"Let me introduce you. Uonuma Usui." Muzan said coldly.
Kokushibo's six eyes shifted slightly, as if he had heard the name before. "Is that the man from the Bakumatsu era, rumored to have killed countless and lost his eyes? One of the Ten Swords?"
"I thought that generation would have long since died out."
"They did die, yet they also came back to life, Kokushibo-dono."
The blind demon let out a light laugh. The laugh carried a desolate quality, like an autumn cicada in late autumn. "This humble one now merely passes the time in the Kyushu countryside, listening to the heartbeats of the dying."
He should have been pierced through the heart by a blade, completely consumed by flames.
But his soul, pure evil for indiscriminately killing the innocent and acting without restraint, ultimately attracted Muzan, who was traveling the regions searching for the Blue Spider Lily.
"A creature, human yet demonic, who lost his eyes but can perceive killing intent through heartbeat? This extreme obsession with survival is truly beautiful."
Muzan granted him a second life, and also granted him cursed power surpassing human limits.
For decades, Usui had lived in seclusion in the mountains and dense forests of Kyushu, feeding on humans who called themselves swordsmen, quietly listening in the darkness as their hearts ceased beating in despair.
"Enough nonsense, Usui." Muzan interrupted impatiently. "I dragged you back from the brink of death not so you could freeload."
"Yes, as you wish, my lord..."
Muzan extended his hand, and Usui obediently knelt before him, heavily planting his short spear on the wooden floor.
Watching Usui drink the plasma he drew out, drop by drop, Muzan's eyes narrowed. "Usui, do you know that as a god, I can hear your thoughts?"
"...." Usui was silent, only greedily absorbing every drop of demon blood.
"I don't know what kind of goods this Shishio in your heart is, but you'd best not compare me to him, fantasizing about any possibility of replacing me."
"We are in a time of need. I only warn you this once. Next time will not be forgiven."
"As you command, my lord...."
Usui humbly withdrew, his thoughts clearly heard by Muzan. 'Shishio-dono.... You see, no matter how this world changes, it ultimately returns to the starting point of survival of the fittest.'
'I will become far stronger than you, and finally devour all the strong....'
Endless greed and ambition, completely unable to recognize the gap in strength between himself and those above him, always fantasizing about the opportunity for a backstab....
'What a disgusting obsession...' But this was also why Muzan chose to save this man.
He always felt that someone like Doma, without joy or sorrow, could not progress.
As a demon, one must have a driving force that constantly pushes oneself forward.
'Like Akaza.... Damn Akaza.'
Thinking of this, Muzan began to lose control. The veins on his brow jumped again. He irritably surveyed the demons before him.
Thus, the new Upper Moons were officially reforged in the bloody feast of the Infinity Castle.
Upper Rank One, Kokushibo.
Upper Rank Two, Hantengu.
Upper Rank Three, Gyokko.
Upper Rank Four, Nakime.
Upper Rank Five, Uonuma Usui.
And Upper Rank Six, Kaigaku.
Muzan looked at this new lineup, composed of remnants from the old era, betrayers from the new, and mutated monsters. The gloom in his heart slightly dissipated.
"As for the remaining ones...."
Muzan looked in every direction of the Infinity Castle, at every dark corner.
Countless lower-level demons, with strange forms and mixed auras, whispered among themselves. They prostrated themselves, lacking even the courage to look up at Muzan.
"Go. According to the set objective… before the final battle, give those damn Demon Slayers some little surprises!"
"I want the night sky completely dyed red!"
Twang—!!!
The biwa sounded again. All the demons vanished in an instant, teleported to different combat areas.
They would serve as the initial cannon fodder in this final battle, to attract the Demon Slayer Corps' attention and sound the bells of destruction.
Meanwhile, in a natural hot spring located in the rear mountains of the Ubuyashiki territory.
After a busy day, the Hashira, unaware of Muzan's plans, were using their rest time to alleviate the fatigue from high-intensity training.
Steam rose, white vapor obscuring vision.
Kyojuro's iconic, flame-like leaping long hair was especially conspicuous on the water's surface.
"Hahaha! Taka! Today's training was truly blood-stirring!"
"Although accelerating the heartbeat to two hundred times is a bit hard on the body, it's passionate! Hahaha!"
He let out a hearty laugh, causing ripples on the water's surface.
Taka leaned against a moss-covered stone at the edge of the hot spring, letting his wet black hair plaster to his forehead, enjoying the rare moment of tranquility with his eyes closed.
"Rengoku-san, please don't talk so loudly while soaking in the hot spring. You'll get oxygen-deprived." Tanjiro kindly reminded him.
He had arrived at the Ubuyashiki estate in the afternoon and joined this training camp.
At that moment, Sanemi, who had been silently soaking on the side, suddenly spoke.
His tone was as impatient as ever, but now his gaze towards Taka held a trace of trust he himself hadn't noticed.
"Hey! Kid! What did you mean today when you talked about tracing the source of Breathing?"
At this, the other Hashira also cast curious glances.
Today, while trying to train to open the Marks, Taka had mentioned this to several other swordsmen, but hadn't gone into detail.
Taka opened his eyes, sweeping his gaze over everyone in the hot spring, and spoke directly: "I'll make it short. I plan to restore Sun Breathing."
"Sun Breathing?"
Most Hashira were hearing this term for the first time. Only Kyojuro had previously seen related records with Taka in the Flame Hashira's Book.
"I believe each of the five main Breathing Styles contains at least one characteristic of the original breathing. So I intend to reverse engineer it and recreate the original breathing."
"This is too reckless!" Sanemi's eyes were full of doubt. "Breathing Styles were developed by countless predecessors over centuries. You want to reverse engineer it based on one person's feeling?"
"Not just me alone. All of us together." Taka's tone was firm. "If following the rules could kill Muzan, he would have died centuries ago. Just because predecessors couldn't learn a breathing style doesn't mean we can't."
"Amida Butsu...." Gyomei was still fingering his prayer beads even in the hot spring. "I understand Taka's idea. If this truly is the necessary path to save all living beings, this humble priest is willing to fully cooperate."
"Also, Tanjiro."
Taka pointed to the bewildered Kamado boy. "According to a reliable information source, your Kagura earrings repeatedly flash back in Muzan's memories. I believe your Hinokami Kagura is also key to restoring Sun Breathing. I want you to join the Hashira-level training as well."
"Me?? But...."
Tanjiro was about to say he wasn't a Hashira-level swordsman and might hold them back, but Taka ignored him.
He looked at Zenitsu, who had been quietly dozing by the hot spring's edge, and calmly said: "Additionally, in light of Agatsuma Zenitsu only knowing the First Form.... I've decided to go to Mount Momo and consult the former Rumble Hashira, Kuwajima Jigoro, regarding the sword forms of Thunder Breathing."
"—!! You're going to see Gramps?!"
This time, Zenitsu couldn't pretend to be asleep. He gasped in nervous surprise.