Because the facts that I am a doctor's daughter and Ukitake Juushiro has a chronic illness combine to equal 'me wanting to fix him', anime character or not. You'd think Ichigo (as a doctor's son) would catch on in canon.

Chapter 1

Ichigo was, of course, the only one in his family capable of seeing—and therefore treating—the samurai. He knew she wasn't really a samurai, (lack of daisho* a pretty big giveaway, no matter the fact that she was a spirit) but without anything else to think of her as and no real time for questions, it worked well enough as a descriptor.

He sighed, settling her in a patient's room in the clinic-side of the building while his dad hovered anxiously, then turned with the intent of gathering basic first aid materials—he didn't really know what would work on a spirit, after all.

"Wait here," he told the still-silent woman, "I'll be back in a few minutes. Try not to move around too much—that may not be too deep, but it's pretty wide and I'd rather you didn't restart the bleeding."

Isshin was following him, somber and silent, and that was… kinda creepy, actually.

"Son…"

Ichigo paused, glancing back down the hall to see that his old man had closed the door to the patient room he'd left the injured woman in.

"What happened?"

Ichigo sighed and gave a brief summery as he made his way towards where the medical supplies were kept.

"Not that way," Isshin laid a hand on his shoulder, stopping him. "I-I'd hoped you wouldn't find out about this until… I just wanted you and your sisters to have normal, human lives. But… I owe you an explanation. How badly is the Shinigami girl hurt?"

Shinigami. A name for the type of spirit at last. "Badly enough that it needs to be seen to, but it shouldn't be life-threatening. Although she hit that lamppost pretty hard, so she might have a concussion. It would have killed a human."

"Spirits with power are much more resilient than humans, son. I don't regret what I did for your mother, for our family… but now I wish that the recovery was faster. I can't even see right now; haven't been able to since before you were born. It means Hollows don't hunt me and Shinigami don't notice, but… You were born with power. And power… attracts Hollows."

Isshin sighed, shaking his head, "Still, time for proper explanations later. Now—here."

Isshin opened the door to his own bedroom, slid open the closet, and pulled out a large first-aid kit. "You need bandages made from reishi or imbued with reiyōku* to treat wounds to a spirit. I can't see what's in here anymore, but none of it would have needed to be replaced like human-world items. And… lets just say the afterlife doesn't worry about infections for a reason. Besides, human-world bacteria wouldn't be a problem to Shinigami anyway."

Ichigo nodded, taking the kit. He had a lot to think about.

"Get the basic explanation from the Shinigami girl. I don't want to tell you too much before then, or she'll get suspicious. Right now, I can't afford too much scrutiny."

"Right," Ichigo sighed, glanced at his father. "Well. Get some rest, Oyaji. We can talk tomorrow after school, if you want."

Isshin nodded and Ichigo hesitated with a hand on the doorframe, glancing back. "… You don't have to tell me everything."

Isshin blinked as his son disappeared from his line of sight, huffing a half-laugh. He'd known Ichigo longer than anyone else had, but his son could still surprise him.

xxxx

"... What's your name?" Ichigo asked as he finished securing the bandages around the small Shinigami's torso and tugged black cloth back up to cover them.

"Kuchiki Rukia, Shinigami," she answered after a moment.

"Kurosaki Ichigo," Ichigo let his lips twitch into a wry smile, "high school student."

"… You rejected my power," Rukia murmured, wondering and soft. "That… should have killed us both."

Ichigo shook his head, "Not rejected," he stated, taking a single step back from the bed and tugging out the visitor's chair to sit. "Returned. I… didn't need your power. I have my own. I just hadn't figured out how to use it. You woke it up; that's all I needed."

"You're Shinketsu? A true-born in the Living World? That hasn't happened for centuries."

"I wouldn't know," Ichigo shrugged, rubbing a hand over his face. "I've done what I can, but I don't really know anything about healing spirits. Is there someone anywhere nearby who can help you?"

