Work Text:
Killua thinks it is very unfair that he must be the one to help Illumi practice his Nen. Killua doesn’t know how to use Nen on his own, and for as much of a prodigy as he may be, he’s nowhere near strong enough to fight his big brother. Illumi would probably learn better from Silva or Zeno, who are both experts at their own Nen.
But Killua doesn’t say any of that. He doesn’t protest at all, following Illumi to the wide, empty room they use for different types of training. They both know Killua doesn’t need to be strapped down for something like this, because he won’t fight or resist, but Illumi does it anyway. Thick leather holds Killua to one of the tables, the one his mother likes to use when taking tests.
“This won’t hurt a bit,” Illumi says. His voice is very soft, seductive, almost. The perfect voice to soothe or persuade, if Killua were anyone else. He isn’t, though, and he will always be able to hear the menacing, chilling undertones. Illumi’s voice will always scare him.
Illumi aims a needle at Killua’s forehead, right in the center, and pushes.
Killua knew Illumi had lied. He’s not sure anything he’s ever been put through hurt worse than this. It’s blindingly excruciating, making his vision flash frighteningly white. He thinks for a moment that he is going to pass out, and he cries out as the pain in his head only continues to grow. It feels like his brain is being torn in two.
“Stop that,” Illumi commands. “Calm down.” Killua’s mind goes silent. Completely empty. The pain is gone as Illumi’s hands recede from the corners of his vision. Killua breathes evenly, deeply, utterly content in everything but soul. There are no panicked thoughts, because there are no thoughts. “Interesting.” He writes something down. “Stand up.” Killua’s wrists jerk at their bindings. He can’t break leather, at least not yet, but order repeats in his mind like an imperative, something he has no choice but to obey. “Stop.”
Illumi peers down at him, looking absolutely fascinated, which is weird because usually Illumi has two expressions; neutral and angry.
“Stay still.” He begins to pull out the needle. For a while, even through the pain, Illumi’s orders of ‘calm down’ and ‘stay still’ keep him docile, but eventually, whatever effects the needle had wear off, and Killua whimpers. His mother is working on training those sounds out of him, but she hasn’t managed it just yet. The leather straps release, and without another glance, Illumi is gone.
Killua is not strapped down, this time, probably because his father wouldn’t like it if he was. He has very different views than his mother. Silva and Illumi both stand over where he lies, his father looking mildly interested, but mostly bored, like usual.
“Don’t thrash,” Illumi says, lining up his needle. Killua bites his tongue so as not to shout, but he thinks he probably whines a little, but overall he thinks he is successful. “Stand up.” Just like before, his mind becomes one-track, with no room for anything else. He stands, feeling very much like a blank canvas on which his brother is going to paint with commands.
“Very interesting,” Silva murmurs. “Killua, walk to the wall.” Killua doesn’t move. “It only works for you, then. That makes sense.” They stare at Killua, but he doesn’t have the presence of mind to be bothered by it. He doesn’t know what they’re looking for in him, either.
“I don’t know yet if the effect wears off after some time, or if there is a limit to what can be asked.” Illumi says. “I also am not sure if one would build a tolerance and be able to free themself from my control.” Silva looks at Killua, thoughtfully.
“If anyone would, it would be Killua.” Illumi nods. “You should use him to continue your testing. Kalluto may be of use as well, as he is much more ordinary.”
“Yes,” Illumi agrees.
“Remove the needle, for today,” Silva tells him. “You may continue your testing tomorrow. But Illumi, do not hurt Killua.” He doesn’t really need to say it, Illumi knows the rules, but the dangerous glint in Silva’s eyes says something a little more. Illumi must be very careful with Killua. He cannot be damaged.
“Yes.”
Illumi leaves the needle in for hours the next day, pushing Killua’s body right up to its limit. He loosens his hold, allowing Killua to think but not resist. He does this so Killua can answer questions and gather data.
“What does it feel like when it is inserted?” “What does the command do to your mind?” “Does it cause any side effects? If so, what are they?” “Do the commands compel you to surpass your physical or mental limitations?”
He answers them as best he can. Illumi hooks him up to a heart monitor and asks him to increase his heart rate, which does nothing. Normal bodily function cannot be halted or altered by his orders. When he asks him to stop breathing, though, Killua obeys until black dances in his vision and Illumi accepts that he won’t be stopping until he’s unconscious.
Silva comes back to check on them after a few hours, looking at Illumi’s notes with more intrigue than Killua has seen on him in years.
“I think it would work,” Illumi says. Killua frowns. What is ‘it’? Silva hums. “It wouldn’t hurt to try. I could always release him should there be any adverse effects.”
“I suppose,” Silva murmurs. “Yes, I think you should try it. If anything happens while you’re away, though, you will be punished.” Illumi nods. He never disagrees with Silva.
“What are you going to do?” Killua ventures, making his voice as big and bold as he can. ‘You do not show fear, ever.’ echoes through his mind.
“Don’t be frightened, Kill’,” Illumi soothes anyway, in that silken voice of his, because he can always sense Killua’s fear. “You won’t remember it anyway.” And Killua knows no more.