Uchiha Clan Compound, Sasuke's underground laboratory.
On a fully equipped surgical table, Sasuke, fully armed, was meticulously studying the cells he had extracted from Yamato's body.
"Although Yamato's Wood Release is far inferior to the First Hokage's, his transplant is, in some respects, the truly perfect fusion."
Sasuke picked up the research report he had compiled on Yamato's cells and examined it closely.
Years ago, Uchiha Madara had bitten off a piece of Senju Hashirama's flesh while the latter was in Sage Mode, cultivated it, and transplanted it into his own body.
While that flesh was significantly purer than ordinary First Generation Cells, and the Wood Release it produced was nearly flawless, approaching Hashirama's peak power in life, Sasuke, viewing it from the perspective of a rigorous Medical Ninja, considered Madara's method—obtaining the Sage Body through something akin to growing a human-faced tumor—crude and primitive.
In contrast, the Yamato version of the transplant, born under the direction of the biological fanatic Orochimaru, though less powerful, Sasuke deemed a success.
First Generation Cells were injected into the bone marrow cavity of the test subject, replacing their original bone marrow stem cells.
Bone marrow stem cells possess several key characteristics: multidirectional differentiation potential, hematopoietic support, promotion of stem cell engraftment, immune regulation, and self-replication. They can differentiate into various tissue cells, including fat, bone, cartilage, muscle, tendons, ligaments, nerves, liver, cardiomyocytes, endothelial cells, and more.
As the primordial cells responsible for the human body's self-replication and multidirectional differentiation, bone marrow stem cells represent the origin of life—the fundamental units from which all human tissues and organs are derived.
Perhaps due to Yamato's unique constitution, his bone marrow transplant of First Generation Cells didn't trigger the rejection responses observed in other test subjects. Instead, his own stem cells and the First Generation Cells underwent a miraculous fusion.
Yamato's Wood Release abilities pale in comparison to those of the First Hokage, a disparity easily explained by factors beyond combat experience and raw power.
The various tissue cells differentiated from Yamato's bone marrow stem cells are not the original First Generation Cells. Consequently, they lack the First Hokage's overwhelming strength, representing instead "Yamato cells" with Wood Release capabilities—cells uniquely belonging to him.
For example, when Yamato was critically injured and lost a significant amount of blood, the new blood produced by his bone marrow stem cells consisted of his own cells, not the original First Generation Cells.
Yet, to Sasuke, this constitution—where all organs, bones, nerves, lymphatic system, tissue fluid, blood, fat, and everything else are produced and differentiated by the body itself—was essentially a weaker but perfect version of the Sage Body.
Uchiha Madara wasn't a Medical Ninja, nor did he possess the rigor of a Biological Researcher. His transplantation method was crude and pseudoscientific, yet it inexplicably succeeded.
This could only be attributed to some shady deal between Ashura and Indra.
"So during the Fourth Great Ninja War, it's easy to understand why Uchiha Obito and Yakushi Kabuto captured Yamato and implanted him in the Demonic Statue of the Outer Path—to enhance the White Zetsu with his cellular power," Sasuke murmured to himself, a look of understanding dawning in his eyes.
The White Zetsu already possessed First Generation Cells, so why capture Yamato?
Because the White Zetsu aren't truly human. They lack Yamato's continuous bone marrow blood-producing capacity.
Considering everything, it's a miracle Yamato wasn't drained dry back then.
Muttering this to himself, Sasuke picked up the research report in his hand and began reviewing it again.
"Although Yamato's transplant was relatively successful, I'll still need genuine, undiluted First Generation Cells in the future."
The Yamato cells Sasuke currently possessed were merely diluted First Generation Cells, and they were irreversibly altered.
While these cells retained the Wood Release power of the original First Generation Cells and were safer and more manageable, their quality and quantity fell far short of Sasuke's requirements.
Even Uchiha Madara, with his immense power, had taken decades to awaken the Rinnegan after transplanting original First Generation Cells.
If Sasuke were to rely on this weakened version of Wood Release cells, he couldn't imagine when he'd ever awaken the Rinnegan.
Three years!
The time Sasuke had before him was, at most, three years. Within that timeframe, he had to exhaust every means to awaken the Rinnegan.
Even if he failed to awaken the Rinnegan within three years, he absolutely had to achieve the peak strength once possessed by the First Hokage and Uchiha Madara.
"Still, it wasn't a complete loss," Sasuke concluded. "Though I still don't know exactly how Orochimaru performed the transplant back then, I've gleaned some of the underlying principles. This method seems to be the most suitable transplant technique for me."
While Uchiha Madara's transplant method undoubtedly granted immense power, the cells in his chest remained those of the First Hokage, not cells differentiated from his own body.
Sasuke aimed to replicate Yamato's approach, preserving the characteristics of First Generation Cells while generating his own unique cells—Sasuke's cells.
Setting aside the research report, Sasuke stepped forward and picked up a vial of crystal-clear, colorless liquid that shimmered with an eerie glow under the lamplight.
Hero's Water!
Though Sasuke hadn't encountered the chapter on Waterfall Village's Sacred Tree in his previous life, he had managed to uncover the tree's origins.
After sealing Ōtsutsuki Kaguya, remnants of the God Tree Ten-Tails persisted across the world for decades.
The Sage of Six Paths had dispatched Ashura and Indra specifically to manage these remnants.
It seemed the Sacred Tree of Takigakure had slipped through the cracks.
"The muscles, bones, nerves, and all other tissues of any living organism have a limited capacity, or rather, are bound by certain constraints."
"The Hero's Water doesn't so much amplify an organism's Chakra as it breaks through the shackles limiting the organism itself, unleashing its latent explosive power to the absolute maximum without causing physical harm."
"It's somewhat similar to the Eight Inner Gates and the Gene Lock I read about in those novels from my past life."
"Only by pushing the body to its absolute limits can one unleash a Chakra output tens of times greater than normal."
Sasuke murmured, gazing at the Hero's Water in his hand.
Through his recent research, he had begun to unravel the mystery behind the Hero's Water's ability to amplify human Chakra.
It seemed akin to a black technology-derived stimulant, optimizing biological tissues to the extreme and pushing an organism's latent explosive potential to its zenith.
Yet, merely calling it a stimulant would be inaccurate. Those who drink the Hero's Water experience a fundamental enhancement of their physical constitution as well.
"This is some application and reinforcement of Yang Release! It's just that the user's body can't withstand the backlash."
Sasuke concluded, "The Hero's Water itself strengthens the user's biological tissues, and during its release, it's similar to forbidden techniques like the Eight Inner Gates, which force the body's energy to explode to its absolute limit."
Silently summarizing his recent discoveries, Sasuke couldn't help but recall something else he'd seen on TV in his previous life:
The Meteorite from the Hoshigakure!
Many Naruto fans in his previous life speculated that this Meteorite was flesh and blood that had fallen from the Ten-Tails, even though that storyline was an original TV arc that aired in 2005 and 2006.
Back then, Kishimoto—who was notoriously late with his manga deadlines—reportedly hadn't even decided whether the Akatsuki's leader should be the Fourth Hokage or an original character.
Naturally, he hadn't given any thought to what might happen seven or eight years later.
Nor could he have imagined that the TV animation team would introduce a Meteorite that resembled the Ten-Tails' flesh and blood so early in the series.