Recovery was a long process, one that could not be sped up.
In this unusual state, Muzan did not trust his useless subordinates. And as for himself, he neither wanted nor dared to appear before others.
So naturally, Rinko, confined to the same room with him, became the only suitable option.
Fate had a cruel sense of humor, even for demons.
The demon Muzan had always considered the least practically useful became, under these special circumstances, the most convenient existence of all.
Rinko wasn't good at fighting. Muzan knew that. But after spending so long learning under Kokushibo, Muzan believed Rinko had at least gained the ability to hunt on his own. Killing a few humans, surely, could not be that difficult for him.
Even if Muzan had never actually seen Rinko kill.
When night fell and Rinko woke, he would stand and leave the house.
The darkness had never felt so long, not when all there was to do was wait.
When Rinko stepped back through the door beneath a moon hanging high at the center of the sky, Muzan saw the basket on his back, a woven carrier that was obviously stolen from someone's home.
And when Rinko returned with a whole basket of people, claiming he'd carried an entire crate of humans back, it would be a lie to say Muzan wasn't startled.
Then Rinko would set the now-empty basket aside and sit quietly against the wall by the doorway.
He didn't eat. He didn't ask questions.
He simply waited for Muzan to devour those people, then stood up and went to do it all again.
Night passed in that loop.
By the final trip before dawn, each time Rinko returned with human corpses on his back, his legs would tremble. It wasn't easy work for him, not at all.
And yet he did it.
Muzan didn't even need to ask to know why.
Because his current body required this much energy to recover. That was all.
When daylight arrived, Rinko would sleep quietly.
The place he preferred was beside Muzan's legs. Sometimes Muzan would eat Rinko's flesh. Sometimes he would feed him blood. But in daylight, Rinko only slept, his awareness of the outside world almost entirely shut down. Whether he had eaten something, or whether something had eaten him, made little difference to him.
When he woke again, everything would look no different than it had in the morning.
Then he would go hunting, and the cycle would begin again.
Rinko didn't like fighting. He didn't like hunting. He didn't like killing.
But Muzan needed to eat humans to recover.
"An injured person needs medicine. A hungry person needs meat. Medicine doesn't always make you better, but meat will always fill your stomach. An injured demon doesn't need medicine. Just meat, and they'll recover. That's wonderful."
Rinko said this with a bright, unhidden smile as he sat by the doorway, looking at Muzan.
During these days, Muzan noticed something he had never paid attention to before, and perhaps could never have noticed before.
Rinko's tolerance was extraordinary. Tamayo had said as much, but Muzan had never truly understood what that conclusion meant. That tolerance made Rinko's recovery equally tenacious. It allowed him to accept more blood, to endure and contain it without his body collapsing.
That was good, of course, but it wasn't enough to interest Muzan.
What was truly interesting was this.
That trait did not apply only to Rinko himself.
His flesh and blood carried the same effect. Devouring Rinko's flesh advanced Muzan's recovery in small increments, progress that would have required countless times more human flesh to achieve.
And when Muzan fed Rinko more of his blood, and Rinko endured it, the effect grew stronger.
A virtuous cycle.
It was rare for Muzan to receive such consistently positive feedback from a demon.
Especially compared to the majority of demons who were either dying, causing trouble, or producing little result no matter what they were made to do, Rinko was like a gift from heaven.
No.
It would be more accurate to say it was something Muzan deserved.
He was the one who chose to keep Rinko. He was the one who turned him into a demon.
This was something he had made with his own hands.
A gift he deserved.
Rinko, still sleeping, knew nothing of the conclusion Muzan had reached, and nothing of what it would mean for him.
He simply sank into his dreams, opening his eyes only when night fell. He rubbed at them and stood, preparing to go out, only for Muzan to stop him.
"That's enough. Let's go."
The basket they had used for so long was tossed aside without care.
The basket, the house, everything here was burned to ash in a single fire.
Above the flames, two figures, one tall and one small, turned and walked away.
For the first time in a long while, Rinko didn't need to run on his own legs.
He was lifted up, allowed to watch the scenery pass, needing only to remember to hold onto that arm.
Muzan took Rinko to many places.
They met many demons, and they also met many humans.
Some became demons.
