Flooding someone's lungs with raw yang chakra could trigger respiratory alkalosis—but that was crude, obvious, and the success rate sucked. Subtle it was not.
After tweaking his method, Kenichi had taken a different route.
Now, he could let yang-nature chakra seep into the air around him, blending into the atmosphere. When people nearby breathed it in, it would quietly feed the cancer he'd planted in their lungs, making it grow worse and worse.
In theory, this technique had all the potential to evolve into a large-area killing jutsu.
For now, though, Kenichi wasn't aiming that high.
Right now, he just wanted to see what cancer did to a chunin.
"Sensei, look here—this subject's lungs are already showing early-stage lung cancer changes."
Kenichi's voice carried a barely concealed excitement. Just as he'd guessed, it didn't matter if the target was a civilian or a chunin.
As long as you were human.
As long as you needed your lungs to breathe.
You couldn't escape lung cancer's grip.
Early stages might not cripple someone in a fight.
But late stage?
Terminal stage?
Kenichi had visited relatives in the oncology ward in his previous life. Late and terminal cancer patients were… pitiful.
Their bodies couldn't support even simple movement.
Lying still hurt.
Every breath, every moment, was pain.
If his experiments succeeded, a shinobi fighting near him would slowly degrade—body weakening, stamina crumbling. The longer they stayed in his range, the worse they'd become.
"I read your report," Orochimaru said, eyes fixed on the monitor. "You tested that 'Cell Extraction Technique' on this condition, and it had no effect?"
"Yes, sensei." Kenichi nodded. "Cancer cells are still their own cells. They're not external toxins. The technique can't identify them as foreign."
He'd already pushed a few cancer cases to the medical team:
Early-stage patients had a small chance of recovery.
Mid-stage depended heavily on physical constitution.
Late-stage? Not a single successful cure.
Terminal stage… didn't even need to be discussed.
Of course, part of that was because the ninja world's understanding of cancer was practically zero.
"Continue," Orochimaru said. "I want to see the 'late stage' you talked about."
He'd noticed the chunin's gradually changing lungs as well. The similarity to Hashirama's cells was becoming hard to ignore.
Kenichi took a breath and went back to work.
At late stage, survival chances dropped sharply. There was basically no coming back from that.
As his yang chakra continued to pour specifically into the lung cancer cells, the chunin's lungs began to show clear, visible abnormalities. White, uneven depressions formed on the surface—massive tumor growths warping the organ.
"Too long," Orochimaru murmured, shaking his head before nodding again. "This takes far too much time, Kenichi. On a real battlefield, no one will stand there and let you pump chakra into them for this long."
He wasn't wrong.
From a pure combat perspective, the jutsu was painfully slow.
But as an assassination method? As a silent, delayed kill?
It had… potential.
For example—
A certain old man who loved smoking his pipe: the Third Hokage, Hiruzen Sarutobi.
"I know, sensei." Kenichi scratched his head.
Right now, Cancer Induction was still clumsy and limited. But if he could shorten the ramp-up time, increase efficiency, and perhaps find more ways to trigger different cancers…
Then the ceiling of this technique would skyrocket.
Lung cancer worked beautifully with nicotine.
But what about other tissues? Other organs?
He couldn't go organ by organ, trial-and-error, forever.
He needed something stronger.
In his previous life, when radiation was first discovered, it was treated like a miracle. There were even cosmetics infused with radium.
Only later did people realize: radiation causes cancer.
And by then, the damage was done.
So Kenichi's next idea was simple and terrifying:
If he could find radioactive elements in the ninja world…
If he could build a controllable source of radiation…
Then cancer would no longer be just a disease.
It would become a weapon system.
After getting a rough sense of the experiment's progress, Orochimaru didn't linger. Before leaving, he merely instructed Kenichi to keep detailed records of the chunin's symptoms and survival time.
Kenichi had planned to do that anyway.
Chunin-level test subjects were rare. Every second of data was precious.
When the session finally ended, he stripped off his lab coat and headed out to eat.
This time, he chose Ichiraku Ramen.
Ichiraku had been around for years, quietly watching generations of shinobi grow up. Back when Rin was still alive, she'd eaten here with Obito and Kakashi.
Kenichi dropped by occasionally. The taste really was good—better than the cheap shop he usually went to. The only downside was the price.
He'd even begun to suspect his usual place was cheaper precisely because their broth wasn't half as good as Ichiraku's.
He had just sat down when someone took a seat two spots away.
The silver hair was impossible to miss.
Kakashi Hatake.
Kenichi glanced sideways. Kakashi looked the same as ever—expression blank, presence quiet. But now he appeared and vanished around the village far more often.
Probably joined ANBU already… Kenichi guessed.
The Fourth Hokage was clearly trying to use endless missions to numb Kakashi's grief, to grind his heart back into working order.
Judging from the future, it worked… more or less.
Kamui, huh… Kenichi clicked his tongue inwardly.
The more he thought about it, the more he felt that space-time ability suited him perfectly. But right now, both Kamui eyes were in use—one with Kakashi, one with Obito.
Kakashi was approachable.
Obito… not so much.
And Kamui's power only fully blossomed when both eyes were together, sharing the same dimension.
Just imagining Obito in that empty space, getting randomly hit by kunai, shuriken, and explosive tags Kakashi tossed in over the years…
Kind of tragic, really.
And yet he never went to retrieve his other eye back.
True love, Kenichi thought dryly.
Kakashi slurped his noodles in silence.
Kenichi saw no point in slamming his own enthusiasm into a wall of dead-fish eyes, so he ate quietly as well.
By the time he finished, Kakashi was already gone.
Kenichi didn't care much either way. He paid his bill, took a toothpick between his teeth, and strolled slowly toward home.
"Rain Palace–senpai!"
The familiar shrill call made his temple twitch.
Anko Mitarashi.
Again.