When it came to soul cultivation, Uchiha Kiyo's first instinct was to ponder over it deeply.
After all, the concept of soul training frequently appeared in various novels, and it presented a unique idea that Uchiha Kiyo could reference and potentially adapt.
"But… how exactly does this visualization process work? How is it executed? What's the mechanism that enables visualization to enhance the soul?"
With these thoughts spiraling, Kiyo's head began to throb.
Here he was—a shinobi with zero foundation in soul cultivation—contemplating the theoretical principles behind strengthening the soul through visualization. It was absurdly ambitious.
Visualization?
It felt too advanced. Uchiha Kiyo realized he needed to start with something simpler and progressively build towards a deeper understanding.
If strengthening the soul was possible, then it likely involved some form of nourishment. Essentially, the soul needed to "consume" something in order to grow stronger.
"Spiritual energy… could that be what the soul feeds on?"
But did spiritual energy actually have an impact on the soul?
The shinobi system had existed for over a millennium. If spiritual energy did directly affect the soul, someone would have discovered and refined that connection by now.
"Forget it, better to start by reviewing Orochimaru's data."
Stuck in a bottleneck with no clear direction, Uchiha Kiyo decided to examine Orochimaru's research first.
When it came to soul-related studies, Orochimaru was undoubtedly the foremost authority.
After all, the Soul Transfer Technique was developed solely by him. Not only that, but he managed to refine and perfect it over time, creating a technique that allowed repeated use.
The soul did degrade with each transfer, but Orochimaru's state showed that it was possible to recover from that loss—an insight that could be pivotal for Kiyo's research.
Land of Fire
Naruto followed Kakashi along the road back to Konoha.
This time, Naruto wasn't his usual upbeat self. Instead, he mulled over the words Uchiha Kiyo had spoken earlier.
"Kakashi-sensei, was what Uchiha Yun said... true?"
Kakashi could tell Naruto had been deeply affected. Who would've thought Uchiha Yun's revelations would shake him this much?
However, Kakashi had no room to be passive. As Naruto's mentor, it was his responsibility to guide and stabilize him emotionally.
"Naruto, there's some truth in Uchiha Yun's words, but you have to understand—his version is only part of a larger story. You can't judge everything based on that. He didn't mention how the Third Hokage's wife assisted during your mother's childbirth. Uchiha Yun left out many crucial details, and that's intentional. He's guiding your perception."
Naruto's expression showed some clarity, and although he wasn't as cheerful, the cloud over him began to lift. Still, the bright smile that usually lit up his face didn't return.
Kakashi sighed inwardly. The words had struck a nerve. He could only hope Naruto would recover with time.
More importantly, Kakashi recognized the growing threat—Uchiha Yun. The man knew too much. Just a few statements from him could be verified and turn hearts. He couldn't allow Naruto to encounter him again.
Upon their return to the village, Kakashi resolved to report this to Lady Tsunade. Precautions had to be taken—not just for Naruto, but for all of Konoha's shinobi.
Truthfully, the one Kakashi worried about most was Sasuke. Unlike Naruto, who had mentors like him, Jiraiya, and Tsunade, Sasuke's only anchor was revenge. If Uchiha Yun's influence reached him, there was no telling what direction Sasuke would take.
Sunagakure
Gaara had returned, and the reappearance of the Kazekage brought relief to many Sand shinobi.
Gaara had never relied heavily on Shukaku. So, even after losing the One-Tailed Beast, his strength remained virtually unaffected—something that deeply reassured the villagers.
Gaara was a genius in his own right. Many of the sand manipulation techniques he used were self-developed. As long as that ability remained, he was still powerful. Additionally, having inherited part of his father Rasa's magnetic physique and having been influenced by Shukaku since birth, Gaara's sand manipulation was nearly instinctual.
Thus, losing Shukaku didn't diminish his strength.
On the contrary, Gaara's power even seemed to grow. Without the interference of the tailed beast chakra, he now had better control over his own chakra reserves.
