"This really shows the difference between a ninja's body and a civilian's…"
Kenichi Amamiya watched the rise and fall of the chest in front of him, genuinely impressed.
To observe more clearly, he'd already removed the ribs.
Yes—removed. One by one.
It went without saying that this pretty much guaranteed the subject wasn't going to live very long, but Kenichi didn't really care anymore.
Moments ago, he'd successfully triggered early-stage lung cancer in this ninja's body. The first malignant cells had appeared and begun to cluster. The man's body was already starting to change.
"Cough… cough, cough…!"
The test subject doubled over in a fit of coughing, chest trembling in raw pain.
Kenichi calmly increased the flow of yang chakra.
He was now attempting something new: instead of flooding the whole lung, he tried to inject that warm, violent energy directly into the already-formed cancer cells.
Cancer cells were nothing more than rogue citizens—mutated cells gone bad. They devoured nutrients like bandits, multiplying without restraint. Now, with yang chakra as pure life fuel, they didn't just grow—
They exploded.
Under Kenichi's eyes, the rate of spread visibly accelerated. The man's coughing turned wet, crimson spraying across the cloth. His breathing grew ragged, then labored. Each inhale sounded like someone drowning on dry land.
"My theory was right. Yang chakra can stimulate cancer cell growth and create an artificial cancer in the target's body," Kenichi murmured, a hint of satisfaction in his voice.
He had taken the first real step.
As long as he could standardize the process, control the flow, and test the success rate, he would have done it:
Created a completely original, custom-made ninjutsu.
"…There is that medical technique, Cellular Extraction or whatever it's called. They use it to draw out poison," he mused, rubbing his chin. "But it shouldn't affect my jutsu. Not directly."
By now, he could accurately inject yang chakra straight into the cancer cluster. On top of that, he'd already noticed signs of metastasis—migration. The corrupted cells were starting to spread beyond the lungs.
In his previous world, that was the point where doctors stopped using hopeful words and quietly mentioned "arrangements."
Kenichi stitched the man's chest back together with practiced hands, like closing an experiment notebook.
Then he shoved the subject off to the medical team stationed in the base.
"Patch him up if you can," he said. "He's useful."
He wanted to see whether the shinobi world had any real answer to cancer.
If they could cure it, his technique's practical value would drop sharply.
If they couldn't…
Then he'd just created something worthy of the "Forbidden Jutsu" shelf.
"You're done with your experiment?"
When Kenichi went looking for his teacher, he found Orochimaru's table already occupied—two ninjas lay there, lifeless and limp.
The air was different too.
Under the smell of blood and preservatives, there was a faint, dry scent—dust and earth, stirred up from nowhere.
On the stone surface, Kenichi could still see traces of strange ash and a half-smudged formula.
Impure World Reincarnation…?
His mind immediately connected the dots.
"Yes, Sensei. The experiment made some progress," Kenichi replied, slipping seamlessly into his ordinary tone. "I sent the subject to the medical unit to see if they're able to treat him."
Orochimaru nodded slightly, expression unreadable.
"Don't neglect your ninjutsu training. That is still the foundation of our existence as shinobi," he reminded him calmly.
Orochimaru's management style was simple: once he decided to use someone, he gave them room to work. No micromanaging. No needless suspicion.
"Trust those you use, don't use those you can't trust."
He was cold, but he wasn't a small man.
"Of course, Sensei."
Kenichi nodded.
He'd already drawn up a schedule for himself:
Morning—body training and ninjutsu.
Daytime—Orochimaru's assigned tasks.
Night—research and refinement of his "cancer-style" ninjutsu.
Ever since he'd gained the Sage Body of Hashirama Senju, an ocean of yang chakra churned inside him. That vast vitality was both his greatest weapon and his biggest headache.
If only he'd gained Wood Release on top of it.
That part still stung.
"Wood Release would've been perfect… then I could have gone after the Tailed Beasts," he thought, almost drooling at the idea.
Massive living chakra constructs, each with unique abilities and nuclear-level destructive power. In the later years of the story they looked like punching bags, but at their core, they were still terrifying.
There was a reason every hidden village treated them like strategic weapons.
Like living warheads.
"I have a jutsu I intend to teach you."
Orochimaru reclined in his chair, voice casual. But the moment he spoke, Kenichi felt his own heart skip a beat.
The corpses. The dust. The residue on the table.
There was only one technique that matched that scene.
Impure World Reincarnation.
"…Is it the Lightning Body techniques from the Hidden Cloud, Sensei?" Kenichi asked, letting his eyes light up like an eager student.
With his current "rank," he had no business touching Konoha's forbidden scrolls.
It would be suspicious if he didn't at least pretend to misunderstand.
"No," Orochimaru replied. "This is… something different. A powerful, but very troublesome, forbidden jutsu."
He tossed a scroll at Kenichi.
The boy caught it and unrolled it.
Four characters stared back at him:
Impure World Reincarnation.
Even though he had already guessed, seeing the name written out still made his pulse hammer.
This was one of the jutsu of the Naruto world.
A technique that could warp the balance of war.
"…Thoughts?" Orochimaru sipped his tea, watching Kenichi closely. He wanted to see how his chosen disciple understood this technique.
"It's incredibly strong," Kenichi said honestly. "And incredibly dangerous. Extremely practical in war… but once you use it, you're guaranteed to make enemies."
Orochimaru's lips curled.
"Why do you say that?"
"Because it brings the dead back," Kenichi answered bluntly. "It's a direct insult to the dead… and to the living who remember them. Anyone with a brain will hate the user on principle."
He didn't believe for a second that Orochimaru hadn't already thought of this.
This was Orochimaru. If even Kenichi could see it, his teacher obviously had.
"But," Kenichi continued, shrugging, "it's also ridiculously powerful. If the revived retain even a portion of their original strength, they become terrifying pieces on the board. They don't tire, they don't fear death, they can't truly be killed. They're pure, disposable war assets."
He couldn't help thinking:
If, during the Nine-Tails' attack on the village, someone had summoned the First and Second Hokage with Impure World Reincarnation…
What would the Nine-Tails have done then?
"What if I teach it to you?" Orochimaru asked suddenly, eyes narrowing with interest. "Do you have the courage to learn it?"
Kenichi didn't even hesitate.
"Of course I do," he said, eyes shining. "It's a forbidden jutsu, isn't it? I'd be an idiot not to learn it."
Whatever people might say about him in the future—
One thing was certain:
Kenichi Amamiya was definitely not an idiot.