The Greatest Assassin Gets Reincarnated in Tensura

In the heart of the High Human Kingdom, within the grand citadel of Zerath'Kaal, where spires of obsidian pierced the storm-darkened sky, an unholy ritual was in motion. Deep beneath the towering fortress, where the air was thick with the metallic scent of blood and burning incense, Jahil, the supreme ruler of the High Humans, stood atop a raised platform, his piercing gaze fixed upon the massive summoning circle etched into the stone floor.

Faint whispers of the abyss curled through the chamber like spectral tendrils, drawn toward the arcane sigils pulsating with dark energy. This was a ritual unlike any before—a summoning that demanded a horrific price, one that would shake the very fabric of reality.

Above, in the dimly lit war chamber, Jahil sat upon his onyx throne, drumming his fingers against the armrest, his eyes shadowed with growing impatience. Before him, his highest-ranking generals stood rigid, their expressions a mix of duty and silent dread. Torches flickered, casting grotesque shadows upon the ancient stone walls lined with banners of the High Human Empire.

Jahil's voice, cold and sharp as a dagger, cut through the thick air.

"What is the status of the preparations?"

The room tensed. General Varkas, a battle-hardened veteran with cruel eyes and a scar running across his jaw, stepped forward. He was known for his ruthless efficiency, a man who saw morality as an obstacle, not a virtue.

"We are close, my lord," Varkas replied, his tone unwavering. "But we require more… sacrifices."

Jahil's gaze darkened. "How many more?"

"At least five hundred."

The ruler exhaled slowly, his patience thinning. He turned his gaze to General Halvar, the one responsible for the kingdom's internal affairs—the one tasked with procuring these so-called sacrifices.

"And what excuse have you conjured this time?" Jahil's lips curled into a smirk, mockingly.

Halvar bowed slightly, unfazed by the derision. "Criminals, prisoners of war, and dissenters have already been rounded up. But… it is not enough. We have begun raiding outlying villages. The populace believes we are hunting traitors."

Jahil's smirk widened. "Good. Let them believe what they wish. They will serve the empire, one way or another."

Below the castle, the streets of Zerath'Kaal were filled with the echoes of iron-shod boots. Soldiers moved like hunting dogs, dragging terrified villagers from their homes, shoving them into iron-wrought cages mounted on wagons. Children screamed for their parents, wives clung to their husbands, only to be ripped away.

The soldiers, ruthless and efficient, paid no heed to the pleas.

"Move! The King demands it!" barked one of the captains. "Resist, and you'll be flayed instead of sacrificed!"

Some villagers, realizing the fate that awaited them, tried to run. The air was soon filled with the sounds of whips cracking and blades slicing flesh.

A young woman fell to her knees, sobbing, clutching a child. A soldier yanked the child away, tossing the screaming boy into the cage. The mother lunged after him—only for a sword to pierce her back.

The soldier wiped the blood off his blade and muttered, "Too much trouble."

The carts, filled with hundreds of condemned souls, rumbled toward the citadel, where the abyss itself awaited.

Back in the underground ritual chamber, the sacrifices were lined up in chains, trembling, eyes wide with terror as they beheld the monstrosity of the summoning circle before them. The symbols engraved upon the floor pulsed like a living thing, whispering in a language not meant for mortal ears.

At the head of the ritual stood the High Priest of the Black Sun, an emaciated figure adorned in ceremonial robes woven with abyssal glyphs. His voice, dry and ancient, slithered through the chamber.

"The blood price must be paid."

One by one, the prisoners were dragged forward. Blades kissed throats, crimson rivers flowed, and the sigils drank deeply.

Jahil watched in silence, his expression unreadable. Behind him, his generals stole uneasy glances at each other. They had witnessed dark rituals before, but this… this was different. The sheer magnitude of suffering, the sheer depth of the abyss they were calling upon—it unsettled even them.

And then—the chamber trembled.

The blood on the floor began to move, twisting, crawling toward the center of the summoning circle like a living creature.

The darkness deepened, swallowing the torchlight, as an inhuman growl rumbled from beyond the veil of existence.

A voice—ancient, abyssal, filled with malice beyond comprehension—rippled through the chamber.

"Who… dares… call me forth?"

Jahil stepped forward, a sinister grin spreading across his face.

"I am Jahil, ruler of this kingdom, and I offer you blood, power, and servitude. Now… rise, and serve me."

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In the endless abyss of the Underworld, where darkness stretched without limit and the sky burned in an eternal crimson inferno, only one law reigned—power above all. It was a world of constant bloodshed, a battlefield where demons clashed without pause, struggling for dominance.

Yet, despite the countless battles, one being stood at the apex.

Rouge, the Primordial of Wrath.

He was not merely a demon—he was carnage incarnate, a walking calamity whose presence alone commanded absolute submission. His scarlet hair cascaded down his broad shoulders, flowing like rivers of blood. His piercing crimson eyes burned with an unrelenting hunger, as if always searching for his next conquest. Draped in a regal crimson coat, embroidered with black infernal symbols, his very stance radiated the dominance of a king who had never once been dethroned.

But most terrifying of all was the aura that surrounded him—a sea of hellfire, hotter than the core of a dying star, rippling with power that could incinerate lesser beings upon mere proximity.

And yet… he was bored.