"I can call for a medic from Fourth," Rukia reached into the black shihakusho she was wearing and pulled out what looked like a standard flip-open cell phone. "I'll need to explain you to them, but Shinketsu are… well. You'll be drawn in to some degree whether you want to be or not, especially with all the Hollows in this town. And, since you don't have any of my power, they won't be able to say anything against you."

"You offered me your power to save lives…" Ichigo said slowly, "… and that's illegal?"

Rukia nodded, face grave. "Even the attempt could get me a few years in prison," she admitted. "If you'd actually taken my power and it had been found out…"

"Let's skip that part in your 'explanation', huh? Just say the Hollow knocked me out of my body, or something. I've certainly heard of out-of-body experiences from near-death often enough."

After a moment, Rukia nodded. "That might be for the best. All right, I'll contact Ukitake-taicho and let him know what's happened. He'll contact the Fourth Division and send a medic. You should probably get looked at, too—even though you're Shinketsu, it had to be hard on your body to be without a soul for so long."

"Fair enough," Ichigo rolled his shoulders, wincing. "I am feeling a bit off. I'll be back in a couple minutes—I need to check on my sisters."

xxxx

Ichigo did check on his sisters, both of whom were sleeping peacefully—probably something his Dad had given them, considering—and slipped further down the hall to knock lightly at his dad's door.

The instant reply was unsurprising.

Ichigo stepped inside, closing the door behind him. "Her name is Kuchiki Rukia—" he cut himself off at the visible wince. "Bad?"

"I don't personally know a 'Rukia', but the Kuchiki are a noble family. One of the Great Houses; someone will be looking for her. If she gave you her power…"

"She didn't," Ichigo cut in, wanting to settle that quickly, "Not that she didn't try, but… something woke inside me and I just… pushed her power back into her blade. She called me 'Shinketsu' and she's calling a captain for a medic. I just thought you should know in case you need to lie low for a while, or something."

"Ah," Isshin visibly thought about that. "That's… probably a good thing. I don't have any power right now, so even if it's someone who knew me, I won't feel the same to them. That's more important than look. And… I'm not the same person anymore. They'll probably think that you got your reiatsu from your mother—you even may have, she had a lot for a human—but I'll stay in here tonight. If they're still around in the morning… well, we'll figure it out. I have a friend who could probably do something to keep them from noticing, even after my power returns. It's… starting to. I could almost see that Plus spirit that was following you earlier. It takes more power to see Shinigami and Hollows."

Ichigo blinked at him, "Well, see you in the morning, then. Rukia said that she wanted the medic to take a look at me, too—something about it being hard on a human body to be without a soul. I'm kinda feeling that."

Isshin made a sound that was only half laugh, "Yeah. That's a good idea. Whenever you're not in your body—it's physically dead*, unless you have a imitation-soul to keep things like, you know, heartbeat and breathing going. I thought… I couldn't see you, and I thought you were dead."

Ichigo winced, "Sorry about that-"

The doorbell rang.

"We'll talk tomorrow. It sounds like the medics are here."

xxxx

Ichigo opened the door to two people wearing white haori over black shihakusho, both wearing single blades sheathed on their left hips. He gave a mental shrug; Rukia wouldn't let her blade be out of easy reach, so it made sense that the others wouldn't either. Considering the way his own blade felt… and he could still feel it, human body or no… yeah. He could empathize with that.

They felt much more powerful than Rukia—when it came to terms of raw reiatsu, still less than what he knew he possessed, but far more refined than his own firm suppression. Something within shifted, a flicker of interest not entirely his own, a shadow of the blade hidden with his soul.

Man and woman, he catalogued absently. The man had white hair a little longer than shoulder-length and a kindly intrigued expression. The woman had long black hair, pulled around both sides of her throat and braided down the front of her shihakusho. Strange style, but it would keep long hair out of the way.

