Crossover: The Problematic Deity of Arcadia

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Rui's head hit the ground with a dull thud, rolled once in the dirt—and yet, not a trace of anger appeared on his face. In fact, he looked... apologetic.

"I deeply apologize, Lord Muzan. I failed to recognize you immediately."

A severed head, speaking so sincerely, apologizing to the person who ripped it off—the sight was straight-up bizarre.

At least to Kanae, it felt downright surreal. Was this demon Rui into something weird…? Who apologizes after getting their head torn off?

But what Kanae didn't know was: for Rui, this was just another day in the life.

When it came to the ever-unpredictable Muzan Kibutsuji, losing your head was about as casual as being told "hi." It was practically a greeting.

Among demons—who couldn't die unless under very specific conditions—the only being capable of killing them outright was the original demon himself: Muzan.

And when he was actually mad, he didn't just twist your head off—he'd make the demon blood inside you explode, erasing you completely.

So, in Rui's mind, not recognizing Muzan's new appearance right away? That was already skating dangerously close to a death sentence.

He'd seen it before—demons killed on the spot for something as minor as not bowing fast enough, or missing Muzan's presence altogether. Compared to that, he had tried to pretend Muzan wasn't even there. He was honestly surprised he was still alive.

At that moment, Ryo smiled kindly and spoke gently to him: "You did well, Rui."

"Thank you for your praise," Rui replied sincerely.

His decapitated body crouched down, picked up his head, and reattached it to his neck like it was no big deal. Within seconds, the wound had fully healed. Even though Kanae had seen demon regeneration many times, it still unsettled her.

Compared to the Demon Slayer Corps—where one injury could mean death—demons had a ridiculous advantage. Only sunlight, wisteria poison, or a Nichirin blade to the neck could kill them.

No wonder the Corps had such a high mortality rate.

In fact, it was partly that endless cycle of loss that made Kanae consider the possibility of peaceful coexistence. Maybe there was another way.

While Rui was busy healing, Ryo turned his gaze to a female demon nearby.

Rui's eyes followed—he had no idea why Muzan-sama would pay any attention to his so-called "mother."

Not that he cared much for her.

Sure, he called her "Mother," but the woman was nothing more than a weakling who latched onto him, a low-tier demon he'd enhanced using blood granted by Muzan. Her death wouldn't mean anything to him.

Ryo smiled sweetly as he looked at the terrified female demon and said:

"Well, well… You've never eaten a human before, have you?"

The demon flinched hard, trembling in fear. Her voice shook as she begged:

"I-I'm so sorry! Truly sorry! I'm just… so weak. I didn't mean to—really, I didn't!"

Rui wasn't surprised. She had only become part of his "family" within the last week. Before that, she hadn't even dared to hunt humans—she was just a coward who always ran away.

So never having eaten anyone was… actually pretty normal for her.

But to Kanae, this was eye-opening.

A demon that had never eaten a human? That was practically legendary—like finding an ultra-rare SSR.

She had seen plenty of man-eating demons, and none of them ever gave up their appetite for flesh. But maybe—just maybe—a demon that had never tasted blood could coexist with humans?

As hope stirred in her chest, Ryo walked up to the girl, hooked a finger under her chin, and gently lifted her head.

"Never eaten a human, huh? That's no good at all."

The girl shook with terror, her eyes brimming with tears. "I-I'm sorry… I'm just not strong enough…"

"Is it really weakness?" Ryo's eyes narrowed slightly.

—[Authority: Demon]!

"Ugh—!"

The white-haired girl suddenly cried out in pain, eyes wide, mouth agape in a silent scream.

Her pupils turned gold. A small white horn sprouted from her forehead. Her aura changed completely.

Dark lightning crackled faintly around her body.

Fwoom—!

The very air trembled under the weight of her pressure.

Rui and Kanae instinctively backed away, eyes wide with shock.

Every instinct in their bodies screamed: Run. Whatever was being born in front of them wasn't just dangerous—it was a monster.

But neither of them dared to move too far—not while Ryo was watching.

Then he whispered a single word: "Disperse."

Instantly, the crushing aura shattered and vanished. The female demon collapsed, only to crawl up seconds later and nestle obediently by Ryo's feet like a docile lamb.

Rui didn't say a word. He couldn't.

If someone told him that the man in front of him wasn't Muzan Kibutsuji, Rui would punch that person's face into the dirt himself.

To take a throwaway demon and elevate her to a level that he, one of the Lower Kizuki Five, actually feared?

If this wasn't Muzan, then Rui would chop off his own head and kick it like a ball.

No doubt about it—this was Muzan Kibutsuji.

Meanwhile, Ryo looked down at the girl with a curious smile.

"Fascinating… A seven-digit spiritual class? Maybe six? I suppose it's due to your natural potential."

When Algol, a Three-Digit (Four when sealed), used Demonification (her demon authority), she could casually turn anything—living or not—into a Five-Digit being.

But Ryo could only raise this girl to Seven-Digit status. If he wanted to push her to Six, he'd have to use his own blood.

Still, for a disposable underling, Seven-Digit was perfectly acceptable.

He smiled warmly and said:

"If you can't kill humans, then specialize in killing other demons."

"Oh, right—what's your name?"

The girl looked up, voice filled with reverence and fear.

"Oto."

"Oto, huh?" Ryo grinned. "Good. Go slaughter every demon on this mountain."

At those words, Oto rose to her feet.

She glanced sideways at Rui.

"…Mother…"

That single glance made Rui instinctively step back, eyes filled with panic.

Thankfully, she didn't attack him. She simply vanished, too fast for even an afterimage.

She spared him. For now.

But that wasn't good news.

After all, the only demons on this mountain were Rui's "family"—his siblings and parents. His creations.

And yet, he didn't dare protest. Not even a little.

Those fake family members? He could make new ones anytime.

But his own life? That was irreplaceable.

He didn't want to die.

Ryo, now satisfied with his experiment, said cheerfully:

"Rui, summon Nakime."

Nakime—the Biwa-playing demon who could manipulate space itself.

If Muzan was the brain of the demon race, Nakime was its nervous system.

Her ability let her link to all demons, instantly transporting them into the infinite demon stronghold—Infinity Castle.

Normally, she only used this power when Muzan summoned the Twelve Kizuki.

And while all demons were technically connected to her, only the Kizuki and a few special demons even knew of her existence, much less how to contact her.

As Lower Five of the Twelve Kizuki, Rui had that privilege.

So when Ryo asked, Rui didn't hesitate. He sliced open his wrist, letting his blood spill, and used a secret method to send the message.

It was simple: "Lord Muzan is with me. He commands you to come."

Seconds later—barely even one or two—

A shadowy figure silently materialized beside him.

Ryo's lips curled into a smile.

He had taken the most important step in replacing Muzan Kibutsuji.

He now controlled the entire "nervous network" that connected all demons.

And it was officially in his hands.

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