Upon hearing Gosuke Shigure's explanation, Urahara Kisuke's interest was immediately piqued.
Several years earlier, during a Konsō (Soul Burial) field exercise in the Human World, students from the Shin'ō Academy had encountered a Hollow that was later confirmed to be one of Aizen's experimental creations. At the time, Hisagi Shūhei, who was then serving as a seated officer of the Ninth Division, had attempted to fight the creature.
Despite his efforts, he was completely outmatched.
The Hollow's strength had been overwhelming for someone of his level.
In the end, in order to prevent the situation from escalating and drawing unnecessary attention, Aizen Sōsuke himself had intervened and personally destroyed the Hollow.
Urahara had never expected that several years later, Gosuke Shigure would appear with the corpse of another one of Aizen's experimental subjects.
The fact that Shigure had brought it here meant only one thing
This Hollow was far from ordinary.
Especially considering what Shigure had just said.
It had nearly killed Shiba Kaien, Vice-Captain of the Thirteenth Division.
Urahara Kisuke had certainly heard of Kaien.
Although he had been exiled from Soul Society for many years, Shigure occasionally shared information with him, allowing him to remain aware of important developments within the Gotei 13.
Kaien's name was among those.
The current head of the Shiba family, Kaien was widely regarded as a prodigy. When he first entered the Shin'ō Academy, his spiritual power had already reached sixth-class Reiryoku, far beyond that of typical students.
After ten years of training, he graduated.
Five years later, he had already risen to the position of Vice-Captain.
Such a figure being pushed to the brink of defeat…
Naturally sparked Urahara's curiosity.
"What exactly can this Hollow do?" he asked.
Shigure answered calmly.
"In addition to possessing the High-Speed Regeneration typical of Menos-class Hollows, it also has an ability to devour spiritual attacks. Any technique composed of condensed Reishi such as Kidō or Zanpakutō techniques infused with Reiatsu can be absorbed upon contact."
He paused briefly before continuing.
"Furthermore, it can interfere with a Shinigami's Zanpakutō, effectively rendering it unusable."
"Oh?"
Urahara's eyes lit up behind the brim of his hat.
"In that case… this is indeed a very valuable specimen."
Although Shinigami possessed many techniques, their combat methods were traditionally categorized into four primary disciplines:
Zanjutsu, Hakuda, Hohō, and Kidō.
Zanjutsu referred to combat using the Zanpakutō.
Hakuda covered hand-to-hand combat.
Hohō included movement techniques such as Shunpo.
And Kidō encompassed spiritual spells used for offense, defense, and binding.
If this Hollow truly possessed the abilities Shigure described, then most conventional Shinigami techniques would be rendered ineffective.
Kidō relied entirely on condensed Reishi making it vulnerable to the Hollow's devouring ability.
Its interference with Zanpakutō would effectively cripple Zanjutsu.
That left only two viable options in combat:
Hakuda and Hohō.
No wonder Shiba Kaien had nearly been killed.
Facing such a creature without prior knowledge of its abilities would have been extremely dangerous even for a Vice-Captain.
Realizing this, Urahara's interest deepened further.
Even though what lay before him was only a corpse, it still possessed tremendous research value.
If he could analyze the mechanism behind these abilities, he might be able to develop entirely new technologies.
For example
If the Hollow's devouring ability could be replicated or adapted, it might lead to the creation of devices capable of absorbing Reishi-based attacks.
Such technology would not only be effective against Kidō, but also against another type of enemy who relied heavily on manipulating Reishi
The Quincy.
As for the ability that interfered with Zanpakutō…
Even if it primarily targeted Shinigami, understanding its mechanism could still yield useful applications.
After all, knowledge itself was never useless.
"This is excellent experimental material," Urahara said sincerely. "Thank you, Sensei."
Shigure simply smiled and said nothing more.
Since delivering the specimen had been his primary purpose in coming to the Human World, he did not remain long. After handing the Hollow corpse to Urahara, he soon returned to Soul Society.
Meanwhile, somewhere within Seireitei
Aizen Sōsuke had already noticed that one of his experimental subjects had disappeared.
Ever since he had shifted his focus away from experimenting on Shinigami, most of his research had been conducted in Hueco Mundo.
Compared to Soul Society, Hueco Mundo was far more convenient.
In Soul Society, the disappearance of even a single Shinigami would inevitably attract attention from the Gotei 13.
But in Hueco Mundo?
Hollows devoured one another constantly.
Countless Hollows were born every day, and countless others vanished just as quickly.
It was a world governed entirely by the law of the jungle.
Even with a high failure rate in his experiments, the sheer number of Hollows ensured that successful results would eventually appear.
By studying Hollowfication in reverse transforming Hollows toward a more Shinigami-like state—Aizen had succeeded in creating a new class of beings.
Arrancar.
Before that, the evolution of Menos had been divided into three well-known stages:
Gillian, Adjuchas, and Vasto Lorde.
Among them, Vasto Lorde stood at the apex.
Yet after undergoing Arrancarization, even an Adjuchas-class Hollow could surpass the power of a traditional Vasto Lorde.
The key lay in their ability known as Resurrección the release of an Arrancar's sealed power.
Each Resurrección manifested unique abilities based on the Hollow's original nature.
In terms of versatility, many Arrancar possessed powers far more varied than those of ordinary Menos.
As for a Vasto Lorde that had become an Arrancar
Its strength was on an entirely different level.
The success of the Arrancar project had filled Aizen with confidence.
But he was not satisfied.
A new idea had already begun forming in his mind.
If a naturally evolved Hollow could become so powerful after Arrancarization…
Then what would happen if he artificially created a special Hollow with unique abilities, and then forced it to undergo Arrancarization afterward?
Would those abilities evolve even further?
Over the years, Aizen had created numerous experimental Hollows.
Metastacia was one of them.
Its defining ability was adaptive devouring, allowing it to evolve through consumption. Additionally, it possessed the unique trait of interfering with Zanpakutō, making a Shinigami's blade useless.
Aizen had deliberately allowed it to appear within Soul Society.
His expectation was simple.
Once confronted by Shinigami, the creature would devour them and in doing so, he might observe whether it could acquire their abilities.
Unfortunately
The experiment had ended sooner than expected.
Metastacia had been destroyed before fulfilling its intended role.
Although Aizen had not personally witnessed the battle, the residual Reiatsu left at the scene told him everything he needed to know.
"Gosuke Shigure…"
Aizen murmured quietly inside the Fifth Division barracks.
Behind the lenses of his glasses, his eyes narrowed slightly.
"The retired Kenpachi."
"It seems even someone who left the battlefield… can't completely resist interfering."
His tone remained calm.
But beneath that calmness
A subtle curiosity had already begun to form.
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