Gold is Thunder. Blue is Water. Cyan is Wind...
As Lucas looked within himself, the five radiant energies shimmered and pulsed, each corresponding to one of the fundamental Breathing Styles.
"Are these truly the five basic Breathing Forms?" Lucas murmured to himself, eyes glowing with wonder.
Then a bold thought surfaced in his mind.
Could it be… if I gather all five Breathing Forms, they'll merge into Sun Breathing?
Sun Breathing—the origin of all techniques. The power that Yoriichi Tsugikuni had wielded to drive Kibutsuji Muzan into terror, nearly erasing him from existence. It wasn't just a technique. It was a legacy. A nightmare that had haunted Muzan for centuries.
If Lucas could master Sun Breathing, even encountering an Upper Moon in the future wouldn't be as terrifying. He might not win, but he'd at least be able to fight back, survive, or even protect others.
Compared to a holding-back Shinazugawa, an Upper Moon fought to kill, mercilessly and with overwhelming force. The difference was like night and day.
But just as quickly as that excitement swelled within him, it faded.
The truth remained cruel and unmoved.
Sun Breathing had long since disappeared from the world. The five basic forms—Thunder, Water, Rock, Wind, and Flame—were merely fragments, incomplete reflections of that ancient power.
Could he really piece it back together from the scattered remnants?
Instead of relying on uncertain fusion, perhaps his best hope lay with Tanjirou. After all, Tanjirou did possess Sun Breathing, passed down in his family. Though he hadn't fully understood or mastered it yet, Lucas could wait—just a bit longer.
He focused his thoughts again on the glowing lights swirling in his inner world.
The five Breathing Forms didn't merge. They circled each other, resonating, but maintaining distinct identities.
However, Lucas noticed something extraordinary.
The five powers had formed a glowing geometric pattern in his mind—a pentagram composed of interwoven energy lines. With each inhale and exhale, the lines lit up subtly.
Each breath felt surreal.
Was this strength truly his own?
Previously, whenever Lucas wanted to use a specific Breathing Form, he had to make slight adjustments to his breathing pattern—just a few seconds' delay—but still, it was necessary.
But now?
He didn't need to switch at all.
With every breath, all five Breathing Forms operated simultaneously.
A shiver ran down his spine.
He felt unprecedentedly strong.
If I entered the Transparent World in this state... even the former Sound Pillar, Oyakata, might not be able to stand against me.
It had only been two months since Lucas began his journey.
The idea that he might already rival such figures made his heart pound. What would Oyakata's expression be if he saw him now?
Suppressing a grin, Lucas returned his attention to the changes in his body and spirit.
The radiant lights of the five Breathing Forms gradually softened, and the sensation of rapid growth began to slow.
His realm wasn't quite at D-rank yet, but Lucas could tell—it was close.
Two days. Maybe less.
Compared to the steady rise in his realm, what fascinated him more was the change in his combat capability.
Before today, he was like a cub with sharp claws that hadn't fully grown.
Now?
He was a young tiger beginning to bare its fangs.
Each Breathing Form added a specific strength to his arsenal:
Thunder Breathing granted unmatched speed and explosive power.
Water Breathing enhanced stamina, flow, and adaptability.
Rock Breathing gave him immense defense and physical durability.
Flame Breathing bolstered his offensive might with burning, sweeping strikes.
Wind Breathing added agility, unpredictability, and subtlety.
With these five forces flowing within him at once, Lucas truly felt reborn.
He didn't even know how powerful he was now. But one thing was certain—he could easily defeat demons like Enmu, even when strengthened by Muzan.
As for facing someone like Upper Moon Three, Akaza… that was still far off. But if Kyojuro Rengoku was by his side, Lucas believed they could turn the tide of battle together.
Maybe he couldn't kill Akaza, but he could save Rengoku. And that alone would be worth everything.
Now, among the current Pillars, only the Insect Pillar, Shinobu Kocho, had yet to accept his friend request.
Lucas considered his timing.
He'd wait until after Shinobu and Tanjirou had their nightly conversation. If her emotions were softened, the chances of success would be much higher.
After steadying the unstable energy from his recent breakthroughs, Lucas felt exhaustion finally descend upon him like a heavy blanket.
