The battlefield had reached a fever pitch of intensity and ferocity.
Burning with the last of their strength and the full force of their will, the Hashira swarmed the terrifying Demon King, Muzan Kibutsuji.
The night air sang with the sharp hiss of Nichirin steel and the brilliant, elemental flares of their breathing techniques, a constant storm crashing against the violent dance of Muzan's black whips and bone-sharp blades.
As the ancestor of all demons, Muzan's strength was unfathomable.
Even while besieged, every counterattack he launched carried a deadly threat.
A fresh, bloody wound had been torn across Sanemi's chest.
Giyu who was forced to repeatedly use the Eleventh Form, Dead Calm, to protect his comrades, was growing pale from the immense stamina drain.
Kyojuro Rengoku's flames no longer burned with the same intensity they had at the start.
Every Hashira now bore new scars.
But their attacks were not in vain.
While Muzan held the upper hand, the Hashira were the pinnacle of humanity's strength.
If one sword strike failed, two would follow.
If two failed, then ten.
Muzan's regeneration, though terrifying, was not infinite.
Under the combined assault of the potent toxins now raging through his body and the relentless, unending slashes of the Hashira, he would, sooner or later, reach his limit.
Muzan knew this as well.
But he was not panicked.
He was prepared.
Clang.
The strange, resonant twang of a biwa, nearly lost in the roar of battle, suddenly echoed in everyone's minds.
A cold, triumphant arc curled Muzan's lips.
"Tonight, the Demon Slayer Corps ends."
The next moment, the air at multiple points around the battlefield twisted and rippled like the surface of a pond.
An extremely ominous premonition washed over the Hashira, as cold as ice water.
BOOM!
An incredibly dense and terrifying demonic aura erupted first.
Space shattered like a mirror, and a tall figure in the purple robes of an ancient warrior stepped through.
Six cold, scarlet eyes surveyed the battlefield.
It was Kokushibo the Upper Moon One.
His very presence seemed to freeze the air, the immense pressure of a centuries-old master swordsman putting every slayer on edge.
Swish~
With a pleasant chime of condensing ice, Douma, Upper Moon Two, stepped gracefully from another spatial tear amidst a shower of colorful ice flowers.
His rainbow-colored eyes swept the scene and when he saw Kanae Kocho with a smear of blood on her lips, his serene smile widened.
"Ah, the beautiful butterfly is here as well! What a fateful reunion. We can still be friends, you know."
BOOM!
Like the beating of a war drum, a demonic presence filled with the ultimate desire for combat descended.
Akaza, Upper Moon Three, his bare torso covered in the dark blue lines of his power, his body brimming with explosive force.
His eyes immediately locked onto the pale-faced Giyu Tomioka, a thrilled smile spreading across his face.
"Tomioka Giyu! I can feel it! Your fighting spirit is even stronger than before!"
Immediately after, two more figures emerged.
One was the burly, taciturn Maito, Upper Moon Four.
His muscular arms were folded, his golden eyes glaring with the savage aura of a wild beast.
The other, Lee, Upper Moon Five, was a ghostly, indistinct figure hidden beneath a gray robe, her presence strange and unpredictable.
Finally, quietly crawling up from a shadow, came Kamaro.
He made no move to join the battle, instead watching with the detached interest of a spectator appreciating a well-staged play.
All the Upper Moons had arrived.
And they were not alone.
From the darkness surrounding the ruined Moriki Manor, hundreds of lesser demons began to emerge, their blood-red eyes glowing like embers.
The battle had just become a war.
"This," Giyu Tomioka said, his expression grim, "is going to be difficult."
No one disagreed, but not a single Hashira faltered.
Their grips only tightened on their swords.
Seeing their unbroken resolve, Muzan sneered and gave a single, simple command.
"Crush them."
As the strongest of the Upper Moons, Kokushibo's six eyes locked onto the two he deemed the most powerful swordsmen: Gyomei Himejima and Sanemi Shinazugawa.
"To have such strength at your age," he murmured, his voice a cold rasp as he slowly drew his grotesque, fleshy katana.
"A pity."
Douma waved his golden fans, and a blizzard of ice lotuses descended upon Kanae Kocho and the injured Kanroji Mitsuri.
"Two lovely ladies! Allow me to be your opponent."
Akaza laughed with pure excitement, leaping and slamming his feet into the ground, a massive snowflake-shaped shockwave erupting from the impact.
A dark blue aura of pure fighting spirit soared as he shot toward Giyu.
"Come, Tomioka Giyu! Let us have a battle to the death!"
But Kyojuro Rengoku was already there, his blade of fire meeting Akaza's charge alongside Giyu's stream of water.
Maito and Lee, without a word, rushed towards the remaining Hashira.
"I'll give you a flamboyant end!" Uzui Tengen roared, hurling several small, powerful gunpowder bombs that engulfed Maito in a brilliant explosion.
Through the smoke, a coiling, purple blade followed with the precision of a striking snake.
"Hurry up and die," Iguro Obanai hissed. "I need to go help Mitsuri."
Elsewhere, the ghostly Lee was intercepted by another, even faster purple figure.
Shinobu's violet eyes flickered with complex emotions as she faced the other demon.
Without a word, their two demonic auras flared, and they rushed at each other.
As the all-out war exploded, Kamaro quietly melted back into the darkness.
'Interesting, so very interesting,' he thought. 'I wonder who will be the first to die? Hehe…'
.....
At that same moment, miles away…
A pungent, chemical smell, the smell of gunpowder, suddenly hit Shinichi's nose.
He raised his head.
Through the trees, he could just make out the distant, dark silhouette of the Moriki Manor.
The ominous premonition in his heart was now a raging certainty.