"Let me introduce him—Uonuma Usui," Muzan said coldly.
Kokushibo's six eyes shifted slightly, as if he had heard the name before. "Is he the Ten Swordsman from the Bakumatsu era who was rumored to have killed countless people and lost both of his eyes?"
"I thought people from that generation should have long since died out."
"I did die, yet I also lived again, Lord Kokushibo."
The blind demon let out a faint chuckle. The sound carried a bleakness like the last cicadas of late autumn. "These days I am merely a blind demon hiding in the countryside of Kyushu, passing the time by listening to the heartbeats of those on the verge of death."
He should have died—his heart pierced by a blade and his body consumed by flames.
But his purely evil soul, one that slaughtered innocents without restraint, eventually attracted the attention of Kibutsuji Muzan, who was traveling the land in search of the Blue Spider Lily.
"A human monster who lost his eyes yet senses killing intent through heartbeats? Such extreme survival obsession… how wonderful."
Muzan granted him a second life, along with cursed power that surpassed the limits of humanity.
For decades, Uonuma Usui hid within the mountains and forests of Kyushu. He fed on humans who proudly called themselves swordsmen, quietly listening in the darkness as their hearts stopped beating in despair.
"Enough nonsense, Uonuma," Muzan interrupted impatiently. "I didn't drag you back from the brink of death so you could freeload."
"Yes, everything will be as you wish, my lord…"
Muzan extended his hand. Uonuma obediently knelt before him and planted his short spear heavily against the wooden floor.
As Uonuma slowly drank the blood Muzan tore from his own body, Muzan narrowed his eyes.
"Uonuma. Do you realize that as a god, I can hear your thoughts?"
"…"
Uonuma said nothing, greedily absorbing every drop of demon blood.
"I don't know who this Shishio in your mind is, but you'd better not compare me to him or imagine that you could replace me."
"Now is a time when I need people. I will only remind you once. There will not be a second warning."
"Understood, my lord…"
Uonuma Usui withdrew respectfully, yet his thoughts were perfectly clear to Muzan.
'Lord Shishio… you see? No matter how the world changes, it always returns to the law of the jungle.'
'I will become far stronger than you ever were… and in the end I will devour every strong person.'
Endless greed and ambition. A creature incapable of recognizing the gap between himself and those above him, always dreaming of betrayal.
What a nauseating obsession.
But that was precisely why Muzan chose to save him.
He had always believed that someone like Doma, who felt neither joy nor sorrow, could never truly improve.
A demon needed motivation—something that constantly drove them forward.
Just like Akaza.
That damned Akaza.
The thought made Muzan lose his composure. The veins on his forehead throbbed again as he irritably surveyed the demons before him.
At this moment, the brand-new Upper Six had been officially reconstructed in the bloody banquet of the Infinity Castle.
Upper One — Kokushibo.
Upper Two — Hantengu.
Upper Three — Gyokko.
Upper Four — Nakime.
Upper Five — Uonuma Usui.
And Upper Six — Kaigaku.
Muzan looked at this new lineup composed of remnants of the old era, traitors of the new era, and grotesque mutations. The gloom in his heart lightened slightly.
"As for the rest of you…"
Muzan gazed toward every dark corner of the Infinity Castle.
Countless low-ranking demons with strange forms and mixed auras whispered among themselves. They knelt on the ground, not even daring to raise their heads to look at Muzan.
"Go. Follow the predetermined objectives."
"Before the final battle begins, give those damned demon slayers a little surprise."
"I want the night sky… to be completely dyed red."
Zheng—!!!
The sound of the biwa rang out once again.
All the demons instantly vanished from where they stood, teleported to different battlefields.
They would serve as the first wave of cannon fodder in the coming war, drawing the attention of the Demon Slayer Corps and sounding the bell of destruction.
At the same time, in a natural hot spring on the back mountain of the Ubuyashiki estate.
After an entire day of exhausting training, the Hashira—completely unaware of Muzan's plans—were using this rare moment of rest to relieve the fatigue of their intense exercises.
Steam filled the air.
White mist obscured their vision.
Rengoku Kyojuro's iconic flame-like hair floated on the surface of the water, impossible to miss.
"Hahaha! Asuka! Today's training really made my blood boil!"
"Even though accelerating the heartbeat two hundred times was a bit hard on the body, it was incredibly exhilarating! Hahaha!"
His hearty laughter sent ripples across the hot spring.
Asuka leaned against a smooth stone at the edge of the spring, his short black hair damp and clinging to his forehead. With his eyes closed, he quietly enjoyed the rare moment of peace.
"Mr. Kyojuro, you shouldn't speak so loudly while soaking in a hot spring. You might run out of oxygen," Tanjiro kindly reminded him.
He had arrived at the Ubuyashiki residence in the afternoon and joined the training session.
At that moment, Sanemi Shinazugawa—who had been silent until now—suddenly spoke.
His tone remained as impatient as ever, but when he looked at Asuka now, there was a trace of trust even he hadn't realized.
"Hey, kid. What did you mean earlier about that so-called tracing-back breathing?"
The moment he said that, the other Hashira turned their curious gazes toward Asuka as well.
Earlier that day, while attempting to train toward awakening the mark, Asuka had briefly mentioned the idea to several swordsmen but hadn't explained it in detail.
Asuka opened his eyes and looked around at everyone in the hot spring before speaking directly.
"I'll keep it simple. I plan to restore the Sun Breathing."
"The Sun Breathing?"
Most of the Hashira were hearing this term for the first time. Only Rengoku Kyojuro had seen records of it earlier together with Asuka in the Flame Hashira's book.
"I believe the existing five fundamental breathing styles each contain at least one characteristic of the original breathing. So I plan to reverse-engineer them and recreate the original."
"That's ridiculous!" Sanemi's eyes were filled with doubt. "Breathing techniques are the result of centuries of experience passed down by countless predecessors. And you want to reverse them based on one person's intuition?"
"Not one person. All of us together," Asuka replied firmly. "If following the rules could kill Muzan, he would've been dead centuries ago. Just because the previous generation couldn't learn a breathing style doesn't mean we can't."
"Amitabha…"
Gyomei Himejima continued turning his prayer beads even while soaking in the hot spring.
"I understand Asuka's idea. If this truly is the path required to save all living beings, this monk will give it his full support."
"There's also something else, Tanjiro."
Asuka pointed at the confused Kamado boy.
"According to a… reliable source of information, your Hanafuda earrings repeatedly appear in Muzan's memories. I believe your Hinokami Kagura is also a key to restoring the Sun Breathing. I want you to join the Hashira-level training."
"Me? But…"
Tanjiro was about to say that he wasn't a Hashira-level swordsman and might hold everyone back, but Asuka ignored the protest.
He turned his gaze toward Zenitsu, who had been quietly dozing at the edge of the hot spring, and spoke calmly.
"Also, considering that Zenitsu Agatsuma can only use the First Form… I've decided to make a trip to Mount Momoyama to ask the former Thunder Hashira, Jigoro Kuwajima, about the sword forms of the Thunder Breathing."
"—! You're going to see Grandpa?!"
Zenitsu could no longer pretend to sleep and shouted in shock.