10 Years Later, the Demon King Appears in the Intermediate World and Gathers His Servants
The Demon King Kim Jae-hyun had descended upon the Intermediate World ten years after the Hero's arrival.
The entire continent had been at peace for a decade.
Ten years ago, the Demon King Laylana and the summoned Hero Kim Jae-hyun had clashed in another world. The Hero had sacrificed everything to bring down Laylana, and the world had been told that peace had come to the Intermediate World.
Although the Hero had vanished, most of the dark army composed of demons and monsters had already been wiped out by his hand. The surviving companions of Kim Jae-hyun still possessed overwhelming power and continued to rule over the continent.
Of the ten nations that had once existed on the continent, the Frank Kingdom, the Iberian Kingdom, and the Calmir Kingdom had been completely destroyed. The remaining seven nations, led by the strongest Habsburg Empire, had suffered devastating blows.
Especially in the battle against Demon King Laylana, humanity and the other races had been driven to the brink of extinction. As a final hope, they had summoned the Hero from another world, and the continent's population had been reduced to one-third of its previous size.
Yet the price of survival had refined the remaining humans into something far stronger.
After ten years of fighting against the dark army, their hard-won experience had forged unprecedented strength. Jason, Griffith, William, and Kyle—Kim Jae-hyun's former companions—now commanded power that even their kings could not match from within their respective countries.
Moreover, Saintess Lucretia, who had once been the Holy Maiden, commanded divine power far greater than before. As the Pope of the Holy Astraea Church, she wielded authority that surpassed even the Pontiff's.
They conducted regular purges, hunting down every demon, monster, and black mage left on the continent, and executed them without mercy.
Thanks to their efforts, the surviving demons, monsters, and black mages were forced to hide in remote wilderness areas, living in constant fear of discovery.
Even the seven nations that claimed to have stabilized the continent had placed bounties on demons, monsters, and black mages.
Especially the corpses of demons and monsters. Black mages burned with greed for such rare materials that could only be found in the Demon World—creatures far more scarce than ordinary monsters. Their value was correspondingly high.
The dark army that had once invaded the Intermediate World had become prey, hunted by humans instead.
Surviving black mages lived in the deepest, most isolated caves, their lives miserable and their days spent in constant hiding.
The black mage siblings Ron and Rin were no exception.
This year, the eighteen-year-old brother and seventeen-year-old sister had reached the late 5th Circle and mid-5th Circle respectively.
Back when Demon King Laylana had appeared, black mages had been able to contact demons directly. With their help, they had risen through the ranks of magic far faster than anyone.
Demons had granted them demonic energy through contracts and shared their magical knowledge. As a result, their advancement had been rapid.
But after ten years, the situation had changed. It had become nearly impossible to advance at the previous pace. Those who hid in the wilderness sometimes still received demonic energy from their hidden companions, yet many black mages had fallen far behind.
The Ron and Rin siblings had been only eight and seven years old when the Demon King's army had been defeated by the Hero Kim Jae-hyun.
Even then, they had burned with an insatiable desire for revenge. Despite their tender age, they had trained relentlessly, pushing their limits.
Their father had been a commoner who ran a small but successful trading company. Their mother had been strikingly beautiful.
And because she was beautiful, she had attracted the unwanted attention of Andrew, the second son of the Gray Baron.
Andrew had begun openly pursuing Ron and Rin's mother. The villagers' attitude toward the siblings' father had soured overnight.
People who had once smiled and greeted him warmly now avoided him and muttered curses about causing trouble for the village.
But that was not all.
The siblings had come to understand, bone-deep, how wicked humans could truly become.
Andrew had brought knights, arrested their father, and planted the absurd charge of secretly trading with black mages.
At the time, the Demon King's arrival had created chaos, and anyone linked to black mages faced immediate execution.
If their father had been convicted, he would have been killed on the spot.
Yet later, when the truth was revealed, villagers who had received money from Andrew had testified that they had witnessed the father trading with black mages. It was a lie so outrageous that no one would have believed it.
Nevertheless, Andrew had carried it out immediately. He had executed the father and dragged the mother into the bedroom by force.
Thanks to their mother's quick thinking in hiding the children, Ron and Rin had barely escaped with their lives.
At only five and four years old, they had understood that if captured, they would become hostages used to threaten their mother. She would be trapped forever by this monster.
Running away, they had accidentally encountered a black mage. The siblings had clung to him, begging him to take them as disciples.
