However, in reality, Yang Release chakra does indeed possess similar effects; the Mystical Palm Technique, a staple of medical ninjutsu, utilizes Yang chakra to stimulate cellular regeneration and accelerate healing.
Of course, an excessive amount of Yang chakra can disrupt the body's natural energy circulation, potentially leading to uncontrolled tissue growth or system overload—sometimes resulting in unconsciousness or even death.
Previously, Ryujin Kenichi had nearly killed that illegitimate child of the Hyūga clan several times due to miscalculations in chakra application.
Orochimaru observed his disciple with a hint of curiosity. "What do you plan to research this time?" he asked, knowing all too well that Kenichi always had strange, if not outright disturbing, ideas.
Kenichi responded with a bright, innocent smile. "Sensei, I just want to study that previous case a bit more."
How could he possibly have bad intentions? It wasn't as if he wanted to weaponize chakra to induce lung failure in his enemies, right?
Orochimaru's expression flickered with amusement and mild wariness. He understood precisely which case Kenichi was referring to and couldn't help but glance at him thoughtfully. His disciple possessed an unsettling darkness beneath that cheerful demeanor.
Indeed, taking him away from this decaying village had been the right decision.
At that moment, Kenichi was already formulating his plans. Since he would soon defect from Konoha alongside Orochimaru-sensei, he would need a new laboratory. But why should he build it himself?
Orochimaru-sensei was wealthy. It wouldn't be a problem to have him fund a fully equipped research facility, right?
After acquiring the necessary supplies from his teacher, Kenichi retreated into the lab to continue his experiments.
"Hmm, the cigarettes I bought last time are almost gone. I should restock soon," he murmured absentmindedly, stroking his chin. Then, without much thought, he roughly channeled chakra into the test subject before him.
Since this one was still alive—albeit missing a hand—Kenichi had little concern about whether the process would be too damaging. Without the need for restraint, his methods became even bolder.
"…What exactly are you doing?"
Orochimaru's voice cut through the silence as he entered the laboratory, his golden eyes narrowing at the sight before him. His expression hovered somewhere between intrigue and exasperation.
"An experiment, of course," Kenichi replied nonchalantly, as if stating the obvious.
Orochimaru pinched the bridge of his nose.
"Then tell me—why have you cut open his chest while he's still alive?"
Kenichi barely spared his teacher a glance. "To observe more carefully, of course."
Since the skin obstructed direct visualization, he had simply split it open from the middle. And truth be told, this method was proving quite effective. Now, he could accurately monitor the effects of nicotine-laced chakra on lung tissue in real-time.
Well, if the subject had been a smoker to begin with, this step would have been even simpler.
Orochimaru exhaled through his nose. "…Fine."
With an air of mild resignation, he turned and left.
Kenichi watched him go, then refocused on his work. Success was within reach.
Research Notes:
[Entry Log: Another test subject has been expended. However, all of this is worthwhile. Now, even without dissection, I can precisely control nicotine's effects on lung tissue.]
[The only issue remaining: how to refine the application of Yang Release chakra to specific cell types. Current tests result in excessive stimulation of pulmonary activity.]
[Wait—after prolonged exposure, the subject's heart rate has increased abnormally. The involuntary muscle spasms and paleness indicate a respiratory syndrome—perhaps hyperventilation-induced alkalosis?]
Kenichi set his pen down, observing the subject with interest.
Their heartbeat had become erratic. Their lips twitched involuntarily. Their complexion had turned sickly pale. Kenichi swiftly deduced that excessive pulmonary stimulation had triggered a respiratory imbalance.
An unintended side effect, but a fascinating one nonetheless.
He tapped his fingers against the desk, deep in thought.
"For a shinobi, respiratory alkalosis shouldn't pose a major issue… but what if Yang Release chakra were applied directly to the heart?"
The idea intrigued him. It called for further testing.
And, fortunately, he still had plenty of test subjects to spare.
As expected, they didn't survive.
The silent janitors within the laboratory moved efficiently, dragging the bodies away with practiced ease. They no longer reacted to the work—numbed by repetition.
They observed the dimly lit laboratory, eyes locked on the young man working inside. Even seasoned shinobi among them couldn't suppress the shiver running down their spines. This guy… he seemed even more terrifying than Orochimaru-sama.
Ryujin Kenichi, however, remained oblivious to the psychological scars he was leaving on those around him. His mind was occupied with calculations, theories, and—most importantly—progress.
His latest experiment had proven successful. The excessive infusion of Yang-release chakra had precisely the effect he predicted. The heart, overstimulated to the point of extreme hyperactivity, eventually fell into uncontrollable tachycardia—resulting in sudden cardiac failure. A silent, invisible death.
"Not bad," Kenichi murmured to himself, scrutinizing his latest results.
But almost immediately, he shook his head. "Still impractical. Shinobi aren't idiots."
This technique might have been an ideal silent assassination method in another world, but here, in the world of ninjas, it was a different story. No trained shinobi would just stand there and allow someone to forcibly inject their body with foreign chakra. Unless they were completely immobilized, this method was useless against anyone competent.
Of course, it might still work on civilians, but Kenichi dismissed that thought. If he were targeting civilians, why go through all this trouble? A kunai to the throat was far simpler.
No, for this to be effective, he needed a way to rapidly inject high volumes of chakra into a target's body—faster than they could react or defend against. A delivery system. That was the real challenge.
And, naturally, to refine the process, he needed test subjects. Proper test subjects.
"For the advancement of science and ninjutsu," Kenichi muttered as he strode purposefully toward his mentor's chambers.
Orochimaru's experiments had provided him with an array of test subjects, but thus far, they had all been civilians—utterly useless for fine-tuning his research. Perhaps his master assumed that Kenichi's studies didn't require shinobi-grade specimens.
But he did.
"...Aren't those civilians enough?" Orochimaru's voice was laced with something between amusement and exasperation as he peered at his disciple. Even he was beginning to find Kenichi's consumption rate of experimental materials excessive.
"Sensei, you of all people understand the difference," Kenichi replied smoothly, carefully choosing his words. "Ordinary people and shinobi are fundamentally different—because of chakra."
Chakra was the defining force of this world. It separated the weak from the powerful, the mundane from the extraordinary. Any serious research into biological enhancements or ninjutsu development had to account for chakra's unique influence.
Orochimaru exhaled through his nose, rubbing his temple in thought.
"...I have a Genin. Use them sparingly," he finally relented, though a gleam of curiosity flashed in his serpentine eyes.
He, too, was interested in these strange cells Kenichi had been working with—cells that bore an uncanny resemblance to those of the First Hokage.,