Each Nen Ability type has varying degrees of application and nature transformation.
Manipulation-type abilities have three relatively clear level classifications: Request-type, Semi-forced-type, and Forced-type.
Request-type is the lowest level in Manipulation-type, giving the target some room for choice while making them act for the ability user. The advantage of this type of control is that it can manipulate more people with less Nen.
Simply put, it's related to 'suggestion', just slightly stronger than 'suggestion'.
Semi-forced-type involves seizing the target's body for free manipulation, or forcing the target into a situation where they have to act according to commands.
Forced-type involves directly seizing the target's body and mind for free manipulation.
Like Shalnark's [Black Voice], it's a Forced-type Manipulation ability. Besides that, Illumi's Needle People also belong to the application of Forced-type manipulation.
Compared to Request-type and Semi-forced-type, the moment a Forced-type Nen effect is applied to a target, it's equivalent to destroying the target's body and mind. Even if the Nen is withdrawn, the target becomes a walking corpse.
The categories described above are only Manipulation-type applications targeting living beings. There are also applications for manipulating inanimate objects, Nen Beasts, and even the most fundamental Nen itself.
Thus, each Nen Ability type can derive extensive applications. Even what seems the most crude and direct, the Enhancer-type, actually has broad application methods.
The needle Illumi inserted into Killua's head was Semi-forced-type Manipulation Ability, belonging to the type that forces the target into a situation where they must act according to commands.
And the command he implanted in Killua's head was: When encountering an enemy stronger than yourself, run quickly.
This command was absolute. Even if running required abandoning family or friends, as long as the conditions fit, the command would force Killua to act.
Because of this, as long as Illumi's Nen continued to control Killua, Killua could never truly know his own upper limit of strength.
Especially when facing enemies like Chimera Ants with exaggerated Manifested Aura, often upon realizing the gap, he would lose the will to fight, naturally unable to fight with full strength.
And at this moment, Killua pulled out the needle himself.
'Semi-forced-type isn't suitable. Then I'll directly use Forced-type Nen.'
Illumi's eyes seemed to generate cold vortices.
After concluding that the coercive control of Semi-forced-type was no longer suitable for Killua, the countermeasure he thought of wasn't another type of Semi-forced-type, like seizing body freedom for manipulation. Instead, he directly jumped to Forced-type.
Directly seizing body and mind, turning Killua into a puppet for free manipulation.
The reason for this thought was because Illumi was angry.
He wasn't angry that Killua could pull out the needle himself, but that after pulling out the needle, Killua completely ignored him. This gave him an unpleasant experience akin to loss of control.
The term 'loss of control' isn't friendly for Manipulation-type Nen Users with strong desires for control.
Killua indeed ignored Illumi's existence, or rather, no longer regarded Illumi.
Because, along with pulling out that needle, the fear accumulated over a long time because of Illumi also vanished like smoke.
Killua's hair, clothes, even his entire body had become electrified.
After crushing Harrison's flesh, Killua didn't attack again proactively. Instead, he stood in front of Gon like a mother hen protecting her chicks.
Gon was stunned by the power Killua suddenly erupted with, just dumbly watching Killua's back.
"I don't like changing my mind on the spot."
Harrison glanced down at the large missing chunk of flesh on the right side of his abdomen, blood continuously flowing, then stared at the electrified Killua.
Even though Killua changed from a house cat to a fierce tiger, Harrison still felt it necessary to deal with the weak first. And Killua clearly intended to protect Gon, which would restrain Killua.
"Take one more step, and I'll kill you."
Killua coldly stared at Harrison, repeating what he had just said.
Harrison's pupils contracted, then relaxed. His tall, thin yet muscular body suddenly erupted with a powerful Aura.
Whoosh!
Harrison's body disappeared from its spot.
Simultaneously, Killua raised his hands like lightning, adopting a starting posture similar to Zeno's Dragon Head technique. His left and right hands positioned one above the other, five fingers transformed into hooks.
The moment he adopted the starting posture, Killua's body also disappeared, leaving only a small cluster of electricity where he stood.
Both sides' speed was so fast they only left afterimages, crossing each other in a space difficult for the naked eye to capture.
The next second, Harrison's body materialized, but his head was missing, and a large amount of blood seeped from the heart area on his chest.
On the other side, Killua held Harrison's head in one hand and his heart in the other.
That starting posture similar to Dragon Head technique involved one hand attacking the heart, the other attacking the head.
But in that brief clash comparable to the speed of light, Killua incorporated the Rhythm Echo into his attack, using variations in speed to confuse Harrison's defense.
One must know, the faster the speed, the harder it is to execute speed variation techniques. And when speed rivals lightning, the difficulty is even more indescribable, yet Killua did it.
Because of this, the effect completely confused Harrison. When Harrison set up defense on his head, Killua took the heart first. When Harrison, realizing too late, set up defense on his chest, Killua took the head later.
This one-after-the-other attack, completely shaking off Harrison, simultaneously targeted Harrison's two vital points… a complete certain kill.
After the outcome, Harrison's face was full of bewildered incomprehension.
Ending so quickly left him extremely puzzled, even feeling as if in a dream.
No matter what, it shouldn't have been this result.
Then, without a word, Killua crushed Harrison's head and heart, decisively ending Harrison's life.
Simultaneously, Harrison's headless body, having come to a stop, fell to the ground with a thud, losing all signs of life.
After dealing with Harrison, Killua finally looked directly at Illumi.
No anger, no pride, just a calm expression.
Facing Killua's gaze, Illumi walked forward expressionlessly, simultaneously emitting a malicious aura.
In the past, this Aura would have rendered Killua immobile, but now, Killua remained completely unaffected.
"I'm pleased."
Illumi said while walking, already holding several bead-headed pins in his hand.
Killua slowly raised a hand, extending his index finger to press against the front of his forehead, coolly stating, "Don't even think about sticking needles in my head again. If you show even the slightest intention, I'll kill you."
"Hmm, kill me?" Illumi pressed his lips into a smile. "With your ability?"
Before the words finished, the Killua in Illumi's eyes suddenly disappeared.
Illumi's eyes narrowed, his pin-holding hand stabbing backward, but stopped instantly.
Killua's sharpened nails were pressed against the back of Illumi's neck.
Illumi's reaction was fast enough, but still a step slower than Killua.
Because Killua had actually held back during the previous fight, not displaying his fastest speed.
The motive for doing this was to mislead him, then deal with him.
A move of considerable confidence.
After pulling out the needle, Killua underwent a metamorphosis.
"You can try," Killua said coldly.
That tone left no room for doubt… he would indeed do as he said.
Though a vital point was threatened by Killua, Illumi showed no fear, suddenly letting out a low laugh.
Hearing Illumi's laughter, Killua remained unmoved.
"You've grown up."
Illumi said in a tone that was hard to decipher.