Fifty years after Kibutsuji Muzan became the King of Demons, the clan to which he had once been bound by blood — the Kibutsuji family — was struck by calamity.
A strange, sudden illness swept through the bloodline. No matter how many physicians were summoned, not one could identify, let alone cure, the mysterious disease.
The affliction gave no warning. Those who laughed and spoke with their kin one moment would fall silent and lifeless the next. Death moved like a shadow among them, claiming every soul that bore the blood of the once-noble Kibutsuji. None were spared.
Within months, the great and ancient Kibutsuji family — a house of wealth and influence that had stood for centuries — vanished entirely from the records of history.
From the Kibutsuji line had branched another: the Ubuyashiki clan, descendants who had taken a new name generations prior and built renown in Kyoto.
When word reached them that the parent family had perished overnight, they were shaken to their core. The strange disease had manifested only within the Kibutsuji estate — nowhere else in the region.
The Ubuyashiki sent men to investigate, but what they found defied reason.
First: the illness affected only those of Kibutsuji blood. Outsiders remained completely untouched.
Second: the cause was impossible to trace. No physician could diagnose it, much less treat or ease it.
And third: the disease struck without warning — sudden, fatal, absolute.
The Ubuyashiki patriarch and his kin were left in deep confusion.
Could it have been vengeance? Impossible. The Kibutsuji name had stood for hundreds of years, its fortune and influence vast. No enemy could have destroyed such a family without leaving a trace.
Still, the mystery of their fall haunted the Ubuyashiki for generations.
Two Hundred Years Later
Another calamity befell them.
The elders of the Ubuyashiki clan began to wither prematurely — their bodies aging decades in mere years. Newborns were frail, many stillborn or sickly beyond recovery.
At first, the family dismissed it as a fortune. But when their elders died in rapid succession and the next generation dwindled, they understood too late: something unnatural was at work.
Within decades, the Ubuyashiki stood on the brink of extinction.
Fifty years later, a young man named Ichirō Ubuyashiki, barely twenty-one, assumed leadership — the youngest head in the family's long history.
Desperate for answers, the Ubuyashiki prayed, searched, and begged the shrines for help.
Then one day, a messenger arrived from the Fujiwara family, a clan of priests serving the great shrine of Amaterasu in Kyoto. Their patriarch, Fujiwara no Ki, came in person.
"Amaterasu has revealed the cause of your clan's suffering," said Fujiwara no Ki without preamble as he stood before the young head.
Ichirō, seated in the cold and silent reception room, lifted weary eyes to him. The air in the Ubuyashiki household was heavy with grief and despair — the atmosphere of a family long overshadowed by death.
"Then, Lord Fujiwara," Ichirō said solemnly, "please tell me the reason."
Fujiwara's expression did not waver.
"What plagues your family is not illness… it is a curse — one born from your own bloodline. That is why your people wither so swiftly."
Ichirō's brow furrowed. "A curse? From where could such a thing come?"
"From the gods themselves," Fujiwara replied. "A divine curse upon your blood."
"Gods…?" Ichirō murmured. "Do they truly exist?"
"As long as faith exists," said Fujiwara, "so too do the gods."
Ichirō pressed, voice quiet but urgent. "If that is so, then what sin did our ancestors commit to bring such wrath upon us?"
Fujiwara's gaze hardened.
"More than a hundred years ago, the Kibutsuji clan bore a child, frail and close to death. In a desperate bid to save him, a physician devised an experimental elixir. But that medicine… wrought irreversible change."
He paused before continuing, his tone low.
"The child became a monster — a creature that feared the sun and survived only by devouring humans. That child was none other than a member of the Kibutsuji line: Kibutsuji Muzan."
Ichirō froze. "Kibutsuji… Muzan…?"
Naturally, you would not know the name," Fujiwara said softly. Centuries have passed. No one could have foreseen that the dying child would become a man-eating demon. I call such creatures oni — man-eaters."
Ichirō pressed a hand to his temple, overwhelmed. "A man-eating demon…? Forgive me, Lord Fujiwara, but such tales are difficult to accept."
Fujiwara's tone grew grave.
"Kibutsuji Muzan was the first of his kind — the progenitor of all demons. His blood carries the power to create more of his ilk, transforming humans into monsters who feast upon their own kind. Countless innocent lives have perished because of him. Every demon's sin can be traced back to that single origin — to your ancestor."
The weight of his words filled the room. Ichirō fell silent, his face pale.
Fujiwara continued, unflinching.
"According to the divine revelation, the curse upon the Ubuyashiki can be lifted only through atonement. The burden your clan bears is the consequence of your ancestor's creation — and only by destroying the Demon King, Kibutsuji Muzan, and all who follow him, can your family be freed."
Ichirō closed his eyes. For a long moment, neither man spoke.
Fujiwara, understanding his need for silence, lifted his cup of tea and drank. When he finally set it down, Ichirō spoke again, voice steady but somber.
"The tale you tell defies belief, and yet… I see no reason you would deceive us. Our clan stands at the edge of extinction. If this is truly the gods' decree, then we must face it."
He hesitated, then added quietly, "But even if we wished to fight… There are so few of us left. I am young, and my only son is but fourteen. We have neither the strength nor the numbers…"
Fujiwara inclined his head slightly, a faint smile crossing his face.
"Do not despair, Lord Ubuyashiki. The Fujiwara bear traces of divine blood, however faint, and we have served Amaterasu for generations. If a union is formed between our families — if the blood of the Ubuyashiki mingles with that of the Fujiwara — your descendants will be born strong, free of the curse's weakness."
Ichirō's eyes widened. "You mean…?"
Fujiwara's gaze held his, unwavering.
"Yes. Through this union, the gods may yet grant your bloodline a future."