[FATE] OP Demon King Across Multiverse!

"I see, Master. Is that truly what you believe?"

"Of course. It is precisely because you 'do not understand people's hearts' that your knights followed you with such unwavering devotion."

Hearing Ryuu's words, Artoria's eyes gleamed with newfound determination. She looked at him with gratitude.

"Thank you, Master. I am… fine now."

Ryuu nodded in approval.

Keeping her as Blue Saber isn't so bad after all.

But just as they continued walking, a surge of magical energy abruptly blocked their path.

A towering, three-meter-tall warrior emerged before them, his dark skin gleaming, golden waist armor reflecting the light.

Behind him stood a young man, likely his Master.

The sight of the Servant's distinctive golden pupils and Persian-style armor made Ryuu's eyes widen.

"No way… Darius III?"

---

Artoria immediately stepped forward, ready for battle.

"Master, be cautious! This Servant is formidable—we must not underestimate him!"

She moved to draw Excalibur, but Ryuu raised a hand, stopping her.

They were in a public area.

A battle here could cause massive collateral damage.

Although Ryuu didn't particularly care about civilian casualties, avoiding unnecessary trouble was just common sense.

On the other side, the opposing Master seemed to hold the same idea.

Neither side made the first move.

---

"Rider-class Servant. True Name: Darius III of Persia."

Ryuu muttered the name aloud, analyzing the Servant before him.

"The Persian king who opposed Iskandar… but why Rider?"

Darius was normally summoned as a Berserker, his mind lost to madness.

Yet here he was—standing tall, composed, and entirely sane.

Something was wrong.

This wasn't the Holy Grail War Ryuu remembered.

---

"Oh? I thought I was the first to summon a Servant. Looks like someone beat me to it."

The young Master finally spoke, his voice tinged with arrogance.

Ryuu quickly assessed him.

Young, student-aged.

Weak magical presence.

Clearly inexperienced.

A novice Magus.

That meant—an easy kill.

---

Ryuu smirked.

"You're pretty bold. A weakling like you, talking as if you matter?"

The student flinched, but quickly tried to regain his composure.

"Hah! Don't think you can act superior just because you summoned Saber! You have no idea who will win this war!"

Ryuu laughed.

"I don't care if Rider is strong. If I kill you first, it won't matter."

The opposing Master visibly paled, instinctively taking a step back behind Darius III.

"Tch! Don't get cocky! My Rider is invincible! But there are too many people around today, so I'll let you go—for now!"

With that, the student turned on his heel and left, Darius following close behind.

Ryuu watched them disappear into the crowd.

"Interesting. Looks like the first casualty of this Holy Grail War has already been decided."

---

As they continued walking, Artoria's expression darkened.

"Master, there is something I must make clear."

Ryuu raised an eyebrow.

"You only need to support me from behind. Leave the fighting to me!"

Ryuu's smirk widened.

"Sorry, but I can't do that."

Artoria's face fell.

For a brief moment, the memory of Emiya Kiritsugu flashed through her mind.

But then Ryuu spoke again—

And his next words completely shattered her comparison.

"A Servant is a warrior. A Master is a leader. But I am the Demon King."

"How could I ever cower behind you?"

---

Artoria was stunned.

"Master, you—"

Ryuu's golden pupils gleamed with an unmistakable challenge.

"Saber, let's fight."

Artoria froze.

"You… want to duel?"

"I need to know my limits. I need to see where I stand against a Servant."

Artoria hesitated.

In her experience, humans could never match Servants in direct combat.

But…

Ryuu wasn't just a human.

His golden pupils burned, radiating power and confidence.

There was no refusal.

A Demon King's challenge could not be ignored.

Artoria gripped Excalibur.

"Very well, Master. I, Artoria Pendragon, accept your challenge!"

---

They returned to Ryuu's temporary training ground, an isolated open space far from the city.

Artoria summoned her armor, standing in her full Knight of the Round Table regalia.

She raised her sword—yet to be revealed.

Ryuu immediately recognized the phenomenon.

"Wind King Barrier.* It completely conceals Excalibur's appearance and length.**"*

Artoria's stance remained firm.

"Master, are you ready?"

Ryuu twirled Wrath in his hands, a grin forming.

"Come at me, Saber. Show me the strength of the King of Knights!"

---

Without hesitation, Ryuu lunged first.

His blade struck forward, aiming straight for Artoria's heart.

CLANG!

Excalibur deflected the attack, the force of Wind King Barrier sending shockwaves outward.

The aftershock tore through the air, slicing into Ryuu's skin.

"Tch. As expected, I can't break through with normal attacks."

His eyes flashed gold.

"Berserk Blood—Second Activation."

---

Draconic scales surfaced on Ryuu's arms, his strength instantly amplifying.

He leaped into the air, bringing Wrath down in a devastating vertical slash.

Artoria, momentarily caught off guard, raised her blade just in time to block.

But—

The force of the impact sent her stumbling backward.

---

"Not bad, Master."

Artoria steadied herself.

Then—she counterattacked.

Excalibur flashed—

Ryuu's Observation Haki kicked in, predicting the trajectory of her strike.

He dodged—barely.

Yet, he was still forced back, unable to counter.

"Even with all my buffs, I'm still losing in raw speed and strength…"

His grip on Wrath tightened.

"Fine then—Third Activation!"

---

With his third Berserk Blood activation, Ryuu's movements sharpened.

This time—he fought back.

He parried Artoria's attacks, launching quick counters whenever he saw an opening.

Yet, in the end—

He was still being pushed back.

"Shit. Even with my full strength, I can barely keep up…"

But—he wasn't finished yet.

---

"Word Spirit: Hellflame!"

A massive wave of black fire erupted from Ryuu's position, surging toward Artoria.

Seeing the attack's power, Artoria didn't hesitate.

"Wind King Hammer!"

With a single slash, she unleashed the barrier's compressed wind—

The fire and wind clashed—

BOOOOM!

A massive explosion erupted, shaking the battlefield.

A tornado of flames shot into the sky, visible for miles.

As the dust settled—

The battle had only just begun.

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