryū.

A direct assault. Sabotage from within. Diversion and ambush. A lightning offensive or a drawn-out siege. Each offered dozens of pros and cons, for both Aizen and himself. Each remained viable. The one thing he'd been able to determine to a reasonable degree of certainty was Aizen's final aim, and the means he intended to use.

He wanted to create an Ōken, enter the Soul King's dimension, and kill it.

There was no doubt whatsoever in Kisuke's mind that he was the person Aizen ultimately considered his opponent. He had not cast it in such terms when he rebelled, of course. But by now, he knew. They both did—even if no one else had seen it yet.

Armies would clash. People would die. Threads would snap and tangle and intersect anew.

But in the end, it would come down to what it always did: which one of them had planned better. Which one of them could think faster, when their plans inevitably began to disintegrate.

Which of them had the art refined to the point of quintessence.

Which of them made the stronger, tighter weave.

"He has more resources," Benihime said suddenly.

For a long moment, he did not answer her.

"Yes," he agreed at last. Turning his head from the tapestry, he blinked at the frown she wore. "But I'm smarter than he is."

"Will that make a difference, when he figures out how to meld the Hōgyoku with his body?" She looked down her nose at him—he could tell, even from this distance.

"I don't know," he admitted with a slow grin.

"But won't it be interesting to find out?"

Yoruichi sprawled on her back, arms flung out to either side. Though it was well past reasonable sleeping hours, she found she couldn't quiet her mind enough to do more than doze. It wasn't often that happened to her—but there were people who could be troublesome enough to worry her to such a state.

She blew out a breath, disturbing the strand of hair in front of her face. When it fell back into her eyes, she reached up and ran her fingers through it, tugging it back to lay with the rest. Rolling her head to the side, she stared out the window. There was a bit of glare from a street lamp, but other than that, she had a patch of night sky to look at and not much else.

Folding her hands behind her head, she rested back on them. She wondered what Ishida was up to. She always did tend to develop an attachment to the ridiculously-stubborn ones. Kisuke, Suì-Fēng—even Kūkaku and Isshin had their moments. Maybe it was because they were too much fun to tease…

A small sound drew Yoruichi's attention; she narrowed her eyes. Kisuke was asleep—she knew because she'd bodily shoved him into his bedroom before he spent another night working on something in the basement. Tessai might still be up with the kids, but—

This time, the noise was accompanied by a small tremor in the floor; Yoruichi sat up, brow furrowing. When she heard Tessai shout, she immediately bolted out the door. Kisuke was already in the hallway as well, cane in one hand. They took one look at each other and flashed down the stairs.

"Basement," he said, his tone urgent.

By the time they reached the basement landing, the problem had become glaringly-obvious: Tessai looked to be unconscious, bleeding heavily from a massive slash wound across his chest. That was bad enough—but the even bigger problem was that the Gates to Hell were standing open.

And the two who'd come through them were each holding one of the kids.

They were robed and masked—it was impossible to make out any distinguishing features. And of course the basement masked their reiatsu to anyone outside or upstairs. Yoruichi gritted her teeth. They were holding blades to Ururu and Jinta's necks—both of the children were unresponsive.

"Kisuke Urahara," said the one holding Ururu. "You're… what was it? Smart enough to know how this ends? Don't draw your sword, don't take so much as another step, or I'll slit her throat."

Yoruichi didn't take her eyes off them, but she could feel Kisuke shifting. This was—she didn't know a word bad enough for this. These guys had enough reiatsu to make good on it. Even she wasn't fast enough to get over there and disarm them before they managed to kill one or both of the kids.

Trying anyway simply wasn't an option.

"You want me to cut your chains that badly, huh?" Kisuke's voice indicated none of his prior concern; it was as nonchalant and slightly-amused as it ever was.

Well, she supposed it must sound like that to them, anyway. Yoruichi knew better.

"Precisely. Here's how this is going to work. We're taking these two back with us. You're going to follow us. After that, we're going to resume this negotiation in the Final Circle. I suggest you prepare yourself to remove our chains, but don't wait too long, or the little ones here will have chains of their own."

