Mayuri Kurotsuchi was urgent—and eager.
Though there wasn't much left to study about the Summoning Technique, and it wasn't particularly difficult, as a "research topic," it didn't hold much value.
But—
It offered a glimpse into a foreign and massive system of knowledge—just the tip of the iceberg.
And no "scientist" could resist the allure of knowledge.
"I have a challenge for you," Naruto thought for a moment, lifting his hand from the scroll. "Wait here."
He got up and left. Not long after, he returned holding a rabbit.
Mayuri narrowed his eyes.
Though the Soul Society was a world of the dead, it still had a functioning ecosystem—animals naturally existed.
But…
A rabbit? As a research subject?
His own research always began with "souls."
"I've placed a seal inside this rabbit," Naruto said as he set it on the table. "It holds a stored force within."
"I want you, Captain Mayuri, to extract that force by breaking the seal—without harming the rabbit's life."
Earlier, Naruto had temporarily turned the rabbit into a kind of jinchūriki.
"One rabbit's life," Mayuri sneered. "Captain Uzumaki, how merciful of you."
"However…"
"This seal—it's related to you, isn't it?"
Naruto replied softly, "Captain Urahara wouldn't ask pointless questions unrelated to research."
Mayuri clicked his tongue louder.
"Oh, right. Just so you know," Naruto tilted his head at him. "I don't have much hope you'll succeed."
"After all—"
"Even Captain Urahara couldn't do it."
Mayuri's aura immediately intensified, turning sharp and hostile. "Captain Uzumaki sure trusts that man."
"If he were truly capable, he wouldn't have scurried away from the Soul Society like a rat."
"He couldn't do it—but that doesn't mean I can't."
He grabbed the rabbit by its ears. "Wait and see, Captain Uzumaki. But next time… what I'll ask for won't be this simple."
"You're welcome to come back anytime to get a fresh rabbit," Naruto replied cheerfully as Mayuri stormed off.
Watching his retreating figure, Naruto mused.
Kisuke Urahara had never actually tried to break the Four Symbols Seal.
He had just said a few casual words.
Still, leveraging the "competitive spirit" between people sure was effective for motivation.
He picked up the scroll and resumed reading.
Just the first page already impressed him. Urahara's judgment had been right—Mayuri was indeed smart and very capable.
He had modified the Summoning Technique to be performed using Kido.
The difficulty wasn't high—around the level of a Binding Spell numbered in the twenties or thirties.
He had also simplified the "technique," making it even more streamlined.
Furthermore…
In the next book—
He had theorized a Reverse Summoning Technique, and by combining it with Shunpo, he developed a method to use the summoning formula for rapid spatial movement within the same space.
However, as only a year had passed, the technique remained incomplete.
Mayuri admitted its flaws quite openly in the book. Though it technically moved through space, the activation time was too long—undermining the whole point of "teleportation."
Moreover, it was extremely difficult to learn.
It required not only delicate control over spiritual energy but also exceptional reflexes.
And Mayuri wasn't particularly keen on this kind of power. Since further research would require a huge time investment, he had stopped there. But… he did write that if Naruto was interested, and willing to offer something Mayuri wanted, he'd consider continuing the research.
Truly worthy of Kisuke Urahara's recognition.
These books provided great insight to Naruto.
The long lifespans of Shinigami often made their lives dull and repetitive.
Naruto's daily routine involved handling squad affairs and repeatedly researching the Four Symbols Seal and Dead Demon Consuming Seal.
Now and then, the Nine-Tails would grumble, blaming Minato for sealing its other half—leaving it unable to practice Bankai.
Sometimes Mayuri would show up with a scowl, demanding a new rabbit.
Breaking the Four Symbols Seal was extremely difficult.
The sealer only had to place it. The one unsealing had far more to consider.
Before he knew it, cherry blossom season had returned.
Aizen Sōsuke came to visit.
After exchanging greetings—
"Nothing urgent lately, right, Naruto-kun?" Aizen asked.
Naruto shook his head.
"Would you like to attend the entrance ceremony for the Shinō Academy?" Aizen invited him.
Naruto paused, glancing out the window. "It's that time of year again, huh."
"But what made you think to invite me, Sōsuke?"