This wasn't exclusive to Gaara. For jinchūriki who had adequate chakra of their own and weren't overly reliant on tailed beast powers, losing their tailed beast didn't necessarily weaken them—except, of course, for perfect jinchūriki.
At the Kage level, a shinobi's power was already comparable to that of a tailed beast. While they might not win in a raw contest of power, they were still in the same tier.
In such cases, the tailed beast became more of a support asset—enhancing healing, chakra reserves, or battlefield transformation.
Yet, control over one's chakra remained the most crucial element of all. It was foundational and had the widest impact across all areas of combat.
At its core, the ninja system revolved around two things: chakra, and how to use it effectively.
With sufficient chakra, the next major step was maximizing its utility.
Dragon Veins – Uchiha Kiyo's Research Site
Uchiha Kiyo hadn't moved locations. He remained stationed at the Dragon Veins, continuing his research.
"Understood."
Orochimaru's materials were, as expected, profound—and highly useful.
"They confirm it. As long as the soul isn't extinguished, it can recover slowly over time, much like how the body restores energy through rest."
Orochimaru theorized that the soul, too, had an upper limit. Whether that limit was the peak it once reached or a fixed cap was unclear, but the fact remained: the soul could regenerate.
"What a fascinating concept... I didn't think Orochimaru recovered like this."
Each time Orochimaru performed a Soul Transfer, the soul was weakened. Theoretically, the soul could recover over time—but due to incompatibility between the soul and the host body, the fusion failed. That incomplete fusion impaired the soul's restoration process, creating a vicious cycle and leaving Orochimaru's soul flawed.
This flaw was one of the main reasons Uchiha Itachi was able to kill him.
Naturally, over time, Orochimaru made many improvements to the technique.
One of the keys appeared to be supplementing the soul's recovery—possibly with the host's own energy. But perhaps due to delays or missteps during the initial transfers, some of the damage was irreversible, though far less fatal than before.
"The Curse Mark… Orochimaru used it for soul recovery!"
While Orochimaru's documents didn't explicitly explain this, Uchiha Kiyo had enough knowledge to deduce it. Through combining the data, he inferred that the curse mark channeled natural energy into the soul.
"Natural energy restores the soul… and if the body can nourish the soul, it must house usable energy for it. Natural energy fits perfectly."
At first, Kiyo had fixated on spiritual energy due to its direct link to the soul. But he'd overlooked the diluted yet potent natural energy channeled through the body.
Natural energy was the foundation of all life in the shinobi world.
Who said natural energy only affected the body? It could act upon the body, but that didn't mean it was limited to it.
That difference was critical—whether energy only affected the body, or could affect the body and more.
"So… researching natural energy is the right path after all."
Kiyo raised his eyebrows in astonishment, but the conclusion made sense.
Many of his ongoing research topics were pointing toward natural energy. That alone proved how crucial the field was.
He also reflected on his research habits.
"Every time I study something unrelated, it somehow circles back to natural energy. But I never start from natural energy and explore outward. That's a mistake. My thinking is too compartmentalized."
That wasn't an effective research model. It showed his understanding of natural energy was still shallow and disconnected from other domains.
For the next half-month, Uchiha Kiyo devoted himself to refining soul cultivation techniques.
"Finally… progress."
Uchiha Kiyo, now dwelling in the future timeline, had numerous plans. He couldn't afford to be trapped forever in a single line of study. What was the point of time-travel if it was squandered solely on research?
That said, since he had already invested time into the study, he refused to stop without results. Besides, the time was originally allocated for studying the mechanics of temporal travel anyway—and that turned out to be simpler than expected.
"I didn't expect it… Natural energy is truly incredible."
The real key to enhancing the soul via natural energy was its volatile, untamed aspect.
Kiyo had theorized previously that all living beings—plants and animals—absorbed natural energy constantly. Though the amount was small, organisms also possessed the ability to "purify" it slowly...