Before either of them could so much as counteroffer, the two cloaked figures jumped back into the gate. Kisuke flashed after them, but they were gone by the time he reached the threshold.

Yoruichi, throat tight, moved to stand beside him. He was still disheveled from rolling out of bed, without either his hat or overcoat in evidence. Bereft of his armor, he looked so much more like the boy she'd known once—when she herself was still only a girl.

"That wasn't supposed to be possible," he said slowly. It was as though he was still trying to make sense of it. "The laws of Hell are—" he clamped his mouth shut, shaking his head.

"Useless. Laws. I break laws all the time. Impossible is for idiots. I should have predicted this. Should have—"

"Kisuke." Yoruichi tugged sharply on his sleeve. "Stop. Focus. We need to get the kids back. How do we do that?"

He pulled in a breath and held it. Yoruichi waited patiently for him to reset his thoughts, but her skin itched with the need to act. Ururu and Jinta… imagining them in Hell was damn near terrifying. Her fingers tightened in his sleeve; she may have put them there for his sake, but she kept them there for her own.

Kisuke ran a hand through his hair. "Physically cutting the chains is easy. Predicting the results was the part I hadn't figured out yet." His mouth dropped into a frown. "Yoruichi. I need you to get a message through to Soul Society. Ukitake. Tell him as much as you need to to get Uryū here. And at least two other reliable people. I have an idea, but they have to be willing to go through with it."

"What are we going to be doing?"

He smiled; she ignored the way it trembled at the edges.

"We're making a trip into Hell, of course."

They arrived in Karakura town under cover of darkness.

Considering he'd been a seated officer in a Gotei 13 squad for nearly eighteen months, it was not Uryū's first foray back into the living world. He'd led squads for Hollow neutralization purposes before. But this did mark the first occasion on which he'd been sent back to the place of his birth.

Perhaps more odd than this fact, however, was the part where it was all very unofficial. As the captain in charge of the Thirteenth, Ukitake-taichō had jurisdiction over Karakura, and the authority to send any of his own squad to check on it for whatever reason he liked. As someone with other captains for friends, he was able to impose upon them to borrow some of their squad members as well. That was exceedingly rare, but not unheard-of.

None of that quite fully explained this combination of choices. Uryū slowed his descent to the ground with shunpō, landing softly. Behind him followed Rukia, then Renji and Karin after. The four exchanged glances.

Nothing was immediately off. Ukitake had indicated that they should meet up with Urahara, but had not described the nature of the problem any more specifically than that. Uryū sensed no Hollows or similar disturbances. The night itself was quiet, only a few lights on in the windows of the houses on the street.

"It's this way," he said, starting forward.

The trip to Urahara's shop took them scant moments with shunpō. Uryū regarded the edifice with a hint of nostalgia before stepping forward and knocking briefly at the door.

Yoruichi answered, which was unusual. More unusual was the look on her face—she wasn't smiling, or even amused. Rather, her mouth was set into a frown; though she reached forward and gripped his shoulder by way of greeting, it was too soon gone in favor of showing all of them in.

Immediately suspicious, Uryū counted the reiatsu signatures in the shop. Tessai's was weaker than he remembered it—had Urahara upgraded their gigai? He couldn't sense Ururu or Jinta at all.

"He's in the basement."

Yoruichi led them down. Upon emerging into the familiar training ring, Uryū's eyes automatically found the thing that was out of place. Freestanding in the middle of the room was what looked like a pair of doors, sealed shut. From each protruded the upper half of a skeleton, like macabre doormen—their skulls were bandaged so as to hide one empty eye socket, their visible arms crossed over their ribcages as though they might at any moment use them to pull open the portal.

The entire structure was wrapped in chains, glowing a soft red.

"Kidō chains," Rukia murmured. "But this is…"

"Jigoku no Mon."

Urahara spoke from behind them, and the quartet whipped around to see him leaning heavily against one of the basement's rocky outcroppings. His arms were crossed into his sleeves; the brim of his hat pulled low over his eyes.

