A year passed in the blink of an eye.
The preparatory details for constructing the foundational transformation exceeded even Uchiha Kiyo's vast imagination. It wasn't that the process itself was overly complex—it was that he, as the first to forge this path independently, had to pioneer every single step from scratch. The intricacies of these steps, and their interconnectivity, were exactly what Uchiha Kiyo needed to carefully study.
Thankfully, the development and successful execution of his right eye's Mangekyō Sharingan technique came shortly after his return, significantly easing the process.
Takamagahara—Uchiha Kiyo's right eye ability—a Yin-Yang Release-based dōjutsu.
It granted the power to create all things devoid of life. Here, "life" specifically refers to sentient soul-bound existence. Lacking a soul does not mean the object lacks function. With full knowledge of cellular structures and biological operations, Kiyo could create living cells from nothing. Of course, without soul fusion, those cells lacked the drive for division or full autonomy.
Possibly influenced by his left eye's ability, the Yin-Yang Release of the right eye exhibited time-related characteristics. Any substance created through this pupil technique had its temporal flow manipulatable. Although individually the time-slowing effect was minimal, when paired with the left eye's temporal domain, the synergistic result was profound. For many of Uchiha Kiyo's experiments and procedures, this technique held immeasurable value.
Its role in the current foundation-building preparations was irreplaceable. While the generated cells lacked inherent division potential, under Kiyo's various transformation and stimulation methods, they could still evolve in accordance with natural principles—providing him with vast quantities of experimental material.
Moreover, the ability to alter time flow, while not directly critical to this stage, offered long-term strategic advantages that could not be dismissed.
After a full year, Uchiha Kiyo completed every necessary preparation for initiating the foundational transformation.
On this day, every single shadow clone halted their respective tasks, waiting silently for the coming transformation of the main body—the return to the innate—scheduled for the day after tomorrow.
Clear Island.
Uchiha Kiyo's isolated training ground.
Sitting cross-legged in a specialized chamber, Uchiha Kiyo opened his eyes and brushed off the thin layer of dust accumulated on his robes.
He had maintained this meditative state for half a month. In that time, he used his heightened perception to study every major organ and cellular structure within his body. He classified tissues based on function—those of value versus waste or impurities.
The process of "cleansing essence and cutting marrow" was a natural phase in immortal foundation building, but Kiyo, unfamiliar with the precise metaphysical mechanics used in the cultivation realms, chose to force the process through scientific and ninjutsu-based means.
Even if the body would've eventually undergone a spontaneous transformation, Kiyo chose not to risk it. Instead, he prepared meticulously, unwilling to waste such a pivotal opportunity.
He retrieved a large scroll and released it—hundreds of shadow clones materialized. These were no ordinary clones. Uchiha Kiyo had painstakingly created and sealed them over the course of the past year. Even their consciousnesses were sealed, preserving their full chakra reserves.
Their sole purpose was to provide pure energy for Uchiha Kiyo's breakthrough.
Yes—pure energy. By positioning the shadow clones near the main body before release, the returned chakra percentage could reach upwards of 80%. Every one of these clones had been created after Uchiha Kiyo had converted all his chakra into refined sage chakra—what he termed Gentle Sage Chakra. This unique energy, formed from purified natural energy fused with spiritual power, vastly surpassed standard chakra in both quality and potency.
Currently, the chakra within Uchiha Kiyo's main body was also composed entirely of this gentle sage variant.
"It's time," he muttered softly.
Taking a deep breath, he began.
A chakra barrier enveloped his body's surface, isolating the internal systems. Simultaneously, he activated his self-cultivation technique, guiding chakra back toward its natural origin—pure nature energy.
This was only the beginning.
Holding his breath, Kiyo deliberately initiated the destruction of specialized cells within his heart. A complete dismantling at the cellular level.
While his hands formed seals, external chakra flowed and activated a complex ninjutsu formation. This formation was one of Uchiha Kiyo's unique creations, built to directly manipulate natural energy rather than filtering it through chakra. A breakthrough he had theorized long ago during earlier experiments with self-cultivation, when chakra-based energy transfer had proven too inefficient.
This recent technique allowed him to bypass that bottleneck.