Today had been intense—physically, mentally, and emotionally.
He lay down on the futon, eyes fluttering shut, letting his breathing gradually steady.
---
Elsewhere…
Deep within the shifting and ever-dark Infinity Castle—
A place that defied logic, filled with shifting walls and endless corridors, ruled by one being:
Kibutsuji Muzan.
Dressed in a flowing kimono, his face was a mask of quiet fury.
"Kyougai is dead. And now Lower Moon Five is dead as well."
His voice was calm, but the undertone was poisonous.
Kyougai's death didn't matter much—he had long since fallen short of Muzan's expectations and had been cast out from the Twelve Kizuki.
But Rui? Rui had potential. Rui had strength. And now, he too had perished.
Was the Lower Moon division really that useless?
Could any of them actually be relied upon to find the Blue Spider Lily, the key to his long-sought perfection?
And what of that man—Lucas—the pharmacist who had tricked him?
A supposed ally, offering rare ingredients and knowledge.
In truth? A Demon Slayer Corps spy.
How dare he?
Muzan's hands clenched, rage bubbling beneath his perfect, pale skin. He remembered the day he entrusted Lucas with a vital task. He'd believed in his lies, placed hope in him.
Now the memory made his stomach churn.
There was only one thing left to do.
"Summon the Lower Moons."
His voice was quiet, cold, and absolute.
A strum of a biwa echoed through the Infinity Castle.
"Zheng—"
Within moments, five figures were drawn from across the realm and deposited on a massive stone platform.
They appeared without warning—staring around in terror and confusion.
Only Enmu, among them, appeared calm.
The others were visibly shaken.
"Kneel." Muzan's voice was sharper now.
The demons instantly dropped to their knees.
Lucas's betrayal, Rui's failure, and the utter ineffectiveness of the Lower Moons had worn Muzan's patience thin.
One among them, Lower Moon One, tried to speak.
"I am terribly sorry! It was due to your overwhelming aura, my lord, that I—"
"Did I permit you to speak?" Muzan's voice turned lethal.
"Speak only when I ask. Your own will is irrelevant."
He stepped forward.
"Rui is dead. Lower Moon Five. I have only one question."
"Why… are you all so weak?"
Silence.
"Being part of the Twelve Kizuki is not the end goal—it is merely the beginning."
"Devour more humans. Grow stronger. Become something useful."
"In the last hundred years, the Upper Moons have never changed. They are the ones who slay Pillars."
"But you?"
"The Lower Moons are replaced like flies. Time and time again."
His words dripped with disgust, and the pressure in the room grew unbearable. Muzan's bloodlust was suffocating.
Some tried to think a response. Muzan's sharp crimson eyes narrowed.
"What? You have something to say?"
One of the demons, Kamanue, panicked.
"N-No! I—I—please forgive—"
Too late.
A massive fleshy arm covered in eyeballs erupted from Muzan's side and grabbed Kamanue by the waist.
"I'm sorry!! Lord Muzan! Have mercy! Mercy!"
"Bang."
A simple squeeze, and he exploded into gore—his cries silenced instantly.
The rest recoiled in terror.
Another tried to beg, but he was crushed next. One by one, the Lower Moons were wiped from existence as Muzan judged them unworthy.
Only Enmu remained.
Muzan turned his cold gaze toward him.
"And you?"
Enmu stepped forward, a sick, serene smile on his face.
"To be killed by your own hand… and to hear the screams of others as they die… I am already honored."
"Thank you, Lord Muzan, for saving me for last."
There was a pause. Then Muzan nodded.
"I like you."
"I will give you more of my blood."
"Kill the boy with the hanafuda earrings, and I will give you even more."
He stepped closer, eyes narrowing.
"But more importantly…"
"Kill the one wearing the white cloud-patterned haori."
Lucas.
From the memory fragments passed on by Rui before his death, Muzan had seen Lucas.
And he recognized the threat.
"He is far more dangerous than the one with the earrings," Muzan muttered. "Kill him… and I will grant you the blood of an Upper Moon."
Enmu's eyes sparkled with glee.
"Understood."
A final strum of the biwa echoed through the halls—
Zheng—
And the stage was set.
---