No time to worry on that, not yet. "I take it you're the ones Rukia called?"

Twin blinks, then the man smiled. "Yes, I'm Ukitake Juushiro, Captain of the Thirteenth Division; and this is Unohana Retsu, Captain of the Fourth. Are you Kurosaki Ichigo?"

Ichigo nodded, stepping to the side, "Come in. Rukia's in one of the clinic's overnight single rooms. My family knows I can see spirits, and Dad didn't really want to find out what would happen if someone walked in to see a blanket hanging in the air." He paused, "Granted, we don't usually keep patients overnight, the hospital's better equipped for that, but night-time emergencies happen, and better to be careful."

He closed and locked the front door, "This way."

xxxx

Rukia started to jerk herself upright the moment Ichigo stepped through the door, giving her a look at the white-haired captain behind him.

Ichigo crossed the room and pushed her back with a hand on her good shoulder even as she winced sharply, reaching to press against the bandages covering her wound even as she stuttered out, "U-Ukitake-taicho!"

A quick glance showed spots of blood soaking through white cloth and Ichigo huffed irritably, "What did I tell you about moving? You're bleeding again, idiot," he glanced back at the door, "Oi, Unohana-san? You're a—healer, right? She could use one."

"Unohana-taicho, too?" Rukia blinked in shock, "Why would…?"

Ukitake smiled at her even as he made sure to stay out of the other captain's way, "The entire situation is… a bit unusual. We decided it was best if Retsu-san checked over Kurosaki-kun herself, as none of the others have had to deal with prolonged soul-separation in a human. I think Isane-san is the only other with any experience and she was only called for a situation lasting under forty seconds, and that was with the Chain of Fate still attached."

Chain of Fate? Probably the chains he saw on normal spirits' chests, always broken. So… attached meant alive? The comment implied that his wasn't, but the fact they were calling it 'separation' instead of 'death' meant something. What did that make him?

"Oh," Rukia sighed in relief as the Fourth Captain let the green glow around her hand die out and stepped back.

"That should do it, Kuchiki-san. Still, try to get a good night's rest."

"Hai, Unohana-taicho."

Ukitake smiled, "It's good to see that you're all right. When the Twelfth announced a Hollow with level six reiatsu in Karakura... well, I was concerned for you. Your request for medical aid did not precisely soothe my worries."

Rukia flushed, glancing aside, then blinked and looked back at the white-haired captain. "Level six? That's mid-lieutenant level!"

"You should see about upgrading the trackers you guys use," Ichigo observed, setting aside the dead/alive question for later. "I'm going to assume you guys are mostly ranked by power and skill, right? And reiatsu would be 'power', so… skill notwithstanding, that thing felt maybe half again as powerful as Rukia. And it was fast. So… if those trackers gave you guys information on power level, you'd know when to call backup, right? It would probably save you guys a lot of trouble, if not lives."

"That is… a very good point, Kurosaki-san," Unohana murmured, eyeing the human before her with interest. "I will talk it over with Mayuri-taicho… although he likely would not care about lives, he may take it as a challenge to his professional pride if I word it correctly."

"That aside," Ukitake spoke up, giving Ichigo the same sort of pleasantly intrigued look that Unohana sported, "We should let Rukia-san rest as well as make sure you took no lasting damage from your foray outside your body, Kurosaki-kun."

"Aa," Ichigo moved toward the door, "Sleep well, Rukia," he offered before turning his attention to the two captains, "My room's this way. My little sisters are sleeping, but they probably won't wake up. I think Oyaji gave them something—the Hollow grabbed them, and they were pretty shaken up. Actually… Unohana-san? Could you look them over? Yuzu was unconscious for a while, and human medicine doesn't really have a way to treat mild concussions."

"Sisters?" Ukitake asked even as Unohana nodded with a firm affirmative.

