Kyoto.
Boom, boom, boom.
A series of explosions lit up half the sky with fiery glows, the shockwaves rippling outward for over ten miles.
Swish.
Landing on the ridge of a grand mansion, Genya and Zenitsu stared at the towering flames in the distance, their expressions filled with shock.
After a moment, Genya muttered, "How did they do that? Dynamite?"
Zenitsu shook his head. "They passed right under our noses. They weren't carrying any explosives!"
Genya's face flickered with uncertainty. "Haku's definitely hiding something. That guy with him isn't even a Demon Slayer swordsman!"
"Yeah, just charging into a demonic lair like that—what are they up to? They can't possibly think they can clear out a whole city of demons, right?" Zenitsu was equally puzzled.
"Huh!?" Genya suddenly let out a soft exclamation.
Zenitsu quickly followed his gaze. The blazing orange-red flames in the distance dimmed abruptly, not because they were extinguishing, but because they inexplicably turned into black flames, burning even fiercer!
The two exchanged stunned glances.
Zenitsu asked, "Have you ever seen black flames like that?"
"Tch!" Genya spat. "Never even heard of them!"
...
On the Battlefield.
Surrounded by a dense swarm of demons engulfed in his Amaterasu black flames, Sasuke's expression was cold and unyielding.
Haku, standing nearby, asked with concern, "Will your dojutsu hold up?"
Sasuke replied, "For the sake of the shinobi world's safety, a little dojutsu strain is nothing. C, once my Amaterasu burns a gap, we charge in!"
"Got it!" Haku nodded, warily scanning their surroundings.
Beneath his mask, Sasuke's scarlet Mangekyo Sharingan surveyed the area.
Like Haku when he first arrived in the Demon Slayer world, Sasuke found the demons here far weaker than the Upper Rank demons that invaded the shinobi world.
He had prepared for a life-or-death battle, but upon entering the city, he discovered the demons were pitifully weak. Aside from their demonic regenerative abilities, they were practically useless.
The only surprise was their sheer numbers.
Amaterasu's black flames were naturally effective against demons, much like a Nichirin Blade—flames that could truly kill them. As the flames spread, the demons clogging the streets fell in droves, reduced to ash amid wails and roars.
"Go!" Seeing his Amaterasu carve a path, Sasuke flashed forward, speeding toward the city's depths.
Haku touched the pouch of Type-4 Aging Serum at his waist and followed.
For this split operation, Shinji had equipped each team with multiple doses of the serum to counter the mysterious figure, the Demon King.
Swish.
The two moved swiftly, crossing several streets in a blur, like phantoms delving deeper into the city.
Moments later, they stopped before a shrine.
Sasuke said, "Something's off here."
"Agreed," Haku nodded lightly.
Though he lacked dojutsu or the Transparent World of Breathing Styles, his instincts told him this place was wrong.
Sasuke's lips curled. "I hope the Demon King's here."
In the distance, Genya and Zenitsu had quietly followed, crouching on rooftops, dodging the city's scattered demons while observing Sasuke and Haku.
Zenitsu said, "They've stopped!"
Genya asked, "What is that place?"
Zenitsu shook his head. "No idea. Looks like a shrine."
Boom, boom, boom.
Suddenly, the ground trembled, the vibrations growing stronger, as if an earthquake or tsunami were striking.
"What's happening!?" Genya and Zenitsu, perched on the rooftop, were startled.
Then, the ground before the shrine split open, the crack rapidly spreading outward, widening into a bottomless chasm in moments.
Boom.
With a thunderous roar, a massive arm emerged from the chasm. A house-sized hand pressed against the ground, pulling up a colossal shadow.
The mountainous figure, reeking of a foul stench, climbed out with agility defying its size. Genya and Zenitsu were so shocked they nearly forgot to breathe.
"How… how is this possible!?"
"What kind of monster is that? Is it what turned Kyoto into a demonic lair?"
Questions and exclamations flooded their minds.
Even as Hashira, elite members of the Demon Slayer Corps, the sight of this behemoth made them tremble, gripped by instinctual fear.
Against such a creature, their Nichirin Blades were like toothpicks, barely fit to scratch it!
"Run!" The two reached a silent agreement.
Staying would mean certain death, so they had to relay this intelligence—there was a disaster-level monster lurking in the depths of the demonic lair!
But as they prepared to flee, they noticed Sasuke and Haku, standing outside the shrine, weren't panicking. They stood calmly, seemingly sizing up the unknown behemoth emerging from the chasm.
"Are they insane?" Genya and Zenitsu exchanged confused glances.
On the battlefield, Sasuke snorted lightly. "You'd better be the Demon King!"
Without hesitation, he activated Susanoo. A purple shadow projected from his body, swiftly forming a half-bodied, armored giant wielding a bow.
Roar!
With a bellow, Sasuke's purple Susanoo drew its bow and fired. Swish. A purple arrow shot forth, piercing the behemoth's head with a shrill whistle, staggering it.
"This!?" Genya and Zenitsu, poised to flee, froze in place.
Staring dumbfounded at Sasuke's Susanoo, they couldn't tell if they'd fallen into some illusion, their minds bewitched.
The behemoth, its head blasted open by Susanoo's arrow, swayed but stood upright, its head rapidly regenerating.
Sasuke smirked at the sight. "Now that's more like it!"
Haku cautioned, "Be careful. This monster's no ordinary foe."
"I'd be disappointed if it was. If it's not the Demon King, I'm wasting my time!" Sasuke's lips curved into a signature Uchiha smirk.