Most of this vitality is tied to one's own abilities.
For example, in the original story's four Schutzstaffel: one has piercing attacks and constant regenerative evolution; one grows bigger and stronger when injured; one gradually becomes immune to spiritual pressure; and one evolves resistance to attacks and keeps splitting and regenerating.
After Yoshio completed his evolution, he also gained powerful immortality. Even if he's killed, he can regenerate in the Hell of Solitude.
It's a bit like the beings in Hell.
People in Hell don't die—because that's their punishment: eternal life in that infernal place, which means eternal torment.
And Yoshio gained that trait through the Hell of Solitude.
"Not bad…"
Yoshio was in a pretty good mood.
After all, he'd just pushed his soul strength past the Shinigami limit in one go. In the Three Worlds, there probably aren't many who can match him now, right?
With that thought, Yoshio began suppressing his aura again.
Then he took a close look in the mirror. The Hollow mask on his face was gone, and the Hollow hole had vanished. He looked like his old self again, but there was an intangible pressure about him.
If he wished, the spiritual pressure in his body could form a super reiatsu wall around him.
This super reiatsu wall lets him ignore a portion of damage caused by reiatsu. As he grows stronger, the wall will only get stronger, and one day it will completely nullify all damage from anything below his tier.
That means he basically doesn't have to worry about getting overturned when strong bullying weak.
In the original, with the super-level reiatsu wall of the Hogyoku's third phase, Aizen made the kototsu that rammed into him backfire and explode outright!
The kototsu isn't some simple thing—it's the condensation of time and space in the Three Worlds, representing spacetime, essentially a construct at the level of rules.
It should be one of the Three Worlds rules set by the Five Great Noble Houses when they used the Soul King's power to create the world.
Many captain-class Shinigami certified that the kototsu isn't something Shinigami can handle—yet Aizen easily destroyed it.
Of course, that destruction isn't permanent.
Theoretically, the kototsu is also a Transcendent. Since it's a Transcendent, naturally it has immortality.
So it revives seven days after being destroyed by Aizen.
Yoshio's current super reiatsu wall hasn't reached that level yet—unless he uses the power of the Left Arm of the Hollow King.
Having clarified his current state, he relaxed.
He'd been taut for so long—now he could finally unwind.
Yoshio lay down for a bit, then looked at Masaki Kurosaki sealed inside the experimental device.
Her soul attributes had been fully analyzed, and all the prep work was done. It was time to let her out.
Yoshio walked up to the device, operated it for a while, then took out the Hogyoku.
As the Hogyoku gleamed, Masaki Kurosaki inside the sealed instrument reacted at once.
A large amount of nutrient solution flowed in, soaking her. Her body began to tremble unconsciously.
A surge of spiritual power welled out from her soul core. Her everyday clothes turned black and finally became a shihakushō.
Although the data had been set up, it was still uncertain whether Death apotheosis could suppress the influence of that Auswählen. Her soul had been permanently damaged when Yhwach unleashed Auswählen, and was almost constantly pulled toward the main body of the Auswählen.
At this moment, Yoshio had used the Hogyoku and some other gadgets to convert Masaki Kurosaki into a Shinigami, but he still hadn't awakened her—further testing was needed.
Yoshio took a bottle of cola from the fridge, gulped a mouthful, then sat back at the computer. After checking the data, he frowned.
After Death apotheosis, Masaki Kurosaki's soul wounds seemed somewhat repaired, but some Auswählen seeds remained.
Although Shinigami and Quincy are opposites, Hollows are the Quincy's true nemesis.
Yhwach is more than happy to absorb Shinigami power.
Looks like he can only convert Masaki Kurosaki into a Hollow.
He just didn't know if Masaki would lose her sanity after becoming a Hollow…
If she really turned into another White-like case, this move would be pointless.
But…
He was a Hollow King now!
A Hollow King has an innate dominion over Hollows; he can control all Hollows below Vasto Lorde.
Even over Vasto Lordes, he exerts some influence.
Of course, if they're Arrancar, the control drops a tier.
But in Masaki Kurosaki's current state, she clearly doesn't have Vasto Lorde-level power.
After being Ausgewählt, her strength had fallen below even a Menos Grande.
So Yoshio was confident he could influence Masaki Kurosaki.
He took a deep breath, finished the cola in one go, and proceeded with the conversion.
The technology to convert a Shinigami into a Hollow was already mature; he didn't need Hogyoku assistance.
And converting Shinigami toward Hollow involves much bigger changes than converting Quincy toward Shinigami.
Not long after the experiment began, Masaki's expression contorted. Her soul, which had been sleeping, awakened in an instant. She opened her eyes wide, mouth agape, and let out a sharp, painful screech!
Roar!!
Violence was contained in that sound. Masaki's body thrashed wildly. Fortunately her hands and feet had been chained; even so, the device looked about to break.
"Calm down. My equipment is expensive," Yoshio said coolly.
With just that one line, the roaring Masaki froze in place, as if suppressed by instinct.
She looked in great pain—torn between the Hollowing instinct to vent and destroy, and the king's command not to move.
Caught in this contradiction, her features twisted; she could only roar to vent.
At that moment, the second phase arrived.
Just like Yoshio's own Hollowfication before, a white substance secreted onto Masaki's face to form a mask, and a black hole slowly opened in her chest.
