The sky gradually darkened.
Masatsuki Aozaki left the 1st Division barracks.
With Yamamoto's permission, he was no longer required to stay in the 4th Division for observation, giving him a rare moment of free time.
Still, he made a brief stop at the 4th Division to inform Retsu Unohana, Yoruichi, and the others before leaving Seireitei.
...
District 62 of Rukongai at night was a place where thieves and vagrants lurked. The streets were silent, the moonlight and starlight casting a dim glow over the darkened world.
Masatsuki Aozaki stood deep in the forest, silently surveying the small hut in front of him. The rustling of leaves in the wind stirred memories from years ago.
Four or five years prior, he had been in a similar forest—though far from here.
Beneath the same moonlit sky, a bespectacled man had stood in the shadow of a tree, looking at him with a gentle smile.
Masatsuki Aozaki extended his hand toward the ground. A faint glow of Reiatsu flickered like a firefly in the darkness.
Ripples spread across the ground, a wooden cabinet trembled slightly, and the floor shifted and rearranged itself like a puzzle coming apart. A gap opened beneath him.
Stepping forward, Masatsuki Aozaki descended a long flight of stairs, entering a dimly lit underground chamber.
The room was filled with an array of sophisticated equipment.
Originally, it had been nothing more than a crude hideout. It wasn't until he had plundered Mayuri Kurotsuchi's lab equipment that it started to resemble an actual research facility.
He pressed a hidden mechanism on the wall.
With a click, the walls split apart, wooden panels folding outward to reveal a concealed collection.
A faint blue glow illuminated the interior, revealing rows of glass jars and vials.
"The Nest of Maggots really is a goldmine."
Masatsuki Aozaki couldn't help but sigh in admiration as he took in the results of his labor.
Inside the transparent jars, black soul orbs floated, wreathed in wisps of violet smoke. Upon closer inspection, there were nearly a hundred in total.
These were his collected experimental materials.
The orbs served as containers for souls, storing those of Shinigami or individuals with Shinigami potential.
More than half had been sourced from the Nest of Maggots.
The souls from there were of particularly high quality, and the occasional disappearance of an inmate would hardly raise suspicion.
After all, in that prison, suicides due to mental breakdowns were far from uncommon.
Masatsuki Aozaki stepped toward the center of the chamber and retrieved his most valuable specimen—
The soul of Kenpachi Kiganjō.
Encased within this soul orb was the largest fragment of the Soul King among all his collected materials.
Combined with the sheer strength of Kiganjō's soul itself, its value far surpassed dozens—if not hundreds—of the other soul orbs.
Masatsuki Aozaki stood before the experiment table, adjusting the machine's controls. The platform holding the souls extended outward.
In one hand, he held Kiganjō's soul. In the other, he retrieved an ancient soul long sealed away.
He had witnessed Aizen's process for soul fusion before—using specialized filtration devices to merge completely unrelated souls into a single orb.
The soul orbs themselves had the natural ability to store and absorb spirits.
However, his attempts to forcibly merge two souls into the same orb had always ended in failure—resulting in shattered orbs and dissipated souls.
These repeated failures made it clear to him that, in the realm of scientific research, he was a complete amateur.
Rather than rushing into further experiments, he had instead sought guidance from three individuals he considered geniuses, gradually refining his understanding while analyzing his past mistakes.
To his surprise, Kirio Hikifune and the others had gladly agreed to teach him.
Given his role as an advisor to the Shinigami Research and Development Institute, it made sense that he would want to expand his scientific knowledge.
As for the Hōgyoku—since its creation was an ethical transgression, Aizen had taught himself everything, gathering, compiling, and studying research data on his own.
Strangely, Aizen had never made any real effort to hide his knowledge.
Aside from the core secrets of the Hōgyoku itself, the rest of his research materials were left open for Masatsuki Aozaki to study freely.
Perhaps it was because Aizen held absolute confidence in his own intellect...
He himself had never achieved any meaningful breakthroughs in this research, so he didn't believe that Masatsuki Aozaki could surpass him under the same conditions—let alone catch up.
In a way, Masatsuki Aozaki seemed to be retracing Aizen's old path.
However, unlike Aizen, Masatsuki Aozaki had more than just a genius friend and a genius prisoner.
He also had Kirio Hikifune, who, for now, had no equal in the field of soul research.
Masatsuki Aozaki concealed the true nature of his Hōgyoku research, but by subtly inquiring about technical details, he was still able to gain valuable insights.
His usual eccentric and unserious demeanor had already left an impression on the three of them.
Rather than suspecting his true intentions, they were simply amazed that someone as whimsical as him could occasionally come up with good ideas.
By briefly skimming through Aizen's lab notes and consulting Kirio Hikifune and the others to clear up his doubts, Masatsuki Aozaki had already gained substantial knowledge.
Before long, as his studies deepened, he finally grasped the conditions necessary for soul fusion.
While summarizing what he had learned, he began drafting the next phase of his experiment.
With his current laboratory equipment, he could now barely attempt a soul fusion experiment.
After a brief moment of contemplation, he put aside Kiganjō's soul.
To be cautious, he retrieved another soul orb containing a fragment of the Soul King.
The soul of a captain was a rare resource, so he decided to start by experimenting on less valuable souls.
In Masatsuki Aozaki's plan, the foundation of the Hōgyoku would still be Soul King fragments, as they were the key to soul fusion.
However, before the fusion, these souls needed to be purified through several specialized instruments to remove any external Reishi interference, reducing them to their purest state.
Fortunately, Mayuri Kurotsuchi had left behind plenty of such equipment.
Before his imprisonment, Mayuri's primary research subjects had been the Quincy, who were all living beings.
To study them within Soul Society, it was necessary to first turn them into the dead—especially in the absence of a Reishi conversion device.
Not only did he have soul filtration devices, but he even had equipment designed specifically to capture Quincy souls.
When a Quincy dies, their soul naturally returns to their progenitor, Yhwach—yet this madman had managed to snatch souls directly from Yhwach's grasp.
There were only two true challenges in the entire plan.
First, how to filter out the impurities within a soul and refine it into a purer state.
Second, acquiring fragments of the Soul King for the experiment.
Now, both obstacles had a solution.
...
Crushing a soul orb that did not contain a Soul King fragment, Masatsuki Aozaki watched as a wisp of purple mist rose from his palm. Stabilizing the dissipating soul, he carefully placed it into the filtration device.
Soul purification was an intricate process. Since he was still unfamiliar with the technique, it took him a full two hours to complete.
After running a final analysis on the purified souls using a high-precision viewer,
Masatsuki Aozaki observed that both souls had suffered minor damage, though the extent was negligible.
Next, he injected the two souls into a soul orb and waited silently for the result.
Before long, the orb emitted a faint sky-blue glow.
Masatsuki Aozaki remained calm, monitoring its state through the instruments.
As the glow gradually faded, the orb's smooth surface began to grow uneven, its size increasing slightly.
Simply put, it was changing from the smooth texture of jade to the rough appearance of a lump of coal.
(40 Chapters Ahead)
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