Urahara Kisuke took the Soul King Fragment he had obtained from Kuchiki Aoba and processed it before embedding it into the prototype Hōgyoku.
Though his research on the Hōgyoku had begun later than Aizen Sōsuke's, their methodologies differed greatly—making Aizen all the more fascinated. Standing silently nearby, he watched every step of Urahara's process, trying to reverse-engineer his thinking.
"The approach is different from mine... but the principles resonate," Aizen murmured, stroking his chin as he observed intently, unwilling to miss a single detail.
Under Urahara's careful manipulation, the once-incomplete Hōgyoku began to grow.
By the time it had fully absorbed the fragment from the Kuchiki Clan, it had swelled to many times its original size.
"This one might actually be stronger than the one I made," Aizen thought, unable to suppress his admiration. "As expected of one of the oldest clans… the Kuchiki family had quite a stash of Soul King Fragments."
Soul King Fragments were exceedingly rare—even most minor nobles had never heard of them.
But the true aristocratic clans… they possessed legacies unimaginable to outsiders. With the materials he'd obtained, Urahara's progress had taken a massive leap forward.
"Based on what I've seen in old records... aside from the Shiba Clan, the other four Great Noble Houses should all possess Soul King Fragments," Aizen mused.
He was certain the Shiba had none—he'd searched their sealed vault himself years ago.
He used to "visit" the Shiba quite frequently in his youth. There was nothing in their treasury he hadn't already examined.
"The Tsunayashiro clan's fragments are all in Sensei's lab. As for the Shihōin… I'm sure he took theirs too."
Aizen doubted his teacher would've overlooked the Shihōin's collection, and mentally crossed them off his list.
"That just leaves one Great Noble House…"
Aizen made a note to pay them a visit when the time was right.
Meanwhile, Urahara had finished merging the fragment and began testing the Hōgyoku's properties.
Unlike Nanatsuki or Aizen, however, he wasn't interested in using the Hōgyoku to evolve Hollows.
He lifted the orb and approached two nearby incubation tanks.
"Oh...?" A playful smile spread across his face. "With this, maybe I'll catch up faster than I expected."
If Mayuri Kurotsuchi saw what floated inside those tanks, he would likely smash them on the spot.
Floating inside were artificial soul embryos.
Mayuri had always believed himself more talented than Urahara, sparking an ongoing rivalry between them.
But that only made Urahara more competitive.
Creating independently growing artificial souls was Mayuri's dream.
So Urahara intended to beat him to it—and by helping fulfill that dream first, he could drive Mayuri up the wall.
He felt completely confident now. With the improved Hōgyoku, he could directly repair the flaws in artificial soul development.
The previous version, which had only absorbed a small amount of Soul King Fragment, hadn't been powerful enough to perfect the embryos. Still, it had brought him only a few years behind Mayuri's progress.
He hadn't paid much attention to artificial souls before. Only after sensing Mayuri's imminent success had he jumped in.
That gap had been over a decade.
But with this newly empowered Hōgyoku, he could leapfrog the competition in one bound.
He activated it with a thought. The Hōgyoku darkened and extended black tendrils that pierced into his fingertip.
The orb blazed with radiant light, enveloping both embryos in the incubation tanks.
Moments passed. Then the light dimmed.
"Did it… work?"
Urahara hesitated. The embryos didn't look any different.
He adjusted the settings and drew out some cells to examine under the microscope.
After a while, he scratched his head, no closer to an answer.
"Doesn't look like there's a problem… guess I'll proceed with cultivation and monitor results."
He recorded the data meticulously.
If successful, this would confirm the Hōgyoku's power to correct the core deficiencies of artificial souls. He adjusted the nutrients in the tank, removing the previous growth inhibitors.
"If this works..." Urahara gazed at the orb in his hand, "...then it's nothing short of rewriting the Creator's will."
Artificial souls were fundamentally different from Reishi Shells. They weren't transplanted into host bodies—they were born from nothing, crafted from ordinary Reishi into true soul entities.
Their very existence challenged the fundamental logic of soulbirth, once limited to natural human reproduction or soul division.
"So… he's using the Hōgyoku to correct flaws in artificial souls…" Aizen flipped through the data Urahara had just filed away.
"A technique that can't be widely distributed. Producing too many would disrupt the balance of souls between the three realms..." Aizen tapped his temple. "But if used the right way… it could preserve the balance instead."
After completing his experiment, Urahara felt fatigue wash over him. The date with Aoba had drained more energy than he expected.
He placed the Hōgyoku in a glass containment case inside a reinforced cabinet. The case was covered in multiple layered seal formulas.
If anyone touched the orb, the lab's self-destruct system would trigger instantly—and he'd be alerted as well.
What Urahara didn't realize… was that under the influence of Kyōka Suigetsu, he had never actually placed it inside.
He merely thought he had.
The Hōgyoku was still sitting on the table, unguarded.
Aizen had subtly warped Urahara's senses—making him believe the orb was safely locked away, when in reality it lay completely exposed.
The moment Urahara left the lab, Aizen stepped forward.
"I'll accept this generous gift, Urahara Kisuke."
He picked up the Hōgyoku, a satisfied smile playing at his lips.
Kuchiki Estate.
After parting ways with Urahara, Aoba returned home.
Lifting the hem of her skirt and tiptoeing across the covered walkway of the rear courtyard, she moved cautiously.
She had gone to meet Urahara in secret—being caught would be disastrous.
"Aoba."
The voice behind her was calm and familiar.
It froze her in place.