Chapter 172: Kurosaki Hospital
In truth, Mayuri Kurotsuchi was an outstanding research talent.
His inventions often looked unreliable at first glance, even grotesque, yet they were brutally practical. Each device carried a clear purpose, and Mayuri understood exactly how it would behave in real use.
The spirit particle sealing band on Aizen's wrist was the same.
Mayuri had built it with a threshold. In ordinary combat, Aizen could only exert the strength of an average squad member. Captain level power was sealed, not erased. If a genuine crisis occurred, the spiritual energy surging from Aizen's wrist would shatter the restraint. At the same time, the Research and Development Bureau would receive an immediate alert that Aizen had begun using captain level power, which would trigger the next phase of Mayuri's plan.
To Mayuri, that was not cruelty. It was simply good design.
Room Forty Six needed their authority to stop being challenged, and Mayuri wanted his technology to be universally recognized, unquestioned, worshipped. In fact, Room Forty Six and Mayuri were not perfectly aligned on the details of monitoring Aizen's power, but Mayuri's confidence was absolute. If he claimed he could seal Aizen, then no one else was allowed to interfere with that sealing process. Not again.
Even during the Thousand Year Blood War, Mayuri kept this obsessive research philosophy, even at the edge of catastrophe. It was both his strength and his weakness.
Functionally speaking, even Urahara's astonishing tools were only comparable to Mayuri's. The difference was temperament.
The man in wooden sandals, smiling behind a fan, shared something with Shunsui. If a method worked, then children, adults, captains, even former friends could become pieces on the board. When Ichigo was not obedient, Urahara's so called warnings were not jokes. Urahara did not joke about life and death. If it came to a true line he would kill without hesitation.
Mayuri, on the other hand, could laugh while stepping over corpses.
Among researchers, Mayuri was easier to deal with. A small provocation could make him hand you a surveillance system he believed to be perfect, even if it contained flaws you could exploit.
And for Aizen now, with chakra in his grasp, flaws were no longer a problem.
"No contact points, no intelligence, only one way communication with Soul Society. How stingy of you, Captain Kurotsuchi."
Aizen stepped out of the portal and frowned down at Karakura Town.
Just as he had predicted, Mayuri had been driven nearly insane with anger. With only an hour, that mad researcher had frantically stacked monitoring devices and sealing measures on top of each other, pulling half a laboratory's worth of restraints into the field.
All of it was backed by Room Forty Six.
These sealing items were powerful enough that even Yamamoto Genryusai Shigekuni would treat them seriously. Now they were being used on Aizen, compressing his spiritual energy fluctuations to the level of an ordinary squad member, weaker even than many seated officers.
Shinigami battles were battles of spiritual pressure. The stronger the pressure, the more the enemy was crushed before techniques even mattered. In Mayuri's logic, the seal was nearly perfect. Aizen's spiritual organs were restrained, his output locked down, his presence forced into something small and harmless.
Then they assigned him to guard Karakura Town, to stand by as a reserve force until Seireitei declared the emergency over.
Everyone knew it was a lie. Room Forty Six and the Technology Development Bureau simply wanted to humiliate him. In Seireitei, that was normal.
But for Aizen, escaping a perfect seal was not difficult.
Standing in midair, the spiritual particles and spiritual power within him condensed into a second figure, wearing the Fifth Division haori, glasses, gentle expression, everything precise. The original spiritual self of this world had not fused directly with him. It had been kept as a resource, waiting for the right moment.
That moment was now.
Like slipping a glove onto someone else's hand, the entire set of seals transferred cleanly onto the Shinigami double. The clone's spiritual pressure plunged instantly, dropping to a level that was probably even weaker than Rukia Kuchiki's.
And that was exactly what Mayuri wanted.
Chakra, and the technique of shadow clones, made the substitution seamless.
In some ways, chakra was even more adaptable than the Hogyoku. Drawn from life itself, it could shift, distort, and evolve with will, becoming the state the user envisioned. Aizen and the sealed Shinigami double exchanged a small smile, then split toward separate destinations.