"You have a Gate here?" Renji sounded like he didn't quite believe it. He glanced back over his shoulder at the doors and swallowed audibly.

"Wait, wait. Back up. Did you just say Jigoku? This thing leads to Hell?" Karin crossed her arms over her chest. "Pretty sure that's supposed to be kind of a no-go for us shinigami, right?"

"Second dictum," Uryū confirmed. He still didn't remove his eyes from Urahara. If they were called here and it had something to do with this… he didn't like where it was going.

Urahara met his eyes, the look in his somehow indecipherable. "Generally speaking, yes. But when we're staring down a war where the enemy has a complete Hōgyoku… well, I'm not really a shinigami anymore, am I?" He lifted his shoulders, still affecting the same casual confidence he always did.

"What are we here for?" Uryū still didn't like it. "You didn't drag us all the way out here to show us this."

Urahara nodded. "I didn't. Actually… you're here because I need your help. You see…" he trailed off—Uryū wondered if he was imagining the way the other man's shoulders slumped. "I've made a miscalculation."

"Miscalculation?" Ishida's voice was low and cold.

Rukia couldn't blame him.

"That's what you call this? How could you possibly leave these gates down here if there was even a tiny risk of something coming out of them? They're children."

Urahara shook his head. "I made an error. Everything I've ever read about Hell indicated that nothing makes it out of there without the express permission of the King of Hell."

Rukia had never heard of such a being. But then… Hell wasn't exactly on the Shin'ō curriculum. All anyone ever learned about it was that it was the place that Hollows went when they'd committed unforgivable sins prior to becoming a Hollow—sins that shinigami could therefore not purify. Some people thought that any soul wicked enough went there after death instead of Soul Society, but even that wasn't confirmed.

Still… it surprised her more that Urahara had been wrong than that he apparently knew much more than anyone else did about the topic. The latter was more or less normal.

"So, if I understand you correctly, you based your risk assessment on the assumption that the someone called the King of Hell would not condone the kidnap of children to further his ends?" Ishida's tone was incredulous, still edged with hard anger.

Rukia's hands clenched at her knees; she shifted in her seiza. She remembered Ururu and Jinta—remembered that Ishida had lived with them for a year, and known them before that. His anger was, from her point of view, completely understandable. Even she was… her fingers tightened.

Urahara had dropped his blasé demeanor, either unwilling or unable to keep playing at it in the course of his explanation. But in its place, he wasn't displaying much at all. Rukia couldn't even tell if he regretted it. Those children lived with him; shouldn't he be more upset that they were gone?

"Yes." The reply was uninflected.

Ishida's eyes narrowed; he stood up abruptly. "That's unbelievable, even from you, Urahara-san." His gaze slid to her for a moment.

Rukia knew exactly why. The last time Urahara had displayed this little regard for someone else's risk, it had been hers. But she'd been a stranger—something was still wrong here.

"We're not done here, but there's no time." Ishida expelled a gust of air from his nose. "We're going in, yes?"

Urahara closed his eyes for a moment, nodding his head before he opened them again. "I am. But even I don't know what's down there."

"Then I'm going with you." Ishida's tone left no room for doubt.

Rukia considered the second dictum for all of half a second before she stood, too. "As am I."

Ishida had broken the rules for her when it counted. She could do no less for him.

They turned to the others. "You don't have to do this—" Ishida started.

Karin cut him off with the wave of a hand. "Like I'm gonna let you do this without me." She caught Ishida's eyes and held them. "Don't even think of stopping me."

He dipped his chin tersely.

Renji sighed. "Man. We're gonna get fried for this, aren't we? I'll be lucky if I'm teaching classes for the rest of my natural life."

"Might be kind of a short life," Karin replied, "once they find out about this."

Rukia winced. "Technically, Soul Society doesn't have to know, right? Ukitake-taichō sent us here to meet Urahara-san. Not to do anything in particular."

"We'll cross that bridge when we get to it," Renji said. "For now… I think we have work to do."