"Yeah," Ichigo tapped once on the twins' door before pushing it open to let Unohana inside, "Karin and Yuzu. They're fraternal twins. Yuzu took over most of the housework since Kaa-san died. Dad's a total spaz; he would never be able to take care of the house and keep clinic records in order… actually, I take that back. Yuzu files most of the paperwork, too. Oyaji's pretty much the least organized person I know. Karin helps out wherever she can."

"Oh? Could we speak with your father?"

"No; he can't see or hear spirits at all. Yuzu can sometimes hear the spirits I usually see around town and Karin can see them, but neither one of them saw that Hollow or Rukia. I'm pretty sure there'd be no point in you trying to talk to Dad."

Ukitake hummed consideringly.

"… Although…" Ichigo hesitated, "Oyaji did say Kaa-san could see ghosts. And… when I was little, I couldn't tell the difference between spirits and people. I would talk to spirits pretty often, and sometimes Kaa-san joined in."

"Then you probably got your high spirit energy from your mother, Kurosaki-san," Unohana stated, emerging from the twins' room. "Both of them will be fine," she added at his questioning glance. "I still need to take a look at you, though, and your hands seem to be trembling."

"Yeah," Ichigo led his way to his room—spartan and neat, as always—and dropped down to sit on his bed. "I've been feeling off ever since I got back in my body, but that's not really a surprise. Normally, it takes days for a human body to sort itself back out after a prolonged period of clinical death. And my heart did stop—Dad was terrified for a minute there."

He got a frown from the healer-captain for that, but he waved his hand dismissively, "My sisters and Rukia were the ones who'd actually been hurt. I just suffered temporary cardiac arrest. Given the circumstances, even without treatment I should be fine. Treatment will just speed up recovery. Give me some credit, Unohana-san, I live in a medical clinic."

Unohana blinked and Ukitake gave a chuckle that devolved into painful-sounding coughing.

The healer turned, visibly concerned, and Ukitake waved at her as he caught his breath, "I'm all right. Check over Kurosaki-kun first."

Ichigo re-ran that short interaction several times, his habitual frown deepening. "Ukitake-san, does that happen often?"

"Hai," the white-haired man smiled, a bit ruefully, "I've had it for most of my life."

"… Do you ever cough blood?"

Unohana didn't hesitate in moving her green-glowing hands over his torso (which was making Ichigo feel a lot better, if he were honest) but her eyes sharpened as she answered for the other Shinigami. "Yes, he does."

"Fever? Loss of appetite while suffering from fevers?"

This time, the healer's hands did pause as Ukitake answered cautiously, "Yes to both."

"Any other common symptoms?"

Ukitake shook his head, "Not really, no. Occasional organ damage, but not ever as bad as my lungs."

Ichigo made a noncommittal hum, thinking. Bacterial, probably, but not bacterial pneumonia…

"Are those… recognized symptoms in the Living World, Kurosaki-san?" Unohana asked carefully, returning to her work.

"Yeah, actually. Long term illness and not dead yet… Hm. How does your healing work?"

"Why do you ask?" Ukitake questioned, noting Unohana's darkening expression and doing his best to avert any blatant disapproval from one of the most terrifying people ever.

"Because it might help me narrow things down. They are pretty widespread symptoms, after all."

With that, the shadow left Unohana's expression, "Simply put, we manipulate reishi in order to convince the body to heal itself from damage."

"Damage… what of illness?"

"There are very few illnesses in Soul Society, Kurosaki-san," Unohana informed. "Most pass quickly when the effects are treated."

Ichigo nodded slowly, "Probably Tuberculosis, then. There aren't a lot of illnesses in the Living World that can't be fought off naturally, given enough time and some way to keep symptoms under control, but there are a few that just… spread. Tuberculosis is one of those—it's a bacterial disease, usually starts in the lungs. Left untreated, it will eventually spread to other organs, if accumulated damage to the lungs doesn't just kill. Sooner or later, scar tissue adds up to suffocation in humans."