Activating his left eye's Mangekyō Sharingan, the time around his heart decelerated drastically—buying him the moments he needed.
Destruction… and reformation.
That was the cycle Uchiha Kiyo embraced to break through.
Without requiring cell division, he forcibly dismantled and reconstructed identical cell groups, bathing them repeatedly in gentle sage chakra. With every cycle, the cells' internal structures evolved.
He maintained this rigorous control for over an hour, breaking down and rebuilding every cell in his heart tenfold. By then, his face had grown visibly pale. Despite slowing time to extend his working window, the reduced blood flow to his heart began to take its toll on his stamina.
"Next—lungs."
The heart transformation complete, he moved on.
One organ at a time, guided by experience. Each transformation grew faster. From ten minutes for the lungs, to mere minutes for the liver, spleen, and kidneys.
Internal organs—complete. Next, the spinal cord. Then bones. Skull.
He ignored the vast majority of flesh-based cells, focusing solely on the structural and neural systems.
"Full-body circulation," he muttered.
The remaining gentle sage chakra flooded throughout his body, coating every cell with refined nourishment.
"Yang Release."
He infused the natural energy with Yang chakra transformation. The restructured cells, now imbued with vitality, began dividing—true division this time.
All useless, damaged, or inefficient cells were expelled alongside built-up toxins and impurities.
Uchiha Kiyo's body was covered in blood and waste material, a grotesque sign of the immense internal cleansing.
New stem cells divided and replaced damaged tissue. Flesh and muscle knit back together.
Kiyo's body bulked up, denser and stronger.
"One round is insufficient," he said, breathing heavily.
Despite undergoing multiple reconstructions, the stimulation on the cellular genetic level wasn't enough. At best, he had reached a point equivalent to the adaptation period experienced by kekkei genkai bearers. That wasn't acceptable.
Yet his chakra was nearly depleted.
As if anticipating his thoughts, two nearby shadow clones activated hand seals and released themselves. A torrent of chakra surged into Uchiha Kiyo, refilling him instantly.
He resumed the cycle.
Clone release. Cellular destruction. Reformation. Division. Again.
And again.
Despite the agony, Kiyo persisted. Over and over.
At last, he sensed a breakthrough.
The cells' energy-holding capacity had significantly increased. Their ability to circulate and purify natural energy had grown exponentially. Their natural affinity toward energy had matured.
He used chakra to guide a trace of natural energy through his body.
Then—the miracle.
Cells began autonomously absorbing and purifying natural energy. The process was rapid, smooth, and shockingly efficient.
Uchiha Kiyo smiled.
"It's done."
Now for the next stage.
Dissolving the chakra barrier around his body, he drew in natural energy directly from the environment.
His cells, though exhausted from repeated division, began absorbing this new influx ravenously.
"Let's see how far we can go."
He activated both the self-cultivation and soul-strengthening techniques simultaneously. Every single cell in his body consumed natural energy like a desert absorbing rainfall. Despite the immense influx, there were no signs of petrification or natural energy backlash.
His body had adapted.
Every bit of wild nature energy that entered was rapidly purified, assimilated, and stabilized. The days of fearing sage energy rejection might be over.
This was the Innate Body.
The body Uchiha Kiyo had dreamed of—a body that could absorb, filter, and harness natural energy directly without fear of being turned to stone. A body in complete harmony with nature.
As the natural energy flooded him, his vitality wasn't just restored—it grew.
The synchronization between his soul and body climbed higher and higher.
Until finally—he crossed a threshold.
His entire being felt as though it had been sublimated.
"This... is the soul?"
Suspended in a vast void, he saw a luminous, transparent form in the darkness. Somehow, he instinctively knew—this was his soul.
"So this is the Sea of Consciousness?"
Until now, Kiyo had only ever sensed his soul in its spiritualized state—never this clearly, never this intimately.
Fascinated, he murmured, "So this is the true soul."
But there was work yet to be done. This new domain of the soul could be explored later.
With a thought, Uchiha Kiyo exited the Sea of Consciousness and returned to his body.
He took a deep breath and silently analyzed the changes within him.
Uchiha Kiyo fell into contemplation...
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