"Good morning, Lord Kokushibo."
In the brief blackest moment, before the sun fully rose and before the moon completely sank, Rinko toppled straight down in front of Kokushibo.
For a child, one night was an entire lifetime. And playing cat and mouse across an entire mountain was indeed exhausting. But Rinko was a demon, and Kokushibo believed that should make it manageable.
So he only stepped forward, grabbed the back of Rinko's collar with ease, and lifted him as if he were carrying a sack. Then he brought him toward the cave.
To Kokushibo, Rinko was a child whose nature was easy to read. He was simple. Like his appearance, his core was still purely that of a child. When facing someone who seemed older, he would become nervous, stiff, and overly careful. No matter what was said to him, he would do it. Whatever Kokushibo taught, Rinko tried to grasp as quickly as possible. And if he could not learn it, he would keep practicing until he was permitted to stop.
Even though Muzan had said he did not expect Rinko to learn swordsmanship, Kokushibo still tried. Rinko also learned seriously. When it was only practicing forms without striking anything, it looked acceptable. But once he truly attempted to attack, the beautiful long blade in his hands became nothing more than a beautiful pose. It carried none of the force it should have had.
And Rinko could not use Breathing Techniques.
Not a single type.
No matter how Kokushibo taught him, he could not learn.
"My lungs feel like they are going to explode, Lord Kokushibo."
That was one of the rare remarks Rinko made during practice that did not directly relate to the drill itself.
Much later, as Kokushibo watched Rinko fall into deep sleep with the coming of dawn, he realized belatedly that the boy might have been expressing refusal in a tactful way. Perhaps even asking for help.
At the time, Kokushibo did not understand. But he also saw that Rinko truly had no talent for it, so he abandoned the idea of forcing him to continue.
Muzan's judgment, it had to be said, was accurate.
That so-called requirement of "self-preservation" gradually shifted in Kokushibo's mind from a polite instruction into a real bottom line.
A demon who had almost no offensive or defensive ability could not realistically be turned into a combatant.
Rinko was too weak.
As a demon, he was too weak.
Even without comparing him to other demons, if you compared him to boys of the age his appearance suggested, and ignored the special durability of a demon's body, Rinko would still fall into the lowest tier.
If he were not a demon, he most likely would not have survived this long.
Kokushibo often found himself thinking that during training.
It was cruel.And it was real.
But Rinko was not truly useless.
Lately, Kokushibo had been training his reaction speed.
After abandoning offense and defense, this body still retained other traits: sharper sensitivity, greater caution, more careful judgment, and faster movement.
The greatest advantage of training against demons was the high margin for error. Rinko would inevitably be injured in training, but his wounds healed quickly. That meant Kokushibo did not need to hold back. He could simply strike. Training Rinko's regeneration to become even faster was also part of the goal.
And beyond one-sided beatings, Rinko was also forced into the game of cat and mouse.
The "field" was an entire mountain.
Kokushibo would count down, then begin the hunt. Rinko's time to run and hide was only those ten numbers.
At first, Rinko did not display his talent. Kokushibo could easily find the boy every time.
The turning point came after the first night of continuous failure, when Rinko realized how important this truly was.
"How did you find me?"
That was what Rinko asked the seventh time he was caught. At the time, he was hanging upside down by one ankle like a doll, swinging gently in the air.
"You run too slowly. Your movements are too large. Your sound and your shape are both… too obvious."
Perhaps that sentence was the key that opened the door.
Rinko immediately understood that if he only ran, he would always be caught. Competing speed against something that could outrun him easily was impossible.
So he stopped simply running.
He still fled, but he no longer fled blindly. He began to hide. He began to conceal. He began to erase his disadvantages and sharpen his strengths.
A clever little strategy.
And it worked.
From being caught dozens of times in one night, to being caught only a few times, he needed only one month.
Last night, when Kokushibo walked beneath a tree, he had looked up purely on instinct. And only after meeting the boy's eyes did he finally notice Rinko hiding on the branch above him.
Silent.
Motionless.