"What is this… 'bacterial disease'?"

Ichigo stared for a long moment as Unohana let the green glow peter out before stepping back. "You don't know—all right. Um, they're—uh, hm. How do I explain this? They're… tiny creatures. They're everywhere in the Living World. Most are fairly innocuous, neither helpful nor harmful. Some are helpful—there are quite a few that human bodies actually can't live without. A fair number are harmful—some few are very harmful. Tuberculosis is caused by one of those few. They invade the body, usually through the lungs, and start to feed on them, causing lacerations. Let alone, they multiply and spread and sooner or later start to cause damage to other organs.

"If you have a way to repair damage without leaving scar tissue, it could continue for a long time. The body would naturally try to fight off the infection, but after a while the bacteria would become resistant to natural antibodies and start to spread faster. If you're only treating the effects and not the disease… Well. Sooner or later, it'll turn fatal."

"Do you have a way to cure it?" Unohana's voice was intent, eyes almost desperately pleading.

"Yeah. We have a wide range of antibiotics that'll take out bacteria, but you should probably have it tested first. Each strain needs to be handled differently, and the wrong antibiotic could even make things worse. And I'm not even sure it would work on a spirit—"

"We have false bodies we can use to interact with humans. Do you think…?"

"False… bodies? If the bacteria were forced into a physical body… that might work. Otherwise… huh. Antibiotics are basically poisons that effect bacteria but not humans, and if I tried flooding one of the normal treatments with reiyōku, it might make it work either way. Um… I'd need a blood sample to test that, though. If you get yourself a false body and get me a blood sample from your normal form, I can talk to my dad about picking up the right kind of antibiotics. It'll take a few days—the hospital likes paperwork—but the sooner you get back, the sooner we can get started."

Unohana stepped forward and wrapped Ichigo in a tight hug, much to the human's consternation. "Thank you."

"I still don't know if it'll work," Ichigo cautioned as the woman drew back.

"No, but… it's a new direction. If this doesn't work, we can set the Twelfth on it. Either way… it's the best news we've had in years."

Ichigo glanced at the stunned-to-silence Ukitake and dipped his head, "You're welcome, then."

xxxx

"I was going to explain—as Shinketsu, you will need to know, regardless of your current state as a living human."

Ichigo waved him off, "Rukia's assigned to Karakura for now, I can ask her if anything immediate comes up. You're coming back soon, anyway, right? It can wait a while."

Ukitake smiled, small and genuine. "Very well. And… thank you."

Rice-paper doors slid shut and faded.

Ichigo made his way back inside, collapsing into bed for what little sleep he'd be able to manage before morning.

xxxx

Daisho: Paired swords. Katana and wakizashi together were worn by samurai only partly for actual use. They were also used as a badge of office; the mark of the feudal Japanese equivalent of European knights. Both had to be both nobility and warriors.

Reishi: Spirit particles

Reiyōku: Spirit energy/power

physically dead: I'm not sure it's ever directly addressed in Canon, but the implication is that a normal soul's Chain of Fate indicates whether the body is alive or dead while in the Living World. A broken Chain means 'dead', obviously, while one still attached to the body means 'alive'. Shinigami, by definition, are not normal souls and do not possess Chains of Fate. Gigai, being false bodies and never alive to begin with, are completely dormant without some kind of driving force, whether Shinigami or Gikon. (Or Mod-Soul, as the case may be.)

Missing the Chain that should have been binding it to its soul, my belief is that Ichigo's body would also completely shut down without him inside it. And when the heart stops beating, bodies undergo quite a few detrimental changes that—even if the person is revived—usually have at least short-term consequences. (Can you tell my dad was a doctor? He's retired, but the things you learn from the guy who used to do the autopsies is… kinda morbidly interesting, if I'm honest.) Obviously, none of that is addressed in Cannon, but this is where my thought-train goes.