The Greatest Assassin Gets Reincarnated in Tensura

Arion

High above the Cardinal World, in the ethereal realm of the Heavenly Palace, Veldanava sat upon his grand throne, his golden eyes fixated on the unfolding events below.

For eons, he had watched over existence, a silent observer, rarely finding anything worthy of his direct attention. Even as powerful beings rose and fell, he remained indifferent, knowing none could truly stand in his presence.

But now, something had changed.

Or rather—someone had appeared.

That someone was Arion.

The Demon Who Intrigued a God

Veldanava narrowed his gaze as he observed the demon's actions.

Arion, a demon unlike any other, had not only tamed Veldora, the most uncontrollable of the True Dragons, but had also helped him grow stronger—so much so that Veldora now stood above even his sisters, Velzard and Velgrynd.

Arion had constructed an entire city within minutes, a feat that should have required centuries, bending the laws of creation itself.

Arion had recruited two Primordial Demons into his ranks—beings of unfathomable power that most feared even naming.

Arion was training an army in complete secrecy, not for mere conquest, but for something far greater.

Veldanava leaned forward, resting his chin on his palm, eyes filled with curiosity.

"A demon… doing all this?"

Demons were creatures of chaos, destruction, and self-interest. They fought for dominance, pursued power for their own sake, and rarely worked together unless forced. But Arion was different.

He was not seeking destruction.

He was not flaunting his strength.

Instead, he was building, refining, and shaping his forces like a ruler preparing for something grander than mere war.

The Taming of Veldora

Veldanava's attention flickered toward Veldora.

For countless years, Veldora had been a force of destruction, reckless and wild, never one to listen to reason. Even Velzard and Velgrynd had long given up on trying to guide him.

Yet, here he was—stronger than ever, more disciplined than ever.

Veldora, who once acted purely on impulse, was now growing, evolving.

And it was because of Arion.

Veldanava chuckled softly, shaking his head in amusement.

"You… my storm-bringer of chaos, have been tamed. No chains, no magic—just sheer companionship. How amusing."

The fact that Veldora now surpassed his sisters was proof enough that Arion was no ordinary demon.

A City Built in Moments

His gaze returned to Arion's Eternal City—a place that should not exist.

A city forged in mere minutes.

A city that radiated power and mystery.

A city built not for conquest, but for something much deeper.

Veldanava saw how Arion recruited demons not as pawns, but as warriors, infiltrators, and rulers.

The Black Legion, led by Diablo, was trained in the art of absolute destruction and domination.

The White Legion, led by Testarossa, specialized in control, subterfuge, and ruling from the shadows.

Every member of his forces was undergoing rigorous training—not just in combat, but in deception, governance, and even human nature.

"A demon… training others to act like humans, to blend in, to infiltrate?"

Demons typically had no need for such tactics. They were beings of raw power, feared wherever they went.

But Arion was thinking beyond brute force.

He was crafting an empire from the darkness.

A Decision in Silence

Veldanava remained silent for a long moment, deep in thought.

Finally, he spoke to no one in particular.

"I will meet him."

But not now.

Arion was still growing, evolving, carving his own path. If he interfered now, it would disrupt the natural course of his rise.

But when the time was right—**when Arion had ascended to the peak of his power—**Veldanava would descend from the heavens and stand before him.

Not as a god.

Not as an omnipotent creator.

But as a warrior seeking a worthy opponent.

A faint smirk played on Veldanava's lips, a rare flicker of excitement filling his golden eyes.

"Perhaps… he will be the one to finally make me fight seriously."

For now, he would watch.

But soon, Arion would stand before the Supreme Dragon himself.

Years of Secrecy, an Army in the Shadows

The Jura Forest, once known for its endless wilderness and untamed magic, had become the unseen stronghold of Arion's growing empire. Years had passed, and under his guidance, an entire army of demons had been forged in secret. No nation, no king, were aware of the vast network of spies, infiltrators, and warriors Arion had planted across the world.

Each demon in his Black and White Legions had a role—some acted as merchants, others as nobles, even a select few had woven their way into royal courts, whispering advice into the ears of rulers who never once suspected the demonic presence within their walls.

And all of it, every move, every shift in power, every rumor of war—was reported directly to Arion.