Aizen smiled. "You know me, Naruto-kun. I attend the ceremony every year."
"And every year, I hear the students talk about wanting to see Captain Naruto Uzumaki—the youngest captain."
"They're always so excited."
"I just wanted to grant that wish, so I came to invite you."
Naruto nodded.
His Kagura Shingan told him Aizen's emotion during that speech was genuine.
"Well, since you're asking so sincerely—I have no reason to refuse," Naruto agreed.
Aizen looked up, joining him in gazing out the window. A cherry tree stood in the courtyard of the 7th Division. A breeze swept through, scattering petals like rain.
"That's wonderful, Naruto-kun."
Then something occurred to him. He suddenly turned back.
"If only the Soul Society could always remain like this."
Naruto froze.
Kagura Shingan told him—that sentence was a lie.
The entrance ceremony came quickly.
With two captains in attendance, Headmaster Bogan was beaming.
Naruto was used to such grand occasions and recited the speech he'd prepared the night before.
Once he finished, Aizen took the stage.
His speech differed from previous years—as if he wrote a new one for every batch of freshmen.
At the end—
Aizen smiled at the crowd. "May you all become exceptional Shinigami."
"And every year, I offer a display of my Zanpakutō's release to bless the new students."
"But this year, Captain Uzumaki is here too."
He turned toward the golden-haired figure in the crowd. "Naruto-kun, would you like to demonstrate your release?"
Naruto shook his head. His sword wasn't suitable for show.
Aizen raised a hand to his own blade. "Then I shall proceed as usual."
He drew it and began the release chant:
"Shatter—Kyōka Suigetsu."
A mirage of flowing water formed, projecting illusory images.
The students gasped in awe.
Naruto's eyes saw through the illusion. Smiling, he gazed at Aizen standing on the podium—this level of Genjutsu no longer affected him.
"Every Zanpakutō has different abilities," Aizen said gently. "This is mine."
After a moment, he sheathed the sword.
Headmaster Bogan scratched his head.
Something felt missing this year.
Only after seeing off the two captains and scheduling a get-together at a tavern did it hit him—
Captain Aizen had left out his usual closing words.
He always used to explain his Zanpakutō's specific ability—a water-type blade with rare illusion capabilities in the Soul Society.
But not this year.
Did he forget?
Or perhaps, because the two captains' speeches ran long, he skipped that part?
Back at the squad barracks—
Naruto couldn't let go of that one lie Aizen had said.
Still… that seemed to be the only lie.
Whether it was during the speech or in daily interactions, Aizen remained the same sincere and gentle captain.
Tōsen Kaname was also under observation.
He still refused to train with others and would vanish as soon as practice ended.
But Naruto had learned from the 9th Division members that Tōsen's Zanpakutō's Shikai was called Suzumushi—and it had hypnotic effects.
Hypnosis. A very concerning ability.
Though Naruto knew its effects, he hadn't yet figured out how it worked.
Was it activated through visual contact?
Or another method?
While continuing to monitor them, Naruto resumed his research.
He had made significant progress with the Dead Demon Consuming Seal.
Thanks to the scroll Orochimaru had given him, along with a complete version of the technique, he'd managed to reverse-engineer a method to undo the seal.
It required finding the demon's "contract item," using it to summon the Shinigami, and then slitting its belly open to release the trapped souls.
Fragmented souls would return to their bodies.
Dead souls would return to the Pure Land.
While Naruto made good progress, Mayuri was having a harder time.
Releasing a jinchūriki's power without harming the host was a significant challenge.
Still, there had been major developments.
From being unable to keep the rabbit alive, Mayuri had advanced to the point where the rabbit could now survive for up to a week after the power was released.
But… the lifespan loss was too severe. Neither Naruto nor Mayuri could accept that.
Another year passed.
Naruto was working at the squad office when—
"Captain!" Vice-Captain Kotetsu Isane burst in urgently. "A hostile intruder has forcefully broken through the Seireitei's Blue Stream Gate! He's already defeated several seated officers—but no deaths yet."
Naruto stood. "Intruder?"
"He's a long-haired man with black hair—and he's carrying a little pink-haired girl on his shoulder," Kotetsu reported. "He's extremely strong."
"We haven't even been able to force him to release his Zanpakutō."
(End of Chapter)