The Foundation: Starting by Inventing SCPs

As it walked, it said, "The stench of pestilence is everywhere in this world!"

"It needs proper treatment!"

"Perhaps I can find the perfect cure for the pestilence!"

At the thought, SCP-049, the Plague Doctor, grew so excited that it quickened its pace down the mountain.

Meanwhile, Muzan Kibutsuji, hiding in Infinity Castle, had learned everything happening outside from reports sent by other demons.

Muzan Kibutsuji was stunned!

A monster that had turned Tokyo into hell, a suit-clad brute who had slaughtered Lower Rank Five with one hand, ninjas who summoned lightning and fire, an ancient swordsman hunting down the Demon Slayer Corps...

And a bird-beaked doctor who could bring demons back to life!

What was happening to this world? Where had these people come from?

But that was not the point!

The point was that every one of these strangers was powerful enough to defeat him. And except for the bird-beaked doctor...

They all seemed to be looking for him!

Muzan Kibutsuji panicked. He knew what would happen if any of them found him.

Nothing good awaited him!

Without hesitation, he summoned every Upper-Rank Demon to Infinity Castle and ordered Nakime to seal it off completely.

He planned to hide there until they left.

At that moment, he was immensely grateful for Infinity Castle, a refuge separate from the rest of the world.

Without it, they might actually have found him.

That was Muzan Kibutsuji for you!

Against the weak, he struck without mercy. Against the strong, he cowered like a mouse!

He might have been the least imposing final boss in any battle manga.

At Demon Slayer Corps Headquarters, while Muzan Kibutsuji and the Upper-Rank Demons hid away in Infinity Castle, Kagaya Ubuyashiki sat in the place of honor, supported by his wife. Sores covered his face, and his brow furrowed as he listened to the Insect Hashira, Shinobu Kocho, report.

"My lord, according to the reports brought back by the Kasugai Crows, 142 Demon Slayer Corps branches have been destroyed by unidentified enemies. Not a single member stationed there survived. The death toll stands at 1,432."

Tears welled in Shinobu's pale violet eyes. She continued, "The Water Hashira, Giyu Tomioka, was also killed by the bird-beaked doctor and is believed to have been turned into a puppet."

"The Sound Hashira, Tengen Uzui, was killed alongside his three wives while trying to rescue an outpost. Their attacker was an ancient swordsman wielding the Black-and-White Twin Blades."

"After killing Tengen Uzui, the swordsman took on his appearance. He seems to have inherited Tengen's memories."

"He and his followers are now headed this way."

"The Love Hashira, Mitsuri Kanroji, was beaten to death by a group of ninjas with distinct cracks across their cheeks. She killed several of them during the fight."

"But no matter how badly they were wounded, they recovered soon afterward."

"Those ninjas then used Ninjutsu to resurrect Mitsuri."

"She has joined them and is leading them here. They'll likely arrive in about two hours."

By then, tears had completely blurred Shinobu's violet eyes. Ever since her sister Kanae had been killed by Doma, Upper Rank Two...

Shinobu had sealed away her feelings, keeping a smile on her face at all times, just as Kanae had.

But now she could hold it in no longer.

Only days ago, her comrades had gathered together, sharing stories of the demons they had slain. Now unknown enemies had killed them and turned them into puppets!

The blow broke Shinobu.

Even so, she forced herself to continue reporting to Kagaya Ubuyashiki. "The Serpent Hashira, Obanai Iguro, and the Former Flame Hashira, Shinjuro Rengoku, were defeated in Tokyo by a monster calling itself Meow-Meow."

"It forced a lump of flesh down each of their throats."

"Afterward, Obanai and Shinjuro turned into monsters and joined the slaughter of Tokyo's civilians!"

"They transformed large numbers of civilians into monsters, then set out for here as well."

"My lord..."

At Shinobu's words, Kagaya Ubuyashiki's already failing body gave out. A sweet taste rose in his throat, and he coughed up a mouthful of blood.

The remaining Hashira—Sanemi Shinazugawa, Gyomei Himejima, Muichiro Tokito, and Kyojuro Rengoku—went pale.

They rushed to Kagaya's side and watched anxiously as Amane gave him his medicine.