Even as Kokushibo closed in, entering the range where a normal target would panic and move, Rinko did not. He stayed calm and patient. Aside from a blink when their eyes met, he looked like a part of the forest itself.
That mental fortitude, and the ability to seem nonexistent until the moment he was discovered, was a unique gift.
Kokushibo rarely encountered such a presence. Humans were rare. Demons even rarer.
If Rinko could fight, this talent would be perfect for ambush.
But he could not.
He was simply good at hiding.
He widened the distance first, then used a brief blind spot or a moment of diverted attention to vanish from sight. He used that tiny window to truly "disappear."
Kokushibo had always felt that this did not resemble a strategy meant for fighting demons. It resembled something designed for dealing with Demon Slayers.
A demon could destroy vast areas. A tree could hide in a forest, but if the forest ceased to exist, even a blade of grass would stand out. Humans could not do that. They could not destroy on that scale, nor could they annihilate without restraint.
Rinko remembered Muzan's words.
His enemy was the Demon Slayers.
The ones he needed to avoid were the Demon Slayers.
So the only thing he needed to watch for was the Demon Slayers.
A very simple child.
And setting everything else aside, judging only the results, his training was effective. At least last night, Kokushibo truly caught Rinko only once.
Kokushibo did not completely lose track of him. He could sense the general area. But the closer he got, the harder it became to lock him down.
It was like Rinko was a tiny flame.
From far away, you could see the faint point of light in the dark. But when you raised a torch and walked toward it, the point of light vanished completely. Rinko tucked himself into places even more insignificant, corners even more hidden. Not being discovered was his only goal.
And during training, when there was no person or object to draw attention away and help conceal him, the one searching became the torch.
Rinko treated Kokushibo as the torch.
Once Rinko understood the key, the problem of self-preservation was solved quickly.
But the problem Kokushibo thought would be easier, eating, was not.
Kokushibo did not need to eat much. Partly because of his talent, partly because he had his own standards for food.
Other demons could not be like him, though. So at first he thought: when a demon is hungry, it naturally hunts. At that time, he could train Rinko in the skill of killing. Even if he was not suited for battle, he should at least be capable of catching humans.
Rinko did not get hungry.And he did not eat.
At first, Kokushibo assumed it was another talent.
Later, he realized it was not.
Rather than not being hungry or not eating, it was that the cause of hunger and the target of appetite did not align.
When humans climbed the mountain and lit bonfires at night to cook human food, Rinko would stop, and it was as if even his eyes began to glow. Yet when it came time to actually eat human flesh, he looked indifferent.
Was his head sometimes slow because he was a child?
When Rinko held meat and gnawed at it slowly, Kokushibo could not help suspecting that.
But even if he did not eat, Rinko did not go berserk from hunger, nor did he become weak. And once dawn arrived, he would collapse into sleep immediately, sleeping so deeply that even being lifted and carried around would not wake him.
That was dangerous.
Almost a fatal weakness.
And yet, in practice, it was not.
The first time Rinko collapsed in front of him, Kokushibo watched the boy gradually become a little smaller. Small enough that the oversized outer garment could wrap him completely. And in that moment, the figure right before Kokushibo's eyes vanished from his sensory perception.
As if his senses were being deceived.
His eyes could still see him.His hands could still touch him.
But in Kokushibo's perception, Rinko's presence disappeared.
Rinko was like some special fragile creature.
Because he was so fragile, because too many things in the world would see him as prey, everything he learned while growing up was focused on one thing: making sure no one noticed him, so he could live.
He walked a different path than everyone else.
And he kept walking forward on it without wavering.
Rinko stayed with Kokushibo for a year.
When Muzan came to retrieve him, Rinko had already learned how to hide in the mountain all night without being caught.
As for eating, Kokushibo could only report Rinko's special condition.
And clearly, Kokushibo was not the only one troubled by it.
"Maybe he hit his head too hard."
That was Muzan's final assessment.
Kokushibo expressed agreement with an intensity that surpassed even what Muzan himself expected.