The Department of Research and Development was a new branch, established only after Kisuke Urahara assumed his role. Here, one could find individuals even more bizarre than Hirako Shinji. Those with horns growing from their heads, others wearing strange golden masks while prancing around—these were the normal ones, still resembling humans. Naruto even spotted a green catfish-like creature working at a computer.
The way they treated Urahara Kisuke was peculiar. There was no deference typical of subordinates toward a captain; everyone was absorbed in their own tasks. Urahara paid them no mind either, leading Naruto and Yoruichi Shihōin to the lowest level of the Research and Development Bureau.
The area was vast, empty, and desolate. Naruto was surprised that such an enormous underground space existed, complete with a simulated sky—it felt like stepping into another world. He was also puzzled as to why he had been brought there. The environment resembled a training ground, and if the purpose was to examine his body, the upper levels with all the precision instruments seemed more suitable.
"Young Naruto, let me introduce you to this place," Urahara Kisuke said, spreading his arms with pride. "This is my first achievement after founding the Research and Development Bureau. In this place, we can evade all monitoring from Seireitei, including the restrictions imposed on us captains by the Central 46. Even a Bankai won't be detected by outsiders here."
Naruto frowned. This sounded even less like it was meant for "research."
"The seal on you is quite fascinating," Urahara continued, stepping closer. "Whether it's Shinigami, Hollow, or Quincy… Even compared to human spiritual mediums in the World of the Living, your power is fundamentally different."
Urahara paused, studying Naruto intently. Originally, he hadn't intended to get involved with Naruto, considering Unohana Retsu's request just a routine favor among colleagues. But as he delved deeper into the study of Naruto's seal and gathered information from Hirako Shinji, Urahara couldn't resist the urge to investigate the mystery surrounding Naruto. It bore a curious resemblance to a certain technology he was currently developing.
He went on, "The technique used in your seal only scratches the surface in terms of spiritual energy control, but it's ingeniously applied in body development. The results are comparable to our own techniques as Shinigami—a truly novel approach in a field we've yet to explore. Unfortunately, I only have Unohana-taichō's transcriptions…"
Naruto lifted his shirt slightly. "Do you want to take a look? I don't mind."
"No, no, no," Urahara shook his head rapidly. "The external form isn't important; I'm interested in how it operates internally. So… let's have a battle!"
Naruto blinked in confusion. "Huh?" The sudden shift in tone caught him off guard.
"Fight, and release your Zanpakutō during the battle," Urahara said, his voice brisk and full of enthusiasm. "Push yourself to the point of losing control. I'll record all the data to analyze how your spiritual energy interacts with the seal."
Naruto hesitated, but Yoruichi placed a hand on his head. "Kid, losing control means you're not yet familiar with your power. The more you use it, the better you'll understand it. And don't worry about hurting us—remember, Urahara might seem laid-back, but he's still a captain."
Urahara smiled. "And in this place, we're not constrained by any restrictions."
Naruto nodded, making up his mind. He drew his sword. "Alright then, Urahara-taichō, Yoruichi-taichō, I'm counting on you."
With that, he chanted the release command, unleashing the ominous and sinister spiritual energy of the Nine-Tails. Quickly, four tails formed, and he lost his sense of reason, descending into madness.
When Naruto awoke, he found himself in a hot spring. Yoruichi Shihōin was beside him, completely unbothered by her own nudity, though she bore a few bruises and scratches. Seeing him wake up, she cheerfully greeted him, "Yo, awake? You really hit hard, you know."
Yoruichi's nonchalance flustered Naruto, making him blush as he averted his gaze. He knew a similar technique to what Yoruichi seemed to be displaying, but seeing her like this was a different matter entirely. He wasn't used to such casual exposure.
Kisuke Urahara crouched beside the hot spring, his eyes gleaming with curiosity. "You've recovered quite well already. Think you can go another round of releasing?"