Rouge sat upon his throne of charred obsidian, perched atop a colossal fortress forged from the bones of fallen challengers. The structure itself pulsed with power, as if the souls of the defeated still screamed within its walls. Below, in the vast hellish coliseum, thousands of demons fought in a perpetual struggle for survival.

The sound of clashing claws, tearing flesh, and agonized wails filled the air—a symphony of carnage.

Rouge barely paid it any mind.

Once, he had relished these battles. Now, they were nothing but predictable affairs, mere entertainment for lesser demons. No one strong enough dared to step forward.

And the one who had always matched him in power and fury… was gone.

For as long as he could remember, there had been only one demon who had stood on equal footing with him—Noir, the Primordial of Darkness.

Their battles had been legendary, their clashes reshaping the very foundation of the Underworld. Entire legions had been obliterated just from the aftershocks of their fights. The flames of Rouge and the abyss of Noir had intertwined in endless combat, neither willing to yield, neither willing to fall.

But now… Noir was missing.

Not dead. No, if Noir had fallen, Rouge would have felt it in the very fabric of existence. But he had simply vanished from the Underworld.

Some whispered that Noir had gone to the Material World. Others claimed he had taken an interest in the affairs of the living.

Rouge scoffed at the very thought.

"What could possibly be worth his time up there?"

It made no sense.

The Material World was a playground for lesser beings. What interest would Noir have in it? And more importantly… why had he abandoned their rivalry?

The question gnawed at Rouge like an itch he could not scratch.

Without Noir, the Underworld had lost its only real challenge.

The other Primordials? They had power, yes, but none of them presented a real challenge.

Rouge leaned forward, resting his elbow on his knee, his clawed fingers tapping against his cheek. His flames crackled, mirroring his growing impatience.

Noir was gone. There was no one left to challenge him.

If Noir had left for the Material World, then perhaps there was something worth seeing there after all.

But as Rouge brooded over his next move, two other Primordials had already set their sights on him.

Primordial Bleu and Primordial Vert had always been cautious when it came to Rouge. His raw power and unyielding dominance were undeniable, but he was predictable.

Bleu, was sharp, calm, and impossibly laid-back. She preferred to watch, analyze, and play the long game. While the others clashed in battle, she always found a way to get what she wanted without lifting a finger.

Vert, on the other hand, was reckless, wild, and impulsive—a chaotic force of nature who relied on instinct and sheer destruction. She had an almost childish excitement when it came to battle, but that made her unpredictable, dangerous.

Together, they had an idea.

Rouge had ruled for far too long. With Noir gone, the balance was shifting. If they worked together, they could take him down.

One day, Bleu arrived at Vert's territory—a sprawling fortress of chaos and destruction. Unlike Rouge's structured rule, Vert's land was pure madness. Demonic creatures ran wild, smashing things for no reason, laughing maniacally.

Bleu sighed, stretching her arms over her head as she flew down lazily.

"Every time I visit, this place looks worse," she muttered to herself.

The moment Vert's guards spotted Bleu, alarms blared—a mix of screams, explosions, and what sounded like someone playing the trumpet horribly.

"IT'S THE PRIMORDIAL BLEU! SUMMON THE MISTRESS!"

Inside the castle, Vert was in the middle of a game—playing with one of her demon pets, throwing it into a pit and seeing how fast it could climb out.

When one of her servants rushed in, yelling about Bleu's arrival, Vert immediately jumped up, grinning.

"Ohhh? Bleu's here? She wants to fight?! Finally! I was getting soooo bored!"

Without a second thought, she shot out of the castle, blasting through a wall instead of using the door.

Vert landed with a loud crash, kicking up dust as she cracked her knuckles.

Her gold-green eyes gleaming with anticipation.

"So you're here for a fight? Ready to get your butt kicked?" she grinned, hopping from foot to foot like an eager child.

Bleu, who had just touched down, stretched her arms again, yawning.

"Wow. That's your first thought?" she sighed. "Vert, not everything has to be a fight, you know."

Vert froze mid-hop, looking genuinely confused.

"…It doesn't?"

Bleu shook her head, chuckling.

"No. Sometimes, smart people talk first."

Vert blinked, then pouted.

"Boooooring."

Bleu ignored her, casually adjusting her long, flowing robes.

"Listen, I actually came with a better idea. Something fun. Something big."

Vert perked up at that. "Big?"

Bleu's lips curled into a smirk.

"Yeah. You and me. We take down Rouge."

Vert's wings flared as she let out a wild, excited laugh.

"Oooohhh! Now that sounds fun!" she beamed. Then, a second later, she paused. "…Wait. Rouge is really strong."

Bleu nodded.

"Yep."

Vert tapped her chin, thinking.

"…And he could probably kill us both."

Bleu nodded again.

"Definitely."

Vert gasped dramatically.

"Wait. Am I the distraction?!"

Bleu laughed. "No, no. We're in this together."

Vert looked suspicious. "Mmm… you're really sneaky."

Bleu shrugged. "I prefer the word 'clever.'"

Vert grinned again. "Hehe. I like it. Okay, let's do it! What's the plan?"

Bleu's eyes gleamed as she leaned in.

"Oh, Vert. You're gonna love this."

And so, the two most unpredictable demons in the Underworld set their sights on the strongest.

Rouge had no idea what was coming.