After drinking a few mouthfuls of the medicine his wife had prepared, Kagaya's complexion improved slightly. He addressed them. "Pass on my orders. Every member of the Demon Slayer Corps is to hide immediately, wherever they are."

"Until we know who these enemies are and what they want, all operations are suspended!"

"You must hide yourselves, too!"

Kagaya paused, then continued, "I will stay here and wait for them."

"I can tell they're looking for something."

Gyomei Himejima forgot all protocol and interjected, "My lord, let me stay with you!"

"If something goes wrong, I'll fight to the death—"

Kagaya cut him off. "No. You are the hope of the Demon Slayer Corps."

"My life is almost spent."

"Even if I leave, I won't live much longer!"

"I might as well make this broken body useful!"

They still stood there, determined to stay with him. For the first time, the usually gentle Kagaya lost his temper and shouted at them:

"Do you want me to die with regrets?"

"Go, now!"

"Go!"

Gyomei and the others wanted to stay and protect him. But they knew that, given their strength, staying would only mean dying alongside him.

At last, under Kagaya's stern orders, they knelt and bowed respectfully. Then they turned and streaked away, taking the surviving Demon Slayer Corps members with them.

They left Headquarters for the hiding places prepared in advance.

Once Gyomei and the others were gone, Kagaya turned to his wife, Amane. "Are the explosives ready?"

Kneeling beside him, Amane gently wiped the blood from the corner of his mouth. "They're ready."

"Thank you for everything."

Kagaya looked at the wife who had stayed beside him for more than a decade. His voice was full of regret. "You should have been revered as a divine maiden."

"Instead, you chose to stay with me and tirelessly care for someone as useless as I am."

"And now you have to die with me."

"If there is a next life, let me take care of you."

Amane shook her head and answered softly, "My husband is not useless. He is a true hero."

"I'm proud to have stood by your side and borne your children."

"To die alongside you today..."

"Is my honor."

Kagaya could hold back no longer. He drew Amane gently into his arms, stroked her hair, and said softly:

"With a wife like you, I can die without regret."

Amane listened to his faint heartbeat and rested in his embrace as they waited for the enemies who, in a single day...

Had thrown all of Japan into chaos.

Meanwhile, in the town below Mount Kumotori...

SCP-049, the Plague Doctor, surveyed the town, now a living hell, and the hundreds of SCP-049-2 behind it. As it packed away its surgical tools, it said with satisfaction, "Good. The pestilence here has been eliminated!"

"But I can feel it spreading through this world!"

"There are more patients out there who need our treatment!"

It paused, then continued, "To contain the pestilence, we must pick up the pace!"

"Come!"

"Let us treat more patients!"

Under the livestream viewers' gaze, SCP-049 led its vast army of SCP-049-2 toward the surrounding towns.

The viewers fell silent.

They knew SCP-049 had decided the entire world was infected with pestilence.

It would not stop until it had "treated" every "patient."

And no matter how many corpses SCP-049 operated on, the time it took barely changed. To it, one corpse or ten thousand...

Made little difference.

Either way, it could complete the procedures in just five or six minutes.

The Demon Slayer World was doomed.

At this rate, it would not take long.

SCP-049 would turn every living being in the Demon Slayer World into SCP-049-2, extinguishing all life and leaving it a forbidden land of the dead.

The viewers could only marvel.

An anomaly was an anomaly!

Even an intelligent anomaly like SCP-049 defied common sense!

Its abilities were far too bizarre!

They were beyond mortal comprehension!

On the livestream, viewers watched SCP-049 lead the hundreds of SCP-049-2 it had created toward the next town...

And sighed in unison.

They had seen that SCP-049 took roughly the same amount of time regardless of how many corpses it converted.

SCP-049-2 could not only wield all the strength they had possessed before death, but also use their abilities without limit or any apparent cost.

Everyone realized how badly they had underestimated the Plague Doctor.

Its surgeries had thoroughly sickened them, but they had still thought it far easier to deal with than SCP-173, Little Peanut, or SCP-096, Shy Guy.

Now, though...

All SCP-049 needed was enough corpses.

Its power would grow without limit, and that growth would be exponential. Unless it was contained the moment it appeared...

There would be no stopping it.

Give it even a little time to gather strength, and it could raise an army of SCP-049-2 to sweep across the universe.

An anomaly was an anomaly.