No one knew about the Eternal City hidden deep in Jura Forest. No one suspected that a hidden demon army was growing stronger by the day.

No one—except Veldora.

Though Veldora remained as carefree and reckless as ever, he had changed.

He had grown.

He had become stronger.

He still traveled the world, causing chaos in his wake, but unlike before, there was now a control, a refinement to his destruction. He no longer rampaged mindlessly—he was learning.

Yet, he was still Veldora.

Which meant, every once in a while, he still did something stupid.

It happened on one of his usual "adventure outings."

Veldora had been soaring across the lands, enjoying his newfound strength, flexing his power just for fun. He wanted to see how much stronger he had become, to test the limits of his newly trained body.

And then—it happened.

A stray Dragon Breath attack, unleashed without much thought, obliterated a small village below.

Veldora winced. He immediately realized his mistake.

"Ah… that wasn't supposed to happen."

The village was gone.

He scratched the back of his head, glancing around.

"Ehh… maybe no one saw?"

He knew that was wishful thinking.

And just as he was about to fly off like nothing had happened—

A cold, terrifying aura filled the sky.

The temperature plummeted.

The very air froze.

The clouds above turned white as frost spread through the sky itself.

A voice, filled with pure authority, rang out like a crashing avalanche.

"VELDORA! WHAT DID YOU DO?!"

A chill went down his spine.

He slowly turned his head.

There, descending from the heavens with an aura of absolute frost, was Velzard.

Her blue-silver hair flowed like a frozen waterfall, her diamond-like eyes gleamed with icy fury, and her wings spread wide, radiating a freezing storm that made even the ruins below start to crystallize in frost.

She landed before him, arms crossed, her presence making the very air tremble.

Veldora groaned.

"Of all the people who could've shown up…"

The Clash of Siblings

Velzard took one look at the burning, ruined village and then back at Veldora.

Her eyes narrowed.

"He's still the same reckless idiot…"

"Explain. Now."

Veldora sighed and crossed his arms, still hovering lazily in the sky.

"Look, Sis, it was a mistake. I didn't mean to—"

"A mistake?" Velzard's voice turned sharp. "A mistake? You burned down an entire village, Veldora! I have tolerated your stupidity long enough. You need to be educated!"

Veldora immediately held up his hands. "Wait, wait, wait—let's not get crazy here! I'm telling the truth, I didn't mean to destroy it!"

Velzard's eyes flashed.

"No excuses!"

Before Veldora could react, she shot forward, moving at speeds even he barely registered.

Her fist, coated in ice and raw dragon power, surged toward his face.

In the past, Veldora wouldn't have even thought to dodge.

But this time—his body moved on instinct.

With a swift, effortless motion, he tilted his head back, letting the punch miss by mere inches.

The shockwave alone shattered the ground below.

Velzard's eyes widened in pure shock.

He dodged?

Before she could process it, Veldora spun in the air and descended, landing gracefully on the ground.

Then, something even more shocking happened.

In a flash of golden lightning, Veldora's massive dragon form dissolved.

And in his place stood a man.

Velzard froze.

Her entire body stiffened.

Her breath hitched.

For the first time in her entire existence—she was seeing Veldora in his human form.

And he looked… different.

He was tall, his golden hair wild, his eyes sharp, filled with an intensity she had never seen in him before. He wore a regal black coat with golden patterns, and his very presence radiated an overwhelming force.

Velzard felt an unfamiliar sensation—disbelief.

"…You… you have a human form?"

Veldora grinned.

His usual carefree smirk was still there, but it was different now—sharper, more confident.

"Yeah, cool, right? I figured it out a while back." He flexed his fingers, rolling his shoulders as if testing his body. "Gotta say, being in this form makes movement a lot smoother."

Velzard couldn't respond for a moment.

The Veldora she knew was wild, uncontrollable, childish.

But this Veldora standing before her… was different.

More refined.

More composed.

More… powerful.

She clenched her fists, struggling to find words.

Finally, she spoke, her voice quieter—but filled with determination.

"…Have you really grown stronger?"

Veldora tilted his head.

Then, he grinned.

"Why don't you find out?"

For the first time in their existence, Velzard realized something.

Her reckless, foolish little brother—

—Might actually surpass her.