Sakura wasn't aware that she had become quite famous. During the Konoha Crush, her feat of treating hundreds of injured shinobi over the course of a day and night had made her one of the most highly regarded medical ninja of the younger generation.
What made it even more interesting was the discovery by Konoha Hospital that Sakura wasn't even officially registered as a medical ninja.
In recent days, the hospital staff had visited Aoba's house countless times, hoping to recruit Sakura.
But Sakura was overwhelmed with the assignments Aoba had given her and was completely unaware of her newfound fame. She had no intention of working at Konoha Hospital.
"The Mystical Palm Technique isn't considered a top-tier medical jutsu, but its use requires the conversion of Yang-release chakra, and there's significant loss when transferring it into the patient's body.
This makes it a fairly chakra-intensive technique. Using it hundreds of times consecutively exceeds the limits of most ordinary ninja. Can you tell me how you managed it? Of course, if it's a personal secret technique, you're free to decline."
Tsunade was in a mixed mood. She could sense an immense chakra reserve within Sakura, a chakra that felt oddly familiar—it carried traces of Senju Hashirama's energy.
Her first thought was the possibility of Sakura being a product of the Hashirama cell experiments, perhaps even that Aoba himself was conducting such experiments in secret.
She wasn't entirely wrong. Aoba was indeed working on Hashirama cell research, though he had avoided direct human experimentation.
Tsunade had always opposed the experiments on Hashirama's cells. No one liked seeing their grandfather's body used for experiments. Her disgust with such practices was part of why she had distanced herself from Konoha.
"Ah, Hokage-sama, you mean this?" Sakura hesitated, causing Tsunade to assume she was unwilling to reveal the secret.
"No, it's not that. I just…" Sakura stammered.
At that moment, Aoba's voice came from the doorway.
"She hasn't been involved in the deeper aspects of the experiments yet, so it's hard for her to articulate an answer."
Tsunade turned to face Aoba.
"Aoba, you owe me an explanation today."
Tsunade had high hopes for Aoba. She needed a capable and resourceful assistant, but not one who would turn out to be another Orochimaru or Danzo.
"No explanation needed. I'll be upfront: the answer lies in the results of the Hashirama cell experiments. But the process may not be what you think. Follow me. Sakura, you come too—it's time to take your studies to the next level."
Aoba led the two into his underground laboratory.
The lab was nothing like what Tsunade remembered—it had grown significantly, its area at least five times larger than before.
Aoba had divided the lab into several sections. He took them to the outermost lab.
"I'm sure you're aware, Tsunade-sama, that Konoha has never stopped researching the First Hokage's cells. This may be uncomfortable for you, but I need to emphasize a fact: the First Hokage's cells represent a new era of potential."
Tsunade was momentarily stunned by the sight of the lab. It was unsettling, filled with jars containing twisted, malformed flesh.
The grotesque specimens caused Sakura to pause mid-step, clearly disturbed.
"These are failed cultivation attempts. Some still have their uses, so I've kept them. But this—this is the key," Aoba said, pointing at a set of peculiar garments.
Sakura's expression turned odd when she recognized the vest-like garments—she was wearing one herself. The reason she could continuously use the Mystical Palm Technique hundreds of times was because this vest provided her with a steady supply of chakra.
She had never realized that her vest was created in this lab.
Tsunade's sharper senses picked up on the vest's origins. She gently touched one and quickly understood its composition.
"This… Did you cultivate this using my grandfather's cells?"
"Exactly. These are chakra bio-vests, cultivated from the First Hokage's cells."
Sakura immediately felt uncomfortable upon hearing this. It dawned on her that the garment she wore was essentially made from the First Hokage's cells.
No wonder it felt so strange. Realizing that she was wearing what amounted to a living "human skin vest" made her skin crawl.
While Sakura grappled with her unease, Tsunade and Aoba continued their discussion.
"You didn't conduct direct cell transplants on humans. Instead, you developed support tools using my grandfather's cells?" Tsunade asked.
"Not just an attempt—I've already produced a working prototype. It wasn't easy, though. The First Hokage's cells have incredibly high regenerative properties, making them prone to uncontrollable growth.
Shaping them into usable forms was a lengthy process. Only after significant trial and error did I discover a relatively effective method."
"Controlled cultivation?" Tsunade's question caught Aoba off guard—she had guessed correctly.
"Exactly. If you let Hashirama cells grow freely, they form chaotic, Cthulhu-like flesh masses. To shape and control them, I had to employ precise cultivation techniques.
Sakura's chakra vest wasn't purely grown from Hashirama's cells. It was created by combining her own cells with Hashirama's. After dozens of failures, we finally succeeded."
The failures were due to two main reasons: the overwhelming strength of Hashirama's cells compared to Sakura's weaker ones, and Aoba's initial lack of experience. After experimenting with cells from Sakura, Kakashi, and himself, he had perfected the technique.
However, the method had a major flaw, it wasn't universally applicable.
After expanding his research to include various biological samples, Aoba reached an uncomfortable conclusion: most civilian ninja cells were incompatible with this cultivation process.
In contrast, ninja from major clans had success rates ten times higher than civilians.
Faced with this disparity, Aoba chose to keep the technology hidden.
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Currently on Chapter 160 - Uncovering His Mangekyō Sharingan