"I collected some interesting data, but it's still incomplete…"
Yoruichi splashed hot water at him in annoyance. "Give me a break, will you? My stamina doesn't match up to this brat's."
That day, Naruto lost control and released his power four times. Urahara was satisfied and arranged for Naruto to undergo such tests twice a week. As for payment, Naruto would receive all the research findings related to the seal, along with Yoruichi's *Hakuda* (hand-to-hand combat) training. Given that Yoruichi was the most skilled in hand-to-hand combat among the captains, her instruction greatly benefited Naruto.
Two months later, Urahara presented his first significant breakthrough: two additional spells layered onto Naruto's original seal. The results were impressive—Naruto could now retain his sanity while using four tails and only began to lose control at five tails.
The five-tail transformation brought Urahara an immense surprise. A white bone mask appeared on Naruto's face during the transformation. At first, Urahara thought it was a Hollow's mask, but after cutting off a piece with Yoruichi's help, he realized it wasn't. It was merely bone, not imbued with Hollow energy. Nonetheless, it sparked new ideas for his research.
However, the power of the spells seemed to have reached their limit. No matter how many auxiliary techniques Urahara added, they couldn't prevent Naruto from losing control at the five-tail stage. This frustrated Urahara, who was eager to see what six, seven, or even nine tails would look like.
The Zanpakutō known as the Nine-Tails far exceeded his expectations in strength. During this time, Yoruichi handled most of the sparring with Naruto, though Urahara occasionally joined in to gather data. They both concluded that Naruto's power at five tails was on par with the highest-ranked lieutenants. If he could reach six tails, his power might rival that of a newly appointed captain like Love Aikawa. By extrapolation, the full potential of his Shikai could place him among the top captains.
Despite his eagerness, Urahara knew when to hold back. Whenever Naruto showed signs of losing control or extending to a new tail, Urahara would seal off his spiritual energy flow, ensuring both Naruto's safety and their own.
In this cycle of training, study, and research, time flew by.
At the academy's training grounds, Aizen Sōsuke was instructing Naruto in Hadō techniques above level fifty when he suddenly remarked, "Graduation season is here again."
Naruto was momentarily stunned. "Yeah, graduation season…"
He looked into the distance, where cherry blossoms bloomed once more.
"Have you decided which division to join?" Aizen asked.
Naruto shook his head. "Isn't the school supposed to assign us after we apply?"
"That's for the average students," Aizen replied with a smile. "You're different—you're a genius. Even Hirako-taichō wants to recruit you."
Naruto thought about it. "The 5th Division, huh…"
"But more importantly," Aizen continued, changing the subject, "you're scheduled to go to the World of the Living with the sixth-year students for the Konsō (Soul Burial) practice soon, right?"
Naruto nodded, grinning widely. "Yes, Bōga-dono told me."
Konsō is a ceremony performed by Shinigami to guide souls to the Soul Society, a skill every Shinigami must master. Naruto was no exception, and he was looking forward to the field exercise in the World of the Living. Maybe it would help solve the mystery of why he kept inexplicably traveling between Konoha and the Soul Society.
The ceremony was simple, and the practical exercise in the World of the Living was more symbolic, representing the students' readiness to leave the academy and become full-fledged Shinigami.
"Good luck," Aizen said warmly. "But with training from Urahara-taichō and Yoruichi-taichō, I'm sure you'll have no problems."
Naruto's smile grew even brighter. "And thanks to your guidance too, Sōsuke! Without you, I'd never have learned all those advanced Kidō techniques!"
"Just call me Sōsuke," Aizen said kindly. "We're friends, after all. I'm only a vice-captain, not someone who can compare to those two captains. But Naruto-kun, your progress has been remarkable lately. Has something changed in your training?"
Naruto scratched his cheek. "Sorry, Sōsuke, but Urahara-taichō made me promise not to talk about it with anyone."
Aizen chuckled softly. "My apologies for prying. Treasure what you've learned from your captain, Naruto-kun."
(End of Chapter)