Having already witnessed humanity's darkest side, they had turned their hatred toward the world itself. They had sworn to become black mages, join the Demon King's army, and shatter this world to its core.
Among the black mages, many had joined for power, and many more for the same hatred and despair. The siblings had naturally slipped into that group despite their young age.
They had no deep loyalty to one another, but they shared a burning desire to destroy the world. They were not driven by petty greed like ordinary power-hungry mages. Instead, they had trained hard and accepted every lesson from the black mages who took them in.
They had received knowledge of black magic and demonic energy, along with secret grimoires left by fallen black mages.
Those grimoires could be freely accessed and stored using spatial magic engraved on the ring-shaped artifacts created by demons. As late 3rd Circle black mages, they had performed well in battle, operating from the rear, and had avenged themselves by destroying the village that had betrayed and sold out their family.
But that fateful day ten years ago, when Demon King Laylana had perished alongside the Hero Kim Jae-hyun, everything had changed.
The mighty Demon King's army had collapsed. Ron and Rin had come to hate the Hero who had killed the Demon King, and they had spent the next decade hiding while quietly advancing their magic to reach the 5th Circle.
Today, right in front of them, he had appeared.
"What a fortunate timing. To find a black mage here."
The youth before them had jet-black hair and an impossibly beautiful face. He was the Hero Kim Jae-hyun, summoned from another world.
Any black mage who had served under the Demon King would know exactly who he was. He had slaughtered the higher-ranking black mages with that cursed Holy Sword. Even many mid-tier black mages had fallen to the aftershocks of his attacks.
For Ron and Rin, he was the most terrifying and hateful enemy imaginable—the Hero who had killed the Demon King and blocked their path to revenge.
Yet here he stood, alive and well. The siblings felt first a surge of fear, then a wave of rage.
"Hero!"
Ron, the older brother, shouted first and hurled a spell at him.
"How insolent."
But the moment Kim Jae-hyun's crimson eyes flashed, Ron and Rin found themselves involuntarily dropping to their knees, foreheads pressed to the ground.
"Krrrk!"
"Kyaah!"
Kim Jae-hyun lifted his head and looked down at the two trembling black mages with an arrogant, cold smile. Behind him stood two breathtakingly beautiful women—Selina and Lucien—silently at attention, faces completely expressionless. Yet their eyes betrayed a flicker of surprise.
That he had shown such mercy to the insolent Ron and Rin by sparing their lives was astonishing. But as their guide, they quickly dismissed it, convinced it was merely an unexpected act of kindness.
And it was far more than that.
"Remember this well. I am the Demon King who rules the Demon World, the one who will bring ruin to this cursed world through revenge."
Kim Jae-hyun spoke while pressing his foot firmly onto Ron's outstretched hand, grinding it into the dirt.
"C-croaaagh!"
The grinding pain of his bones cracking made Ron bite through his lip until blood filled his mouth, yet he endured it. Black mages who had gained power through contracts with demons could never resist a Demon King. Submission was the only option when facing him.
"Hahaha! Now that you mention it, I remember. Many black mages in this world were people who had despaired, hated everything, and felt completely abandoned. Some chose to become trash, but others decided to turn the world itself upside down."
His voice carried genuine amusement. To Ron and Rin, it sounded like mockery. But it was not mockery at all.
"You are extremely similar to me. You must hate the world too, just as I do. You want to destroy it, don't you? How about it? Why don't we join forces under me and shatter this cursed world?"
Kim Jae-hyun's tone was seductive, pure temptation—the very image of a demon far removed from the noble Hero.
Both siblings looked up at him in a daze. They felt it clearly: he was one of them. Even though he smiled, his eyes burned with an insane hatred for the world, and his endless thirst for revenge ran deeper than their own.
"As Demon King, I swear this. I hate and despise this world. That is why I have come to this Intermediate World to bring its end. Kneel before me. Serve me. Before any oath of loyalty to me as Demon King or black mage, submit to me in order to fulfill my revenge and help me achieve it."
Kim Jae-hyun had moved beyond the master-disciple relationship and demanded a lord-subordinate bond born of shared purpose. The ten years of hiding had left Ron and Rin with no hesitation in their answer.
"We will obey! We swear our loyalty!"
Both siblings immediately bowed their heads again and swore their allegiance. The suppressed madness of revenge in their hearts began to stir once more.