Only, her Hollowfication was even more thorough than Yoshio's had been: after those two changes completed, a black substance started to proliferate across her skin.
As if her shihakushō had melted, the proliferating black substance combined with the shihakushō to form a shell like mechanical armor.
Masaki's physique didn't change, but a crescent appeared on her right hand—like a bow.
This bow was integrated with her right hand and was white, as if her bones extended outward.
"…Looks like it worked."
Yoshio looked at Masaki's current state. From the exterior, there was no trace of the former Masaki Kurosaki.
And she had no reason left. She looked no different from a soul fallen into Hollow—er, not quite. More like White.
Most Hollows have white outer shells; only she and White—Hollows formed from Shinigami souls—are black.
Masaki's case is even more complex: Quincy restructured into Shinigami, then Shinigami transformed into Hollow.
Although she seemed utterly mindless now, Yoshio figured he could wait.
Masaki's will was fairly firm—she might force her consciousness awake.
If Sora Inoue could do it, Yoshio believed Masaki could do even better.
First, let her regain self-awareness.
"You stay here. Don't break anything."
Once the transformation was done, Yoshio released Masaki from the device.
She seemed dazed. With her destructiveness suppressed by Yoshio the Hollow King, this newborn Hollow was like an infant.
With Masaki's matter settled, Yoshio stretched.
Time to make his move.
The first thing he did was go check the world outside.
…
Three years had passed; Karakura Town had developed further.
Although the Brainleaf Co. headquarters had moved, even a branch kept boosting surrounding industries. Karakura Town's GDP surged; the once ordinary town was no longer ordinary.
Karakura Town officially connected with Tokyo and became the most important ward; now it could be called Karakura Ward.
But one thing surprised Yoshio.
He'd thought the Shinigami were just performing for the bureaucracy, faking an investigation in the living world and pulling out soon.
But three years later, the Seireitei had not given up.
On the contrary, their presence intensified.
There were more and more Shinigami in Karakura Town now.
He sensed it: the reishi density in Karakura hadn't grown much more. First, after Brainleaf Co. moved, the place didn't attract Menos as much.
Second, many Shinigami had come. With Shinigami guiding, they would even choose to disperse Hollows instead of kill, unless necessary—so the reishi density remained at about one-fifth of Soul Society's.
For the living world, that's high, but it hadn't caused huge changes.
It did mean more Hollows came to Karakura Ward.
Previously, the 13 Court Guard Squads only needed one Shinigami stationed there. Now there were upper seats from the 10th, 11th, and 13th Divisions, plus many regular Shinigami.
With that many, they could maintain order in Karakura Ward.
And…
There was another interesting matter.
Originally, Mayuri had been eager to move against Sōken Ishida and Gabriel, but after being seriously injured by Gabriel and recuperating, he had no chance to target Sōken.
With so many Shinigami in Karakura now, he couldn't even lure Hollows to attack Sōken.
And they were from other Divisions—Mayuri couldn't command them.
Plus the one he hated most was Gabriel; over the past few years, he was distracted by their cat-and-mouse.
Everyone else remained in hiding.
Hela had recently returned to Karakura and gone back to her old trade—teaching English at Karakura First High School.
Nezuko had been living as an ordinary grade-schooler; now she was in middle school.
Brainleaf Co.'s workload wasn't as heavy as at the beginning.
Seeing the living world thriving, Yoshio returned to Soul Society.
He first went home. At night, the second Yoshio came back; Yoshio reached out, and a spatial gate opened.
That Yoshio returned to his original world.
That guy's mission was complete. In exchange for vanishing three years, he'd gained captain-class strength.
After Yoshio returned, he went straight to Aizen.
"Got it handled?"
Aizen wasn't surprised to see Yoshio. "The Three Worlds haven't been very peaceful lately."
"It's fine. They didn't find me, did they?" Yoshio smiled. "Captain Aizen, are you interested in using the Mind-Rending Blade?"
"Looks like you're a bit impatient too." Aizen chuckled. "You've been waiting for this moment from the start, haven't you?"
Yoshio gave an awkward yet polite smile. "Come on, I just want to see what someone completely opposite to Captain Aizen is like."
"You can try."
Aizen looked at Yoshio.
By now, their relationship had become what it was at the start.
When they first met, Yoshio said he just wanted to observe, and stayed by Aizen to observe.
But back then Yoshio wasn't strong enough, so he seemed like Aizen's subordinate.
Until now—Yoshio had surpassed Aizen, and their relationship finally became what they'd originally set.
Yoshio had surpassed Aizen but hadn't struck out alone or betrayed him; he appeared by Aizen's side like an observer.
Only when they truly stood as equals—indeed, with Aizen weaker and Yoshio stronger—did Aizen's favorability toward Yoshio improve.
Aizen probably viewed Yoshio as a Kisuke Urahara PLUS.
Intelligence aside, he was stronger, higher in essence, and unlike Urahara, not a slacker.
Knowing that, Yoshio was relaxed with Aizen.
He took out the Mind-Rending Blade. "Captain Aizen, why don't you do it yourself?"
Aizen chuckled. "Can't bear to lay hands on the old Captain?"
"You put it that way, I'll do the cutting."
Yoshio gripped the Mind-Rending Blade and slashed at Aizen in an instant!