After Grimmjow and Ulquiorra's training began to show results, Nanatsuki left Hueco Mundo.
He returned briefly to the Department of Technological Development.
Now that he had taken in Grimmjow and Ulquiorra, another member of the Espada came to mind—someone who might be relatively easy to persuade into becoming a disciple.
Coyote Starrk, the Primera Espada, was a lone wolf wandering Hueco Mundo.
He despised solitude and longed for companionship, but his Reiatsu was so overwhelming that ordinary Hollows were crushed into Reishi the moment they approached.
Nanatsuki wanted to find Starrk and make him his disciple.
Hueco Mundo, however, was vast—finding him wouldn't be easy.
Fortunately, the Department of Technological Development had various tools for amplifying spiritual detection.
"Off work already, Kisuke?" Nanatsuki appeared beside Urahara Kisuke in a flash of Shunpo as the latter stepped out of the department building.
"Ah... Captain!" Urahara flinched, startled as if caught doing something sneaky.
"Perfect timing—I've got a question for you," Nanatsuki smiled. "Is there any method to vastly amplify spiritual perception? Accuracy doesn't matter, only the range."
"Amplify spiritual perception, huh?" Urahara let out a subtle breath of relief, then said after a moment's thought, "I think Akon made a toy like that. Not sure if it fits your needs, but it can expand the range by several thousand times. The precision's terrible, though—you won't sense anything below Lieutenant-level Reiatsu from far away."
"Several thousand times is good enough," Nanatsuki nodded and bid Urahara farewell.
It was after hours—he wouldn't interfere with his subordinates' private lives.
Once Nanatsuki was out of sight, Urahara finally relaxed.
"Seriously, popping up behind me like that… thought I'd been caught..." He adjusted his hair and slipped on his hat, then left the building.
But instead of heading toward Rukongai, he walked in the direction of the aristocratic district.
Recently, Urahara had been reading through ancient texts and had come across some secrets. He suspected that the Four Great Noble Clans might be in possession of Soul King Fragments¹.
Ever since coming into contact with one such fragment, Urahara had been obsessed—desperate to uncover its mysteries.
But he didn't have nearly enough fragments.
To obtain more, he could either scavenge in Rukongai or target the noble families directly.
Soon, he arrived in a street lined with blooming cherry blossoms.
This area, filled with rows of refined residences, belonged to the Kuchiki Clan.
Urahara turned into a large estate's rear courtyard, where a black-haired girl in casual clothes stood waiting by the garden gate, glancing around.
"Sorry to keep you waiting, Miss Aoba," Urahara scratched his head sheepishly.
"Kisuke! Are you off work?" Kuchiki Aoba's face lit up with a smile as she ran up and hugged him.
"Keep your voice down..." Urahara ducked his head nervously. "If Captain Kuchiki finds out, we're both finished!"
"It's just some bones... what's there to worry about?" Aoba looked puzzled.
The purity in her eyes stung a little, but when Urahara caught sight of the jar in her hands, all his reason was swept away by sheer curiosity.
To unravel the truth of this world, he was willing to offer up his charm as a sacrifice.
Even if the girl before him was the younger sister of Captain Kuchiki Sōjun, discovery meant absolute ruin.
But Urahara believed the risk was worth it.
"You know our relationship can't be made public yet," he said, taking Aoba's hand in his. "But once I achieve something great, I'll come marry you."
Over time, he and Aoba had gotten along quite well.
If she managed to smuggle out the Soul King Fragment undetected, Urahara had no objections to making her his wife.
What neither of them realized, however...
At that very moment, Aizen Sōsuke stood at the opposite end of the street, watching their tender moment with interest.
"Fascinating..." Aizen stroked his chin, a sly smile creeping across his face. "So someone else in Seireitei is studying the Soul King Fragments."
The entire Court of Pure Souls was blanketed in his surveillance bacteria. Urahara knew this—and had already given Aoba a device that could mask them.
This specific street was one such blind spot.
Aizen had noticed the disruption in surveillance and came to investigate.
Urahara never suspected that he and Aoba had already fallen under Kyōka Suigetsu's Complete Hypnosis back during the Spiritual Arts Academy's Live Blade Trial² over twenty years ago.
Even now, Aizen stood quietly at the corner, completely unnoticed.
"To think I'd stumble upon something so valuable... and it's the Vice-Captain of Squad Twelve, no less..."
Aizen had just gotten off duty himself. With nothing better to do, he'd decided to check out the source of the repeated anomalies—and stumbled into Urahara's secret rendezvous.
"I'll keep observing for now..." Aizen decided. Only later would he act.
He too sought the Soul King Fragments—to forge a Hōgyoku of his own.
With Urahara having extracted a fragment from the Kuchiki clan's collection, it was the perfect opportunity.
Yet, having often heard his teacher praise Urahara's genius, Aizen couldn't help but grow curious. He wanted to see just how far Urahara had progressed.
"Let's grab a bite to eat."
"Okay!"
Aoba pulled Urahara along, hand in hand, as they left the area.
Meanwhile, Nanatsuki had obtained the Spiritual Detection Amplifier³ from Akon, a device capable of expanding the perception radius enough to help him locate Starrk.
"Captain..." Akon hesitated.
"What's wrong?" Nanatsuki asked gently.
"Third Seat Mayuri's locked himself in the lab..." Akon said worriedly. "He hasn't come out in over a month!"
"A whole month? Is he researching the Quincy?" Nanatsuki recalled that Mayuri had gathered quite a bit of Quincy-related material during the war.
"It's not the Quincy… It's because Nemuri No. 6⁴ has shown progress," Akon explained. "The embryonic development is far more stable than Nemuri No. 5—almost identical to a normal spiritual body. That's given Third Seat some hope. He's been holed up in the lab watching it grow. We tried telling him to rest, but he threw us out and locked the place down."
After more than two decades of effort, Mayuri's Nemuri Project had finally made some breakthroughs. Five generations of artificial spirit bodies had already been produced—but all had failed for various reasons.
Now, he was cultivating the sixth generation: Nemuri No. 6.
"That kind of lockdown wouldn't stop Vice-Captain Urahara," Nanatsuki remarked, remembering how Kisuke used to break into Mayuri's lab all the time.
"Vice-Captain... he said he understands Third Seat Mayuri and won't disturb him," Akon said hesitantly. "But… it's been a whole month."