Chapter 97: Genjutsu – Sensory Deprivation Technique
What is the principle behind genjutsu?
It works by flowing illusionary chakra into another person's body and reaching their brain, influencing it to trap the target inside an illusion.
Essentially, it feeds the brain false information—either by injecting or prompting it—thus confusing perception, and then misleading the sensory feedback transmitted by the brain to the body.
The key lies in input and output of information.
Information input allows the illusion to invade.
Information output makes everything within the illusion feel real to the target.
In fact, nearly all genjutsu—whether visual, tactile, or auditory—manipulate these two pathways.
Darkness Technique (Kokuangyo no Jutsu) follows this same principle.
But it's also fundamentally different from most genjutsu.
Normal visual genjutsu causes blindness by injecting signals into the brain that create the sensation of "seeing nothing."
The brain is the main target.
But Darkness Technique doesn't do that—Li Yao clearly sensed that this jutsu's chakra stays near the eyes, directly severing the neural pathways between the eyes and the brain.
A literal, physical severing.
Right now, the two rogue ninjas still had fully functional eyes—they could see.
But because the signals from their eyes could no longer reach the brain, all their brains could register was darkness. Their perception became total black.
That's the principle of Darkness Technique. Unlike genjutsu that interferes with perception through mental confusion, it's much more brutal and direct, and, surprisingly, much more effective.
When Li Yao compared it to regular genjutsu—which simply scrambled perception—he realized that this kind of straightforward signal-cutting was far harder to dispel.
Thinking of this, Li Yao voluntarily retracted the Black Iron Chains from their bodies.
Once their chakra flow returned, he even disrupted it further to help them try to break free of the jutsu.
"It's useless!"
Even though he'd expected it, Li Yao was still surprised by the sheer power of the Darkness Technique—or rather, by Tobirama Senju's genius.
Truly, this was a man who spent his entire life targeting the Uchiha.
Strictly speaking, Darkness Technique isn't even genjutsu. It only uses genjutsu chakra to activate a form of neural signal severing.
No wonder those under its effect can still use all their senses and ninjutsu—apart from vision.
Now the reason made sense.
Tobirama was ruthless—he gave this non-genjutsu technique a genjutsu-style name.
An unsuspecting enemy would try to remove it like a normal genjutsu and find it completely unremovable. It must be devastating.
Especially for the Uchiha, who were extremely skilled at dispelling genjutsu.
For them, this was a nightmare.
Even the strongest Uchiha couldn't remove it if they didn't know the principle.
To actually break it, one would need to pinpoint the exact position of the Darkness chakra around the eyes, and then precisely inject chakra to disrupt it.
Easier said than done. Very few people could sense genjutsu chakra at that level of precision—especially since the Darkness chakra is so elusive.
That's also why the jutsu continues to be classified as genjutsu, even though it technically isn't.
Still, the technique's mechanism gave Li Yao inspiration.
With a thought, he directed the Darkness Technique's chakra to wrap around the two rogue ninjas' brains.
In his sensory perception, the incoming external signals to the brain traveled through countless neural pathways—so fine and dense that they looked like strands of light, composed of individual photons densely layered across the brain.
To cut these signal paths using Darkness chakra required incredibly precise control.
Luckily, Li Yao possessed exactly that level of control.
With a thought, he severed every signal pathway leading into the brain, using the same technique that disrupted visual input.
In an instant, the two ninja's brains became like isolated orbs—cut off from all sensory feedback from their bodies.
They stopped moving, frozen like vegetative husks.
But then, after just a third of a second, they began thrashing violently again, crying out for mercy.
"What?"
Li Yao frowned.
The Darkness chakra that had encased their brains had just been blown apart by their instinctive chakra bursts.
Genjutsu chakra, to remain undetected, is soft and elusive—like water. One sudden surge of chakra, and it collapses.
That's also why many genjutsu can be broken by disrupting one's own chakra.
Li Yao had discovered a weakness in the Darkness Technique.
Because it wasn't real genjutsu, it forcibly cut off all neural signals to the brain. The targets were paralyzed physically—but their brains remained conscious.
Those two had instinctively used their brain's chakra to forcefully push out the jutsu—and succeeded.
However… the price was steep.
After just a few moments of violent convulsions, both ninja collapsed into drooling, brain-dead vegetables.
Li Yao relaxed and chuckled.
Though they'd broken the jutsu, their brains—so fragile—were damaged by the sudden internal chakra surge.
And this damage wasn't minor.
Now, both were essentially brain-dead due to their own overuse of chakra.
"This technique definitely has value."
Li Yao smirked.
Especially against ninja with poor chakra control, once struck by this new form of Darkness Technique—what he now thought of as a brain-targeted variant—they'd either stay helpless or become brain-dead even if they did manage to dispel it.
Even chakra control experts would need considerable time and precision to dispel it safely.
That window… was more than enough for Li Yao to kill them.
He had just developed a secret technique, a jutsu that could instantly kill at critical moments.
But one question remained:
Why hadn't Tobirama left behind this variation?
Li Yao frowned slightly. The original manga never touched on this side of the Darkness Technique. But that didn't mean it didn't exist. Perhaps someone in Konoha had discovered it?
"Fortunately, I have an edge in chakra sensitivity—and my chakra consciousness naturally rejects any foreign chakra."
"So… I don't need to worry too much."
"Now… what should I name it?"
Li Yao tilted his head. Calling this new, brain-deprivation jutsu "Darkness Technique" felt wrong.
"Since it turns people into vegetables… let's go with: Genjutsu – Sensory Deprivation Technique."
He chuckled darkly. Like Tobirama, he'd just pulled a dirty naming trick—labeling a lethal neural-cutting technique as harmless-sounding genjutsu.
(END CHAPTER)
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