Muzan's gaze involuntarily turned toward the steel giant.
He watched as Optimus Prime slowly raised his arm. After a dazzling flurry of mechanical transformations, an energy cannon brimming with sci-fi aesthetics took shape.
Accompanied by the hum of surging energy, a massive blue beam of light blasted forward.
Wherever the beam passed, a massive horde of fearless newborn demons, along with the twisted architecture beneath their feet, were completely vaporized, leaving not a single speck of ash behind.
Hashirama Senju looked at the chaotic battlefield before him, then glanced at the Demon King being toyed with by the purple-haired man in the distance, and couldn't help but scratch his head.
He turned and spoke to Naruto Uzumaki beside him.
"Naruto, I feel like this guy attacking us isn't... all that strong?"
"Could he be hiding some powerful trump card he hasn't used yet?"
Naruto, completely unbothered by such thoughts, responded with sheer excitement.
"Who cares, First Hokage! Let's just finish him off quickly and go get ramen with Sasuke!"
The Demon Slayer Corps and these otherworldly visitors commenced a one-sided massacre of the demon army with an almost playful demeanor.
The Love Hashira, Mitsuri Kanroji, merely flicked her whip-like sword, and a majestic blade of air cleaved a massive building in half.
Wherever the Stone Hashira, Gyomei Himejima, swung his iron fists, both demons and structures were reduced to dust.
A demon hiding in the shadows fired a final artillery shell at Gyomei, landing a precise hit right on top of his head.
However, the shell shattered instantly upon impact, like an egg striking a rock.
Gyomei's smooth, shiny bald head remained completely unscathed.
Watching this battlefield where the art style had completely collapsed, Muzan Kibutsuji's self-proclaimed godhood wavered violently for the first time.
'These guys...'
'Just what the hell are these guys?!'
This was completely, utterly different from the weak, pathetic Demon Slayer Corps in his memories!
He had finally become the Ultimate Being—was he really going to die here?
No! He couldn't accept this! He was the Ultimate Being!
"Roar—!!!"
His endless humiliation and fury finally erupted into a deafening roar.
Muzan's handsome face twisted completely as his body began to rapidly expand. Bulging muscles tore through his luxurious suit, and in the blink of an eye, he transformed into a towering giant of flesh and blood over ten meters tall.
He spread his arms wide, every cell in his body greedily absorbing the sunlight streaming in from the dome.
He intended to use this supreme power of the sun to utterly crush the purple-haired man who dared to mock him.
However, facing this berserk power, Kars simply spread his arms with elegance, equally enjoying the warm sunbath.
His method of absorbing sunlight was far more efficient and graceful than Muzan's crude devouring.
The light gathered in his pale palm, condensing into a miniature sphere of pure solar energy.
The energy contained within that sphere was the perfect manifestation of Hamon Overdrive cultivated to its absolute peak.
"Die!"
Putting everything on the line, Muzan's massive body instantly disintegrated into billions of microscopic spikes carrying his cells. Like a torrential storm of blood, they shot toward Kars, blotting out the sky.
Countless spikes successfully pierced into Kars's body.
Yet, in the very next second, a change occurred within Kars's body that Muzan couldn't even begin to comprehend.
The moment those cells carrying his will and power entered Kars, they were instantly assimilated and broken down by a higher tier of cellular structure.
Not only did they fail to cause any harm, but they also became nutrients to nourish his opponent.
A smile of sheer enjoyment even surfaced on Kars's face.
"Thanks for the meal."
"Your cellular structure is quite fascinating and holds immense potential, but the way you utilize it is far too crude!"
On the other side of the battlefield, Tanjiro Kamado gripped his Nichirin Sword, which blazed with golden flames. Facing the swarming horde of demons, his eyes were clear and resolute.
Sun Breathing: Dance!
With a single swing, the blade carried the majesty and compassion of a blazing sun.
The moment the weaker demons touched the edge of the blade, their faces showed no trace of pain. Instead, they wore expressions of peaceful liberation as their bodies dissolved into motes of light and vanished into the air.
This was the "Compassion of the Sun."
As for the powerful Demon Generals, they were instantly incinerated by the terrifying, berserk power erupting from the blade like a solar flare, leaving absolutely nothing behind.
This was the "Pride of the Sun."
"Beast Breathing, Secret Art: Thunder Bagua!"
Inosuke Hashibira fully unleashed the power of his Devil Fruit, transforming into a mythical beast tens of meters tall with a blue face and sharp fangs, wielding a massive kanabo.
He let out a roar that shook the entire Infinity Castle and rampaged through the demon horde.
Every swing he made carried the overwhelmingly tyrannical Conqueror's Haki.
The high-speed regeneration the demons prided themselves on became utterly meaningless in the face of his mountain-shattering strength.
Back in front of the throne, Kars had completely lost his patience for toying with his prey.
His arms shifted and transformed, surprisingly turning into bone whips similar to Muzan's.
However, his bone whips radiated a sun-like brilliance, proving to be far tougher, faster, and deadlier than Muzan's.
Amidst the flashing light, Muzan's remaining body was continuously sliced and dismantled.
His vaunted regeneration speed couldn't even begin to keep up with the rate of destruction.
As he carved Muzan into countless pieces, Kars spoke coldly.
"You can't even perfectly control your own genes."
"You can't even create new life, only capable of imitating and regenerating in such a clumsy manner."
"And you think you're worthy of calling yourself the 'Ultimate Being'?"
On the other end of the battlefield, the doom of the Upper Rank demons had also arrived.
The strongest techniques and variations of Kokushibo's Moon Breathing were effortlessly seen through by Sasuke Uchiha's Mangekyo Sharingan.
Ultimately, he was casually bisected by Sasuke's blade, then burned into nothingness by Amaterasu.
Right before his death, reflected in his six eyes was the figure of his younger brother—as dazzling as the sun, the man he had spent his entire life trying to catch up to.
As for Doma, Josuke Higashikata used the power of Crazy Diamond Requiem to "restore" him together with the specialized, gene-rewriting lethal poison created by Shinobu Kocho.
His body perfectly fused with the deadly poison, and amidst a brilliant flurry of ice crystals, he completely dissolved into nothingness, still wearing that equally hollow, fake smile on his face.
Meanwhile, in his battle against Muichiro Tokito, Akaza was ultimately crushed head-on by his own technique, Destructive Death: Annihilation Type, which Muichiro had instantly learned and optimized using the Migeika Eyes.
In the final moment before his body faded away, he saw it.
He saw the absolute pinnacle of martial arts that he had spent his entire life pursuing.
He smiled in peaceful relief.
Utterly overwhelmed by Kars, his dignity and confidence trampled to dust, Muzan Kibutsuji finally descended into ultimate madness.
Looking at the incomprehensible monsters surrounding him and sensing his own irreversible defeat, he let out a soul-piercing, agonizing shriek.
"If I cannot become eternal!"
"Then let this world and these nonsensical Hashira return to nothingness alongside me!"
Muzan's heavily mutilated body suddenly began to expand violently.
The completely out-of-control solar energy he had absorbed reacted violently with his foul demonic power.
His body transformed into an ever-expanding dark sun radiating an aura of absolute destruction.
It devoured light and matter, preparing to blow the entire Infinity Castle and everyone present into cosmic dust.
However, amidst this grand self-destruction, a tiny, nearly imperceptible chunk of flesh quietly detached from his expanding core.
It attempted to tear open a microscopic spatial rift to escape.
This was Muzan's true plan.