"Excellent," Urahara said, rising as well.

Rukia had no doubt at all that he'd predicted more or less this exact course of events. He'd probably requested exactly the people most likely to actually help him. But, considering why he needed the help, she couldn't blame him. Not for that, anyway.

"Get whatever you need, and meet back here in ten minutes."

"You're damn lucky this time, Kisuke," Yoruichi said, crossing her arms and leaning against his doorframe.

He'd retreated to his room to gather whatever he thought he was going to need for the trip. Since she didn't need to take anything with her, she'd simply followed him instead. Tessai was resting in his own room—he wasn't in much shape to be moving around, but he'd be fine in a couple of days, when the healing they'd done ran its course.

Kisuke didn't answer. When he turned back to face her, though, the pretense of calm he'd worn around the others was stripped from his face. Yoruichi could read in his eyes something that she hadn't seen there in a very long time.

It was fear.

She swallowed; her mouth was suddenly dry. Kisuke didn't feel mundane things like fear. Not anymore. Not after everything.

Or maybe… maybe he'd just stopped showing it to her, and she'd forgotten how to look.

"We're going to succeed," she said, talking when his silence became too weighty. She couldn't stand that look on him. It wasn't right. "We're going to get them back."

"Yoruichi," he rasped.

She closed her mouth with a snap.

"I need you to stay here."

"What?" Her whole body went rigid. "You can't possibly—" she was cut off when his hands landed unexpectedly on her shoulders.

"Please."

Her eyes rounded. "Kisuke—"

He shook his head. "Someone has to look after Tessai, and… the Gotei 13 will be here soon. They're going to want to close the Gate behind us. You have to convince them not to, and… stop anything from getting out."

He was right—those things had to be done. They would require someone strong to accomplish. Someone who could not simply be ordered into compliance. Someone to watch their backs. It was vital. Necessary. And she was the best choice for it.

"That's not the reason you want me here," she accused, unable to make herself sound as angry as she wanted to.

"No," he admitted. "But it's a good reason."

Kisuke lowered his head, sliding one of his hands from her shoulder to her arm and pressing his brow into the spot where it had been. Yoruichi closed her eyes. She could feel him trembling. Her chest ached. Raising her free arm, she slid her fingers into his hair, cradling the back of his head to her shoulder.

"We were never going to die peacefully, were we?" she said. A fragment of an old conversation, from a lifetime ago.

"Never," he replied hollowly.

"Bring them back, Kisuke. All of them."

He nodded against her shoulder. When he straightened a few seconds later, he'd wiped the hints of fear and uncertainty from his face and replaced them with the usual crooked smile. "Who do you think you're talking to? I've already got a dozen ways to do it in mind. Just keep Soul Society from interfering too much, and everything will be fine."

An expectant silence hung in the air for several slow seconds, but neither of them filled it. Yoruichi bit her tongue, holding it until after he'd nodded and slid the door open, heading back to the basement.

Only then did she speak.

"And bring yourself back, too."

Term Dictionary:

Togabito – 咎人 – "Offenders." The word has the connotation of "sinners." These are the souls that occupy Hell. It is known that they include purified Hollows whose crimes in life were too great to permit entrance into Soul Society. Rukia (correctly) believes that anyone, Hollow or not, who committed unforgivable offenses in life is consigned to this dimension upon death.

Ōken – 王鍵 – "King's Key." A key that allows passage into the special dimension where the Soul King resides. Aizen is after one.

Jigoku no Mon – 地獄の門 – "Gate(s) of Hell." Pretty self-explanatory. Their appearance differs between actual manga canon and the Hell Verse movie; I went with the former.

So… this is chapter one, which should really be subtitled "Even geniuses screw it up sometimes."

I'm aware that Urahara and Yoruichi (to a lesser extent) are acting a little different from how we see them in canon. But, well… they're in a stressful situation where people they personally care about who can't fight that well are in danger, and… in lots of these scenes, they're only with each other, and you show your best friend sides of yourself you'd never show people who need to believe you're in control of the situation. So there's that.