(T/N: Hello Everyone!! This is chapter 1 out of 6!
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"Sensei, I've been hiding my Zanpakutō's true ability," Aizen Sōsuke admitted after some thought.
Since Nanatsuki had already noticed his sneaky excursions into Seireitei and the noble districts—where guards strangely ignored him—he likely knew more than he let on.
This kind of ability clearly wasn't just about mist or reflections. Aizen had no choice but to be honest.
"I know," Nanatsuki replied with a soft chuckle. "Your Zanpakutō, Kyōka Suigetsu, doesn't simply control fog and water."
Aizen inwardly sighed in relief. He had made the right call.
"Yes. Its true power is sensory manipulation—controlling the five senses completely," he confessed.
"Exactly what I suspected," Nanatsuki nodded. "An excellent ability. Useful both in battle and everyday affairs."
"As expected from Sensei. Not even Kyōka Suigetsu could fool your eyes," Aizen said in awe.
"The information you found about the Soul King likely came from noble archives," Nanatsuki continued. "But even their records aren't the full truth."
"If you want deeper knowledge, consider visiting the Shiba Clan. As one of the Five Noble Houses, they may hold older records."
Nanatsuki planned to begin researching the Hollow hybrid and the Soul King's fragments. It was inevitable that Aizen would uncover the truth, so he nudged him in that direction.
"The Shiba Clan, huh... I've heard they're among the Five Great Noble Families," Aizen mused. "Understood. I'll find time to investigate."
Meanwhile, Aizen finished grinding the reagents. Following Miyamoto Tetsuya's formula, Nanatsuki began preparing a Reishi Growth Serum.
The process wasn't complex. The hybrid Hollow's blood was the core ingredient; the rest were boosters and stabilizers.
Soon, a single vial of serum was ready.
"This is what Miyamoto used to accelerate embryonic Reishi Shells. Take one of our developing Hollow Shells and inject it."
Nanatsuki selected a specimen that had matured to a basic Hollow level.
Aizen retrieved the shell and administered the serum.
There was no dramatic reaction.
Nanatsuki picked up a scalpel and gently sliced the Hollow Shell's arm. The wound closed rapidly.
This Hollow Shell lacked innate regeneration. Clearly, the rapid healing came from the injected serum.
"Its Reiryoku remains stable," Aizen noted while taking logs. "But regeneration has clearly increased."
They repeated the test several times. After thirty minutes, the regenerative effect wore off.
"It doesn't seem to boost growth much," Aizen summarized.
Compared to the fungal Hollow growth stimulant he developed, this had less impact on Hollow growth.
"That's expected," Nanatsuki said. "It seems to affect Shinigami-type Reishi more. The Hollow-based serum amplifies Hollow growth, but this one may stimulate Shinigami Reishi better."
According to Miyamoto's records, the growth catalyst worked far better on Shinigami Shells—even comparable to how the fungal stimulant boosted Hollow Shells.
The fungal stimulant worked by leveraging Hollow predation instincts. Distilled into a serum, it could outperform even the act of devouring another Hollow.
"So Hollow and Shinigami energies really do influence each other," Aizen muttered. "It's... fascinating. Sensei, do you think this serum could affect normal Shinigami too?"
He couldn't help but wonder—if it worked on Reishi Shells, maybe it would affect full-fledged Shinigami.
"Miyamoto already tested that on himself," Nanatsuki replied, pulling documents from his Reishi Pocket. "Back when he was just a Vice-Captain, he had hit a bottleneck. I found records in his lab confirming that he used the serum to reach Captain level."
"We have a mountain of data. Yoruichi will bring more backup files from the Detention Corps later. For now, let's start combing through what we have."
Eventually, Nanatsuki pulled out the relevant file.
"He really reached Captain-class through the serum?" Aizen was stunned. It worked even better than expected.
"Yes. He was stuck at a plateau and took the risk."
It was a bold move. Combining Hollow and Shinigami traits was dangerously unstable.
"But it came with a price. His body accumulated Hollow Reishi. Though the hybrid's blood appears mild, it still poses latent risks."
Nanatsuki frowned.
"His notes also mentioned hearing voices... a kind of inner madness. He had to rely on drugs to maintain clarity."
Nanatsuki concluded: "Miyamoto was likely on the verge of Hollowification."