Early the next morning, at the Fifth Squad barracks.
Aizen watched Naraku Sora from a short distance with great interest, his focus almost entirely concentrated on the man's hands.
Basic Kido patterns, a surge of abundant Reiatsu, and that sharp edge belonging exclusively to Zanjutsu.
Every time Aizen thought Naraku Sora's upper limit had been reached, this fellow would always jump out and pull off some wild new trick.
"If it were merely a matter of attaching Kido to a Zanpakutō and using it as a medium to release it, perhaps it could only be considered the development of yet another new Kido."
Aizen spoke eloquently. Despite having graduated from the Spiritual Arts Academy not long ago, there were truly few people who could surpass his achievements in the field of Kido. And this was under the condition that he did not wish to reveal his true strength.
"One can refer to Hadō No. 78, Zankawarun; its form of expression is extremely similar to Zanjutsu."
Speaking to this point, Aizen pondered for a moment, the corners of his mouth turning upward.
"Like other Kido, every detail of Zankawarun—from the starting posture to the swinging strike—is a ritual that constitutes a complete Kido. It can be understood as an incantation."
"Similarly, experts can release Zankawarun through other postures. This can be understood as another type of Eishōhaki."
Naraku Sora realized. Information regarding relevant Kido naturally surfaced in his mind. If he remembered correctly, he seemed to have a "cheap" senior brother who was quite proficient in this Kido, though unfortunately, it hadn't caused any particularly effective damage in battle.
"But you are different, Sora."
Aizen hesitated slightly, seemingly feeling that such an address was perhaps a bit too intimate, but for his current persona, it seemed he had no choice.
"This Kido-Swordsmanship you've developed—let us call it that for now."
"It nearly perfectly achieves the fusion of Kido and Zanjutsu, breaking the boundaries between the two and allowing it to possess two completely different characteristics simultaneously."
"To complete such a technique is enough to leave one's name in the history of the Soul Society."
Naraku Sora grinned. "Where, where? Just a bit of luck, pure luck."
Aizen pursed his lips, a trace of complexity appearing in his gaze. He had originally thought this fellow came to find him today to ask for assistance in training. He hadn't expected Naraku Sora to pull out such a world-shaking technique.
He had thought the gap between the two of them would grow larger with the passage of time until it was no longer visible. Yet, not long after graduation, that distance had suddenly shrunk by a massive margin.
Aizen sometimes even wondered if he had become so immersed in handling paperwork lately that he had neglected his training, allowing this fellow to catch up. But on second thought, what normal Soul Reaper was as ridiculous as Naraku Sora?
Clearly possessing only Rank 10 spiritual power, yet he could fight upward against the grain, slashing until a Soul Reaper with Rank 6 spiritual power was breathless.
Wait—
Aizen's pupils constricted slightly, a flash of shock passing through his eyes.
Naraku Sora's Reiatsu...
Rank 7?!
Even though Naraku Sora did not fully display it, one could still detect something from the leaking Reiatsu when he used that self-created technique. Aizen considered his own talent in Reiatsu to be decent, but even he didn't have such an exaggerated rate of improvement, did he?
In just a few days, he had leaped from Rank 10 to Rank 7. If this momentum continued, he might actually end up replacing the Head Captain.
How long did it take Aizen himself to go from Rank 10 to Rank 7? Was it one month or two? Although no Soul Reaper with greater talent than himself could be found in the history of the Soul Society, compared to the guy in front of him, he felt... rather average, didn't he?
While Aizen was experiencing this internal conflict, Naraku Sora grinned and suddenly said:
"By the way, Sōsuke, how about I teach this to you? You can help me perfect it."
Aizen: "?"
"Have you not woken up yet?"
"Member Aizen, I am very awake."
"If you were awake, you wouldn't say such nonsense," Aizen said with a trace of helplessness on his face as he explained. "To say it without exaggeration, fusing Zanjutsu and Kido is a pioneering feat."
"Even if you founded a new school, it wouldn't be excessive at all."
"For example, the reason the Head Captain holds his current position, besides his own formidable strength, is inextricably linked to the Genryū school he founded."
"Or rather, the two complement each other. Genryū was also Head Captain Yamamoto's early foundation for establishing himself."
"It was because of the existence of Genryū that such a group of people gathered around him, leading to the original Gotei 13."
"And yet here you are, saying you want to teach your life's blood to someone else."
Naraku Sora laughed, sounding quite indifferent. "Just consider it an early investment. When you make it big in the future, Sōsuke, just don't forget to give your good brother a hand."
"Besides, aren't I asking you to help me perfect it?"
Aizen froze for a moment, completely not expecting the fellow to answer this way.
"Alright, stop standing there in a daze."
"Let's start from the most basic Zanjutsu."
...
...
Because he was not proficient in certain technical terms, Naraku Sora would generally substitute them with phrases like "first do this, then do that" during the teaching. If that didn't work, he would demonstrate it personally.
Clearly, this teaching method was not at all suitable for any other normal Soul Reaper. Only Aizen, who understood Naraku Sora relatively well, could quickly grasp his meaning, comprehend it, and convert the teaching content into his own.
However, this teaching process did indeed make Naraku Sora inexplicably think of Naruto Uzumaki and Konohamaru from the neighboring village. Speaking of which, Konohamaru, who could learn the Rasengan taught by Naruto, was truly a genius.
Just as the two were discussing whether higher-numbered Kido could be integrated, a Soul Reaper suddenly burst into the dojo.
"Ninth Seat Aizen, an emergency mobilization order."
The newcomer was panting, his face full of anxiety as he held the mission warrant high.
"The Soul Reaper responsible for managing Mount Koifushi in the third district of West Rukongai has gone missing without reason. When he was supposed to report his mission today, he didn't show up at all."
Hearing this, Aizen frowned and subconsciously glanced at Naraku Sora beside him.
"I understand."
"The mission is urgent. Please depart immediately."
After giving the instructions, the messenger Soul Reaper hurried away. Judging by his disappearing figure, there were likely other missions he needed to deliver.
"Please be sure to take me along!"
Just as Aizen was about to speak, his words were choked back by someone.
"The thing I can't stand most is those who violate the laws and act willfully."
Naraku Sora looked excited, eager to give it a try.
Aizen put away the bamboo swords scattered in the dojo and said expressionlessly:
"The disappearance of a Soul Reaper responsible for a fixed area is not common. Once it happens, it is very likely to be an extremely serious incident."
"This mission will very likely involve accidents."
So...
He looked up and said calmly, "Be careful."