Just as the duel between Shinichi and Maito reached its terrifying climax and the surging river of blood about to swallow Shinichi whole—
"DAMN IT! AM I LATE?!"
A furious, excited roar echoed from the edge of the battlefield.
A bare-chested young man wearing a rugged wild boar hood, his jagged Nichirin blades resting on his shoulders, took in the chaotic scene for a split second before letting out a joyous battle cry.
"PIG ASSAULT!"
He then charged into the fray with astonishing speed, his blades a whirlwind of flashing steel as he carved through a dozen lesser demons as if they were vegetables.
"S-s-so many demons! How can there be so many?!" Zenitsu Agatsuma trembled, his hand gripping his sword so tightly his knuckles were white.
But then he remembered his master's final words of encouragement.
He took a shaky breath, squeezed his eyes shut, and the world went silent.
When he opened them, the fear was gone, replaced by a cold, deadly focus.
"Thunder Breathing, First Form: Thunderclap and Flash."
Sizzle!
A single, brilliant streak of lightning cut through the darkness, weaving a trail of death through the demon horde.
Finally, the boy with the scar on his forehead, Tanjiro Kamado, followed his companions onto the battlefield.
The moment he arrived, his gaze was drawn as if by a magnet, locking onto the figure at the heart of the battle who radiated an aura as deep and terrifying as the abyss—Kibutsuji Muzan.
At that moment, Muzan was watching the battles with growing irritation.
While his strongest Upper Moons held the advantage, the newer ones were struggling.
He had not come here for a battle of equals.
He had come for a swift, devastating annihilation of this entire, annoying organization.
It was then that he noticed something. His scarlet eyes swept casually across the new arrivals and stopped.
A red-haired boy instantly seized his attention.
'Huh? That disgusting aura…'
"That… that's… Muzan!!!"
The moment Tanjiro saw him, his eyes went blood-red with a torrent of pure, undiluted hatred.
The images of his family's slaughter on that snowy night, Nezuko's painful transformation, the hardships, the sacrifices… it all erupted in a single, heart-wrenching roar.
"MUZAN—!!!"
Ignoring everything else, he charged.
The Hinokami Kagura, the legendary Breath of the Sun inherited from his father, exploded from him as he shot toward the Demon King like an arrow loosed from a bow.
"FOR MY FAMILY! FOR NEZUKO! FOR EVERYONE! DIE!"
"Hm?" Muzan's eyes shifted slightly. He effortlessly sidestepped Tanjiro's furious slash and looked at the boy's face, at the familiar hanafuda earrings dangling from his ears.
A dusty, hated memory was triggered.
"You… the brat with the sun-earrings. Damn you. The sight of those things makes me sick." His body twitched.
'That man has been dead for centuries, yet a breath that even faintly resembles his still makes me want to split apart and flee. Humiliating!'
But then, he remembered something more important.
Tanjiro's words.
His eyes suddenly lit with a greedy, feverish light.
"You… the girl named Nezuko… your sister! Where is she?! TELL ME!"
The Demon that conquered the sun.
That was his ultimate goal.
And the final clue was standing right in front of him.
In an instant, Muzan's focus shifted entirely.
He unleashed the full force of his terrifying, murderous aura.
"Capture the boy with the sun-earrings!" he commanded the nearby demons.
At the same time, his own bladed whips shot out like striking pythons, not just at Tanjiro, but at Zenitsu and Inosuke who were rushing to support him.
"Breath of the Beast, Fifth Fang: Crazy Cutting!" Inosuke's twin blades became a chaotic vortex of steel, shredding the whips.
Tanjiro himself, weaving between the attacks with the fluid movements of Water Breathing while countering with the explosive power of the Sun Breathing, continued his relentless advance.
He had eyes only for Muzan.
But Muzan's outburst unleashed a bloody storm.
While the trio could hold their own, the ordinary slayers were not so lucky.
In seconds, several were torn to pieces by his whips.
....
At that same instant, on the other side of the battlefield…
Faced with Maito's "Blood River Burial," an all-or-nothing attack that left his back completely exposed to Tengen and Iguro, Shinichi entered a state of absolute mental clarity.
The demonic energy Maito had been forcing into his body was no longer a poison, but a stimulant, pushing his Breath of the Forest into a violent collision with its opposite: death and destruction.
His master's words, Mitsuyo's final reminders, it all became clear.
Life isn't just growth; it encompasses decay.
Creation requires destruction.
The ultimate form of Forest Breathing wasn't just about harnessing vitality; it was about commanding the entire cycle of life and death itself.
As the blood-red river was about to consume him, the green light on his body retracted.
In its place, a new breath—deeper, more majestic, containing the origin of all life—awakened.
It was not green, but a soft, white halo that held all the colors of life within it, warm and vast.
He slowly raised his blades, their usual colors gone, replaced by a pure, gentle white.
He did not call out a technique.
He simply followed the new rhythm in his soul and slashed.
There was almost no sound.
The soft white light met the roaring river of blood.
And like snow under a summer sun, the all-consuming torrent of death simply… dissolved.
The violent demonic energy, the will to destroy, all of it was purified, returned to nothingness.
The blade's light continued forward, gently brushing across Maito's body.
The ferocious expression on Maito's face froze.
The boiling demonic energy within him was extinguished like a snuffed flame.
His blood armor crumbled into dust.
His forward momentum ceased, and with a soft thud, his massive body, drained of all power, knelt on the scorched earth.
"Shunichi…" he whispered, a strange, satisfied smile on his face as his body began to disintegrate.
"This kid… he's surpassed you. He's actually realized it… the Breath of Life…"