Some were eaten.
It was a long life of wandering. Rinko experienced something like travel for the first time. By day they would stop and rest. By night they would drift from place to place.
Spring, summer, autumn, winter.
Years passed like that, one after another.
Muzan never stayed anywhere for long. He also never went near places that were too lively, as if he were avoiding something.
Rinko didn't know what, exactly, he was avoiding.
Much later, during one of their rests, Muzan finally mentioned it.
He said they had once encountered someone extremely dangerous. He emphasized the man's red hair and red eyes, the flame-shaped mark on his forehead, and the earrings he wore.
Rinko wasn't good at remembering faces. Those details made him construct a vague image in his mind.
Why did that description sound a little like Kokushibo?
Probably just his imagination.
Honestly, Rinko didn't think he needed to worry anyway.
He couldn't go anywhere by himself. Muzan carried him around everywhere like luggage, like he still hadn't been weaned.
How could he possibly run into that so-called demon-killer?
Rinko thought Muzan's mind was very useful.
Muzan remembered many things, many people. He knew many kinds of knowledge. Sometimes they would settle somewhere remote for a while, and occasionally Muzan would pick up something they hadn't done in years.
Studying.
Reading.
But Rinko's mind wasn't as useful.
Those difficult, rarely-used characters were forgotten clean over the long years, and when that happened, a hand would rap his head in reprimand.
"I'm planning to promote some demons. Let stronger ones receive more of my blood. I'll build a team to deal with those Demon Slayers. What do you think?"
Rinko wasn't interested in how to manage a crowd of demons. He couldn't think of any strategy, either. And considering one of Muzan's teaching principles was this: when adults are talking, children should stay quiet and do their own thing.
So Rinko nodded without a word.
Muzan seemed pleased with the response. That hand moved from scolding to patting his head instead.
At the time, Rinko didn't understand what the Twelve Kizuki were.
But later, he did.
After an unknown number of years, Rinko finally saw Kokushibo again. Kokushibo reported someone's death. Rinko had never heard the name, but Muzan looked delighted.
Rinko thought, then it must be a good thing.
Someone died, and it made Muzan happy. That sounded worth it.
When adults talked, a child was meant to stay to the side by himself.
Even though, by true age, Rinko should have long since been an adult.
His body still looked like a child.
So they continued to treat him like one.
After Kokushibo finished speaking with Muzan, he walked over to Rinko.
Rinko lifted his head.
Those six eyes were as oppressive as ever. Rinko focused on the pair in the middle.
There were characters written within them.
He looked right, then left.
"One. Upper Rank."
Thank goodness.
Characters he recognized. His head escaped disaster.
Rinko exhaled in relief.
"It is Upper Rank One. The Twelve Kizuki are divided into Upper and Lower ranks, six each."
Muzan's voice came from the other side.
Rinko nodded in sudden understanding and made a small sound of acknowledgement.
"Does that mean Lord Kokushibo is the strongest among them?"
Rinko leaned a little closer to Kokushibo and asked softly.
"At present, yes. But other demons can challenge him through a Blood Battle for position. If they succeed, the ranking can change."
Muzan often said Kokushibo had no flaws, except that speaking with him required patience.
Rinko deeply agreed.
Back when he trained under him, once Kokushibo began to "lecture," Rinko could prepare himself to not move all night. Kokushibo had once talked straight through until dawn without pause.
It was, honestly, deeply shocking even for a demon.
"But Lord Muzan told me about the Twelve Kizuki a very long time ago. After so many years, you're still Upper Rank One. Doesn't that mean you're truly incredible?"
Kokushibo didn't answer immediately.
He seemed to think, choosing his words.
And Rinko waited in silence with great patience, waiting for the answer.
Muzan watched the two of them, solemn as wooden dolls, and gave a soft laugh. He let them continue, trading stares in a rhythm so slow they could barely produce two sentences in half a day.
His mood was good for once.
He could indulge them.
When Muzan lifted Rinko onto the eaves, Rinko felt like a kitten Muzan kept.
Carried and picked up all day, taken everywhere, patted on the head for praise, tapped on the head for mistakes.
As for why a kitten instead of a puppy.
Because puppies can't climb onto rooftops.