The clone would endure Mayuri's demands and the petty experiments Room Forty Six wanted to force on him, playing the obedient piece.
The real Aizen had only one destination.
He adjusted a perfectly tailored suit and straightened his tie. The smile that appeared on his face was flawless, so natural that even a test of blood and bone would find nothing strange. Then he looked down at the two girls in front of him.
"Good afternoon, children. Is Dr. Kurosaki Isshin still here?"
Karin Kurosaki stared at him with open suspicion.
"If you're looking for our dad, the hospital's right there. Why don't you just go inside?"
Yuzu Kurosaki tugged her sister's sleeve.
"Karin, don't talk like that. You should be polite."
"But don't you think his way of talking is weird?" Karin muttered, still not lowering her guard.
Aizen gave them a kind smile.
In truth, these two girls were backup options, born with a blend of Shinigami and Quincy potential. Their spiritual power would naturally grow to an impressive level with age. In the human world, mediums who could perceive Hollows and Shinigami were rare. Their souls were almost always tied to Shinigami or Quincy bloodlines.
Talent wise, Karin and Yuzu were not far from Ichigo.
Personality was different. Ichigo moved through life with a single instinct, protect others, even at the cost of himself. Karin and Yuzu were not the same kind of blade.
But circumstance shaped people.
If Ichigo were in danger, Yuzu would sacrifice herself without hesitation. Karin would do the same. That much was certain.
Seeing their wariness, Aizen softened his voice.
"I apologize. My wording was awkward."
He glanced at Kurosaki Hospital across the street, then back at the two girls who barely reached his waist.
"To be precise, I've known Dr. Kurosaki for many years. I was recently transferred here, and I wondered if it might be awkward to visit him so suddenly. But I didn't expect that impulsive Kurosaki would have two daughters this adorable. It's honestly astonishing."
Karin's expression twitched.
"Hah, yeah, that does sound like him."
Yuzu sighed, as if forced to agree.
"…There's no denying it."
As they thought of their father's strange behavior, their tension loosened. The faint repulsion around the hospital, the invisible sense of rejection that had been watching Aizen, quietly dissipated.
After Masaki's death, Isshin regained his Shinigami power and developed an intense need to protect his three children. Kurosaki Hospital looked ordinary, but as the home that sheltered his greatest treasures, it could never be unguarded.
There were surveillance devices nearby, including one originally tied to Aizen's own arrangements.
Passive spirit particle detection did not react to chakra, because chakra was not spirit particles at all. The girls themselves opened the door. No alarms sounded. The detectors that measured fear or tension in children showed no spikes.
To ordinary people, the sealing formations were meaningless.
And beyond that, Ichigo's entire development had always existed inside Aizen's broader plan. In some ways, Aizen knew Kurosaki Hospital better than Isshin did.
So he followed behind the two girls as if he belonged there.
They pushed the door open and called inside.
"Dad, your old friend came to see you!"
A lively middle aged voice answered from deeper in the clinic.
"Yes, yes, yes!"
A tall figure sprang out as if launched by a hidden spring.
"This is Kurosaki, Dr. Kurosaki of Karakura Town. Can I help you with anything? But I don't remember knowing anyone here…"
He froze mid performance the instant he saw Aizen.
Aizen chuckled and pushed up his glasses.
"Good afternoon, Dr. Kurosaki. It's been a long time."
Isshin's expression hardened by degrees, the joke face dropping away like a mask being pulled off.
Aizen's tone remained warm, almost friendly.
"It has been quite a while since we last parted ways. This time, I have plenty of time to catch up, and I'm looking forward to it, Kurosaki Isshin. As neighbors who may get along well in the future, I remember there's a custom of bringing a small souvenir."
He took out a small box and placed it on the counter.
"I bought it from a well known dessert shop. They make delicate sweets. It should be a good gift for children."
Isshin's gaze flicked to the box, then to his daughters.
