Kokushibo, this strongest Upper Moon standing at the pinnacle of the Twelve Demon Moons, had already turned to ash under the blade of Yoriichi Tsugikuni's heroic spirit.
Thus, the final chasm blocking the path between the Demon Slayer Corps and their ultimate goal had been completely cleared.
All that remained was the source of all evil hidden in the deepest part of the Infinity Castle, who had claimed the lives of countless swordsmen for a thousand years—Muzan Kibutsuji.
On the road leading to the core of the Infinity Castle, the remaining Lower Moon demons and weaker aberrant demons.
Swarmed like hyenas smelling blood, trying to use their insignificant power to block everyone's advance.
They roared and howled, their twisted limbs wielding claws and venomous stingers, forming a nauseating line of defense.
However, facing this rabble, Phaethon at the front didn't even lift an eyelid.
He simply casually waved his hand, as if shooing away annoying insects.
Instantly, blazing golden light gathered and compressed in his palm.
Then transformed into a terrifying torrent of energy capable of burning the heavens and boiling the seas—
This was exactly what he remembered, an application of Asura's Fluctuation Power, the Explosive Flame Fluctuation Sword!
Boom——!!!
Golden flame waves like volcanic lava bursting from a dam swept forward with overwhelming force!
All Lower Moon demons and aberrant evil spirits along the way, the moment they contacted this pure light and fire fluctuation energy, couldn't even let out screams.
They were completely vaporized like snow thrown into a furnace, not leaving even a trace of ash!
The power of the Explosive Flame Fluctuation Sword didn't diminish at all, like a divine punishment sword that split heaven and earth, charging forward relentlessly to bombard the seemingly indestructible walls of the Infinity Castle!
Rumble——!!!
Deafening roars accompanied by violent spatial tremors came forth, and the walls of the Infinity Castle were like paper.
Easily torn and shattered by the Explosive Flame Fluctuation Sword!
Layer after layer, whether physical obstacles or the bizarre structures of spatial dimensions, all turned to dust before this absolute power!
This single Explosive Flame Fluctuation Sword not only cleared away all the small fry blocking the way.
It also directly penetrated the layers upon layers of spatial barriers in the Infinity Castle, forcibly carving out a path straight to the core area!
At the end of the path, in the depths of that forcibly broken space, a figure was cowering there in utter terror.
He had slightly curly black hair, plum-red eyes, a handsome face with a sickly paleness.
This was none other than the one the Demon Slayer Corps had pursued for a thousand years, the instigator of all tragedies—Muzan Kibutsuji!
That explosive flame fluctuation just now, like a falling sun, its terrifying power had completely shattered the last trace of pride and dignity in Muzan's heart as the Demon King!
His entire body trembled violently like a sieve, those plum-red eyes filled with endless fear and horror!
This power... this punishment-like power!
Instantly reminded him of that man who had dominated him like a nightmare hundreds of years ago—Yoriichi Tsugikuni!
No! That's not right!
Muzan's heart screamed madly, this power was ten thousand times more terrifying than Yoriichi's pure Sun Breathing!
This was a more fundamental, more vast force that seemed capable of easily annihilating all things in the world!
If that explosive flame fluctuation hadn't deliberately veered slightly away, he had no doubt.
He probably wouldn't have even a single cell left, having completely disappeared from this world long ago!
He could even feel that just standing at the edge of that power's residual fluctuations, his demon cells were instinctively trembling and dissolving!
The reason Phaethon didn't directly obliterate Muzan with one strike was simple—
As he had thought before, Muzan as the final boss should become experience points for his Familia's growth, not be easily harvested by him as a deity.
Especially Kanae, slaying the Demon King was her and the entire Demon Slayer Corps' thousand-year wish.
This glorious moment must be completed by her own hands.
"Muzan Kibutsuji!!!"
Just as Muzan was scared witless by Phaethon's power, almost losing his ability to think, a voice full of bone-deep hatred rang out behind him.
Muzan turned his head with difficulty, seeing the approaching members of the Demon Slayer Corps, led by—Kagaya Ubuyashiki!
The moment he saw this face, the fear in Muzan's heart was temporarily replaced by boundless hatred!
The Ubuyashiki family!
Again, you damned Demon Slayer Corps!
If not for this family that had clung to him like a parasitic worm for a thousand years, why would he have had to hide and skulk like a rat for over a millennium?
He should have found the blue spider lily long ago, overcome sunlight, and become a truly perfect being!
Originally, Muzan had been searching for their location himself, never expecting they would come to him!
"Unforgivable! I'll turn you all... turn you all into minced meat!"
The brutality in Muzan's heart was completely triggered, and he instinctively wanted to use his most cruel methods to tear Kagaya into pieces!
But just as his gaze was about to lock onto Kagaya.
He saw the person standing beside Kagaya—Phaethon.
Merely seeing Phaethon's figure, the rage and killing intent that had just ignited in Muzan's heart was like having a basin of ice water poured over his head, instantly extinguished completely!
Without even needing Phaethon to make any movement, just the warm and sacred light like the sun.
That emanated from within him every moment.
Already made Muzan's demon cells feel excruciating pain as if being burned by fierce flames!
As if they would be completely purified in the next second!
Escape!
Must escape!
At this moment, Muzan no longer had any thought of killing Kagaya.
His only thought was to immediately flee from this place!
Flee from this being emanating terrifying light!
However, just as he was about to forcibly tear through space and exit this alternate dimension of the Infinity Castle—
A pink figure moving at extreme speed appeared before him like a teleportation!
It was Butterfly Kanae!
Her eyes were cold, filled with the resolve to cut through everything!
The Nichirin blade in her hand, after changing jobs to Sword Wielder and gaining a LV2 level increase, had become even sharper and deadlier!
"Splash!"
The blade flashed!
So fast that even afterimages were hard to catch!
This strike from Kanae went straight for Muzan's neck!
If it hit, it would be enough to instantly sever his head!
But Muzan was after all the Demon King who had lived for a thousand years, his battle instincts had long been ingrained in his bones.
At the critical moment, he forcibly twisted his body at an unimaginable angle, narrowly avoiding this fatal strike!
However, the hat on his head wasn't so lucky, instantly cut by the sharp blade and falling to the ground.
Muzan broke out in a cold sweat, looking at Kanae before him in disbelief.
This little girl from the Demon Slayer Corps now displayed speed and power that had reached such a terrifying level?
Just as Muzan was shocked, Phaethon finally made his move.
He didn't attack directly, just casually raised his hand and gently pointed at the space where Muzan was located.
"Light Prison."
Hum——!
Invisible golden light instantly condensed, forming a solid cage made of pure light energy, firmly trapping Muzan in place!
The light prison barriers emanated a sacred and warm aura, yet made Muzan feel as if he were in a furnace!
He could feel that if he tried to break through by force.
The demon cells that made up his body would be instantly dissolved!
"Damn it!"
Without a doubt, Muzan was completely trapped!
This light prison was exactly the stage Phaethon had carefully crafted for Kanae, an arena specifically for slaying the original Demon King!
Seeing that escape was hopeless, and that mysterious terrifying man had no intention of personally entering the battle for now.
Muzan turned his gaze back to Kanae before him, those plum-red eyes flickering with cruel and mad light.
"Very good... very good!"
Muzan let out a low laugh, carrying a hint of hysterical madness.
"Even if you want my life, I'll drag you to hell with me!"