Joint Investigation  

"Troubled times indeed..." Shunsui Kyōraku sighed, rubbing his temples. Why was it always him who ended up dealing with these situations?

The truth was, both Ailin and his clone, upon hearing Mayuri Kurotsuchi's findings, had instantly understood the implications. Naturally, their expressions shifted, revealing a flicker of recognition.

However, Ailin's clone, masquerading as Sōsuke Aizen, had subtly manipulated Shunsui's perception using Kyōka Suigetsu, allowing him to see only what Ailin desired. Ailin's main body, on the other hand, hadn't bothered with such deception. His reaction was genuine, easily observed by Shunsui.

Perhaps Ailin would never have imagined that his honesty, his willingness to share information about Aizen with Shunsui, would backfire, sowing seeds of doubt in the captain of the 8th Division's mind.

Head-Captain Yamamoto surveyed the assembled captains, his gaze sharp and unwavering. Hollowfication experiments were no trivial matter. To conduct such research, one required two essential elements.

First, strength. Without sufficient power, if the subject lost control and went on a rampage, who could possibly stop them?

Second, scientific aptitude. Without a keen understanding of science and practical experience, even with access to Hollow reishi, one wouldn't know how to initiate a reaction between it and a Shinigami's soul, achieving Hollowfication.

The pursuit of strength was an innate human desire, amplified within the hearts of Shinigami. However, increasing one's power wasn't a simple task. Every Shinigami had their limits.

Some were born at the pinnacle.

Zaraki, for instance, possessed monstrous spiritual pressure from birth. As a child, without any formal training in swordsmanship, relying solely on instinct, he had defeated Yachiru Unohana, the first Kenpachi. He was a natural prodigy, destined for greatness.

Others were destined for greatness from the moment they were chosen.

Toshiro Hitsugaya, wielding Hyōrinmaru, the strongest ice-type Zanpakutō, was an example. His potential was tied to the limits of his Zanpakutō.

Then, there were those whose exceptional talent and dedication allowed them to ascend to the peak through sheer effort.

Yoruichi Shihōin was one such individual. She lacked Zaraki's innate power and hadn't been chosen by a "strongest" Zanpakutō. However, her training aptitude was unmatched, her progress in decades surpassing that of others in centuries.

Moreover, she had even developed a technique rivaling the power of a Zanpakutō release, "Shunkō," a fusion of Hakuda and Kidō. Her talent and ingenuity were undeniable.

These individuals had no need to worry about their strength. Given enough time, they would naturally surpass their peers.

However, not everyone was content with their limits.

When a Shinigami felt they had reached their peak, with no further room for growth, they sought alternative methods to break through.

Scientific research became their only hope.

The former captain of the 12th Division, Kirio Hikifune, was a prime example of this path's success. Through her research, she had developed "Artificial Souls," consumable souls that could be implanted within a Shinigami, boosting their spiritual pressure. She had successfully used this technique to surpass the limits of a Shinigami.

However, experiments were inherently risky.

Over a thousand years ago, the precursor to the Shinigami Research and Development Institute had initiated the "Soul Reaper Project," an attempt to create artificial souls, a predecessor to Hikifune's work. Sadly, the experiment had gone awry, resulting in a massive explosion that had devastated a tenth of the Seireitei, breached the barrier between the Soul Society and the World of the Living, and unleashed modified souls into the human world, giving rise to the immortal Bounts.

It was no secret that some Shinigami, frustrated by their stagnant growth or seeking further power, turned to research to achieve their goals.

In its million-year history, the Soul Society had witnessed countless experiments, many of which had resulted in devastation and unforeseen consequences.

Hollowfication experiments were among the most dangerous.

While the data from many of these experiments had been sealed away by the nobles, inevitably, over the centuries, others would retrace the steps of their predecessors, driven by the same thirst for power.

To prevent further disasters, the nobles had authorized the creation of an organization that would eventually become the Shinigami Research and Development Institute. This organization, along with the 12th Division, provided a controlled environment for Shinigami to pursue their research.

Of course, this "controlled environment" meant constant monitoring by the nobles.

Any research deemed too dangerous or resembling forbidden experiments would be met with swift punishment from the Central 46, the research data confiscated, and the researchers imprisoned.