"Karin, Yuzu. Go back to your rooms."
"Huh?" Karin stiffened.
Yuzu blinked, confused.
Their father was not acting crazy. He stood between them and the elegant man at the door, body angled like a wall. A heavy atmosphere settled into the room, making even the children's instincts sharpen.
Then, only seconds later, Isshin forced a laugh and scratched the back of his head as if nothing was wrong.
"Dad and this uncle are old friends who haven't seen each other in a long time. Old men need a drink. You two close the shop first, we're going out."
"Hey, the keys," Karin protested. "You didn't give us the keys."
"They're on the table in the back room," Isshin said quickly.
He pushed Aizen's shoulder as if they were close companions, then shut the door of Kurosaki Hospital.
The roller shutter slammed down, locking with a harsh finality.
Under the setting sun, Isshin separated his daughters from the place that represented his normal life.
He stared at the blood red sky and exhaled slowly.
Once, he had been the captain of the Tenth Division. Once, he had been Shiba Isshin, heir of a branch line tied to one of the great noble houses, a man who knew secret techniques and stood at captain level.
Now he lived inside a special artificial body, his Shinigami power bound by love.
If Ichigo ever awakened the Hollow within him and severed that link, Isshin might regain enough strength to stand against Sosuke Aizen.
But not yet.
Right now, he had no spirit particles to draw on. He could craft tools, yes, but fighting Aizen would be nothing but wishful thinking.
They walked until the streets thinned, then arrived at a small, quiet park. Isshin lit a cigarette and looked at Aizen with cold indifference.
"…What exactly are you here for? To wipe them all out?"
"How could that be?" Aizen replied mildly. "You should know I'm even more concerned for Ichigo Kurosaki's safety than you are."
He sounded sincere, which only made it worse.
"After all, he was hope to me. I value his life and existence more than you think. A rough gem only needs some polishing."
"Do you take me for a fool, Aizen Sousuke?" Isshin's jaw tightened.
"In a way, I'm the one who brought you and your wife together," Aizen said smoothly. "Is this hostility truly useful?"
"You know how many people want to kill you, right?"
"Thinking and doing are different concepts, Captain Kurosaki."
Aizen's voice lowered, quiet under the crimson light.
"Many times, I wished I could be an ordinary Shinigami. But I can't. My ability and knowledge are like a curse. They force me onto a road no one else walks. That is what powerlessness means, Captain Kurosaki."
Isshin clicked his tongue.
If he still had his Shinigami strength, he would have cut Aizen down without hesitation.
But he didn't.
So he was forced to listen.
As if he had not provoked Isshin enough, Aizen stopped in front of him, adjusted his glasses, and spoke with the calm certainty of a man stating tomorrow's sunrise.
"Then I hope to meet Ichigo Kurosaki properly."
"If you touch Ichigo or my family," Isshin growled, "I guarantee you'll die a horrible death."
"The Final Getsuga Tensho," Aizen said, unhurried, "a power that surpasses Shinigami, released by fusing one's spiritual power with one's Zanpakuto. A secret technique of the Shiba family."
His tone remained polite, almost academic.
"The Shiba family, who could master methods that reach the Royal Palace, would not have such shallow foundations. I know where your confidence comes from. You believe that without the Hogyoku, the Final Getsuga Tensho, combined with other Shiba techniques, could resist Kyoka Suigetsu's interference for a short time."
He looked at Isshin directly.
"But unfortunately, I have no intention of making enemies."
"To say nonsense even now," Isshin spat.
"This is not about being enemies, former Captain Shiba Isshin," Aizen replied. "Even Hirako Shinji, and the Hollowfication incident back then."
His eyes lowered, voice steady, magnetic.
"They simply met my criteria and entered my experimental range. I did not want to be their enemy. It just happened that they became one, and so did I. It was necessity, within an experiment."
Aizen's gaze lifted again.
"And now I've found another path. So I'm inviting you. That's all."
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