Chapter 19: The Origin of the Demon King and His Demons
Yes—it was true.
In this world, things were not as Yukinoshita Akira had initially assumed. Neither Kibutsuji Muzan nor the demons he led were native to this reality.
And no, this wasn't a fusion world born from merging with the world of Demon Slayer.
Kibutsuji Muzan had arrived here abruptly, just three months ago, in the heart of this world's modern civilization.
He didn't come alone. The Six Upper Moons and Six Lower Moons—members of the Twelve Kizuki—had also manifested alongside him.
After spending some time assessing the environment and observing the state of this new era, Muzan nearly lost his mind.
Humanity here had evolved to terrifying levels. Modern weapons, automatic rifles, ballistic missiles, atomic bombs, even nuclear warheads...
For all his pride and inflated ego, Muzan was, at his core, a coward—one who only wore the mask of a king.
The moment he realized how dangerous this world truly was, he did what he always did best: he vanished.
He slipped into the shadows, hiding without shame. Remaining unseen for as long as it took.
Just like back then—when he ran from Yoriichi Tsugikuni and chose to remain hidden for decades, waiting until the strongest Demon Slayer finally died of old age. Only then did Muzan feel safe.
This time was no different.
Until he discovered a way to secure his own survival, he would not dare expose himself.
For over a month, he studied the country where he had first appeared. To his surprise, it was still called Japan, just like in the world he once ruled from the shadows.
Even the recorded historical periods aligned with the timeline of his origin.
From this, Muzan began to suspect that he had not crossed into another dimension—but had instead traveled forward in time.
With the Twelve Kizuki under his command, there was no need for him to act personally. He remained behind the curtain, reclaiming his role as the unseen ruler of darkness.
Except for Upper Moon One, whom he kept close, the rest of the Twelve Kizuki were sent out to scout and expand their reach.
Through his blood, he began converting modern humans into new demons—quietly rebuilding his demonic empire from the darkness.
But in the modern world, things were no longer so simple.
Surveillance cameras were everywhere. Population records were near-perfect. Turning humans into demons or hunting in plain sight was nearly impossible.
Every move had to be made in absolute secrecy. A single mistake, a single exposed clue—and Muzan would be erased before he could react.
He underestimated humanity's physical strength—but not the weapons they had created.
Fortunately, in modern Japan, reports of suicide and people dying alone were common. This provided a convenient cover for demon activity without raising suspicion.
Even so, as the "Rat King of Shadows," Muzan's obsession with the Blue Spider Lily had not diminished in the slightest.
Every demon he created was given two missions: grow stronger in silence—and search for the elusive Blue Spider Lily wherever it might exist.
Inside the villa he now called home, even without light, Muzan and Akaza could see perfectly. They were demons—this was their domain.
"By the way," Muzan murmured softly, "one of the demons just died."
"What?" Akaza's voice was laced with surprise.
In the past three months, not a single demon had been killed.
Sure, this world had terrifying weapons, but the humans here weren't that much stronger than the ones from their original world. In fact, some of them seemed even weaker.
More importantly, there was no Demon Slayer Corps. No Breathing Techniques. No Nichirin Blades. No Hashira.
Without those threats, demons should've been able to grow unopposed—without fear of being hunted.
And yet, one of them had died. Truly died.
Akaza couldn't help but wonder—was there some unknown force at play in this world?
It wasn't an unreasonable suspicion. Even in their original world, the existence of demon hunters had long remained hidden from the general public.
"Muzan-sama... does this mean... a new enemy has appeared?"
"No," Muzan replied flatly. "That fool simply spoke my name."
His expression darkened.
As the supreme ruler of demons, he would never tolerate anything that sullied his dignity. No demon was allowed to speak his name in vain.
"That's... unbelievable," Akaza muttered under his breath.
Even he hadn't expected such foolishness. Every demon who had received Muzan's blood instinctively feared him.
Muzan's blood was not a gift. It was a curse—a curse that ensured total submission.
(Note: Blood Curse — When a demon speaks Muzan's name aloud, the curse activates. However, due to the distance and the victim being a weak demon, Muzan hadn't sensed the moment it happened in full.)
What Muzan and Akaza didn't know was that the so-called "foolish demon" had simply been a petty coward. Fueled by jealousy and arrogance, he had tried to get revenge on a girl—only to run into a real monster and be utterly destroyed.
"The search for the Blue Spider Lily must continue. No delays," Muzan said coldly.
"Yes, Muzan-sama."
Akaza lowered his head in deep reverence. Orders from Muzan were absolute. No one argued.
"You may leave now."
"As you command."
Akaza bowed once more. Then his body melted into the darkness, vanishing without a sound.
This modern era was far more dangerous than the one they came from. In order to maximize their reach, the members of the Twelve Kizuki had been scattered across the country.
But Chiba City, the place where Muzan first appeared, had been declared their main base of operations.
It was here that he chose to dwell—in silence, in secrecy—watching the world from the shadows.
Besides himself and Akaza, another key figure also remained in Chiba:
Upper Moon One — Kokushibo.
Only a handful of lesser demons operated in this area. Open human hunting was impossible in today's surveillance-driven society.
And Muzan, ever the coward, would never risk exposure.
But the fewer humans they consumed, the slower their power would grow.
"I will find the Blue Spider Lily... no matter what it takes."
"With that flower... I will become the ultimate being. Perfection—true perfection."
His crimson eyes glowed in the dark.
Muzan's obsession had lasted for thousands of years. His hatred for the sun. His desperation to escape weakness. His endless fear of the light.
He knew the pain of living in darkness. He knew the agony of being vulnerable.
For a coward like him, such a flaw was unacceptable.
But now, fate had given him a new chance. A world with untapped secrets. A future filled with potential.
He believed the Blue Spider Lily existed in this world.
And this time, he wouldn't fail.
He would walk beneath the sun.
He would live forever.
He would become the True Demon King.
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