Through this system, the nobles had effectively curtailed many potentially catastrophic experiments.

However, some individuals still managed to operate beyond their control, conducting their research in secret.

Kisuke Urahara was one such individual. His Zanpakutō, Benihime, possessed the power to restructure matter, transforming any location into his personal laboratory.

And then there was Sōsuke Aizen… He could probably infiltrate the 12th Division's laboratory, utilize its equipment, and complete his experiments without anyone even noticing.

The captains, listening to Kurotsuchi's findings, remained silent. Decades ago, Urahara had been exiled from the Soul Society for his Hollowfication experiments. His laboratory had been sealed by the Central 46. The Hollow Kurotsuchi had encountered couldn't possibly be a remnant of Urahara's work.

It meant that someone else, within the Seireitei, was conducting Hollowfication experiments.

Bang!

Yamamoto slammed his staff against the floor, his eyes snapping open, unleashing a wave of spiritual pressure that washed over the room. His fury was palpable.

"Captain Soi Fon of the 2nd Division, Captain Shunsui Kyōraku of the 8th Division."

"Head-Captain," Soi Fon and Kyōraku stepped forward.

"I expect you to uncover the origins of this Hollow with all due haste. Should you find anything…" Yamamoto's gaze shifted to Ailin. "Captain Ailin of the 11th Division."

"Present, Head-Captain," Ailin responded.

"I want you to accompany Captains Soi Fon and Kyōraku throughout this investigation. Should they uncover anything, you are to apprehend all those involved."

"Understood!"

The other captains, observing the situation, recognized the Head-Captain's determination. Ailin rarely involved himself in division affairs, preferring to spend his days within the Kuchiki estate. The 11th Division was practically run by its vice-captain, Zaraki.

The fact that Yamamoto had specifically chosen Ailin to oversee this investigation, demanding his direct involvement, spoke volumes about the severity of the situation.

"The rest of you, be vigilant. Ensure that no other Hollowfied Shinigami appear within the Seireitei."

"Understood!"

…

After leaving the meeting chamber, Ailin walked alongside Soi Fon and Kyōraku.

"Soi Fon, Kyōraku, what are your thoughts on this situation?"

"Anyone involved in Hollowfication experiments deserves to die!" Soi Fon growled, her face contorted in a mask of rage, as if those conducting the experiments had committed some personal offense against her.

Ailin chuckled awkwardly, understanding that Soi Fon was projecting her hatred for Urahara onto anyone involved in Hollowfication research.

He couldn't fault her for her feelings. After all, it was Urahara's actions that had led to Yoruichi abandoning her, fleeing to the World of the Living with Urahara and the Hollowfied captains and lieutenants.

"And you, Captain Kyōraku?"

"Sigh… There isn't much to go on. We can only investigate further, see if we can uncover any leads."

Kyōraku wasn't optimistic about their chances. Over the years, he hadn't found a single shred of evidence to incriminate either Ailin or Aizen.

Actually, Aizen had left a trail of clues.

However, those clues felt more like deliberate taunts, mocking those attempting to expose him. It was as if he was saying, "I've given you every opportunity, but you're still incompetent."

This Hollow, the one with Shinigami reiatsu… Perhaps it had been released by one of their subordinates. But after so much time, the evidence would have been meticulously erased.

"Captain Soi Fon, while both the 2nd and 8th Divisions have intelligence units, the 8th focuses primarily on matters outside the Seireitei. For internal investigations, the 2nd Division is more adept. I believe it would be more efficient if we split the investigation. You handle matters within the Seireitei, while my division investigates Rukongai."

For Kyōraku, regardless of whether Ailin or Aizen was the mastermind, neither was an opponent he could handle. It was better to focus on increasing his own strength while they were still in their "incubation phase."

With the power of his Zanpakutō, once his spiritual pressure reached a certain level, he would be able to challenge either Ailin or Aizen.

Since this Hollow had been discovered within the Seireitei, Kyōraku wanted nothing to do with it. If they uncovered something substantial, it might provoke one of them, leading to an unwanted confrontation. It was better to let Soi Fon handle this mess.

"Indeed. That would be the most efficient way to proceed," Soi Fon agreed, nodding.