[FATE] OP Demon King Across Multiverse!

Cú Chulainn crossed his arms, watching Ryuu.

"You know... You really don't fight like a normal human, Master."

Ryuu chuckled. "Didn't I tell you? I'm the Demon King."

Cú Chulainn froze.

"…Demon King? You? Yeah, right! You don't look like one at all, ya bastard!"

Ryuu smirked. "Too late to back out now, Caster."

Cú Chulainn clicked his tongue, realizing—even if he wanted to cancel the contract, he couldn't.

But deep down—he didn't entirely dislike Ryuu as a Master.

"…Fine. Whatever. Let's just end this mess already."

---

Cú Chulainn stretched. "So? Where to next? Archer knows our hideout now."

Ryuu grinned. "We take the initiative. Hunt down the other Servants before they find us."

"…Just the two of us?"

"The others are Blackened, but they're not working together. We have the advantage."

Cú Chulainn scratched his head. "I dunno about this plan, but fine."

---

As they prepared to move, an idea struck Ryuu.

"…If everyone in this world is dead… then Shirou Emiya must be, too."

Cú Chulainn blinked. "Yeah, and?"

"…Which means Avalon should still be intact."

If Artoria obtained Avalon, she would be nearly invincible.

Ryuu clenched his fists. "We need to find it before she does."

"Tch. You and your weird knowledge." Cú Chulainn sighed. "Fine. Let's go."

---

They arrived at the burned remains of Emiya Shirou's house.

Cú Chulainn kicked a piece of rubble. "Master, this place is trashed. What exactly are we looking for?"

"A scabbard."

Cú Chulainn frowned. "Scabbard?"

Ryuu nodded. "King Arthur's ultimate Noble Phantasm—Avalon."

---

Cú Chulainn grumbled but started searching.

Moments later—

"Oi! Is this what you're looking for?!"

Ryuu spun around.

Cú Chulainn held up a golden scabbard, half-buried in the dust.

Ryuu's eyes widened.

"That's it!"

He rushed forward, grabbing Avalon.

A pulse of divine energy radiated from it—this was the real deal.

"Thank god, Saber didn't take it!"

---

Suddenly—Ryuu's instincts screamed danger.

He barely had time to react.

"Berserk Blood – Second Activation!"

In a blur, he swung his sword behind him.

A shadow leaped back, barely avoiding the strike.

Cú Chulainn cursed. "Damn it! It's Assassin!"

Emerging from the shadows, the cloaked figure of Cursed Arm Hassan stepped forward.

"Impressive. You sensed my presence."

"Tch. Looking to steal Avalon?" Ryuu tucked the scabbard into his system storage.

"It does not belong to you." Hassan's voice was cold.

Ryuu raised his sword. "Then come and take it."

...

Hassan's bandages unraveled, black tendrils lunging toward Ryuu.

Before they could touch him—

A wall of wind erupted.

"Hey, asshole! You forgot about me!" Cú Chulainn smirked, stepping between them.

Hassan scoffed. "Foolish Caster."

In a blur, Hassan ripped off his own bandages, revealing his cursed arm.

"Zabaniya – Delusional Heartbeat."

A dark aura surrounded his clawed hand, aimed straight at Ryuu's heart.

Cú Chulainn's eyes widened. "Shit! That's an instant-kill move!"

Ryuu's pupils contracted.

...

Hassan lunged.

His cursed claw dug into Ryuu's chest.

Pain exploded through his body.

"Master!!"

Cú Chulainn roared, summoning his flaming Noble Phantasm.

"Burning Flame Cage – Wicker Man!!"

A massive, flaming giant formed behind him—trapping Hassan in a prison of fire.

Hassan's blackened flesh burned, but he didn't let go of Ryuu.

"You will die with me!!"

With a sickening crack, Hassan squeezed Ryuu's heart.

---

For a moment—Ryuu's vision blacked out.

His body trembled.

Then—

His golden eyes flashed open.

A dark aura erupted from his body—the Seed of the Demon King awakening.

His wounds healed instantly.

Hassan's grip weakened.

"…What? This is impossible."

Cú Chulainn grinned.

"Looks like he's not dead yet, asshole!"

The Wicker Man ignited.

A devastating explosion swallowed Hassan whole.

---

As the flames died down, Hassan's body crumbled into ash.

Cú Chulainn panted. "…Finally dead."

Ryuu stumbled forward, gripping his chest.

He exhaled slowly.

Cú Chulainn laughed. "Oi, Master. Still alive?"

Ryuu grinned. "Takes more than that to kill me."

But in his mind, he knew—

"That... was too close."

He needed more power.

Saber was still out there.

And she wouldn't be this easy.

---

As Ryuu looked at Avalon, safely stored away—

He knew this was just the beginning.

The war wasn't over.

It was only getting started.

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