The Greatest Assassin Gets Reincarnated in Tensura

Under the cover of the moonless night, the MC prowled the enemy fortress like a specter of death. His form blended into the darkness, slipping through unseen cracks in the world itself. Every step, every breath—calculated. Silent. Lethal.

Callas and his army had holed themselves up in an abandoned fortress, its walls weathered by time but still standing strong. Watchtowers overlooked the entrance, archers posted at every vantage point, and squads of soldiers patrolled in synchronized formations.

A formidable defense? Perhaps.

But against him—they might as well have been children playing war.

Using Shadow Steps, he infiltrated the fortress undetected, slithering through corridors, halls, and open courtyards. His Eavesdropper's Veil allowed him to hear the hushed whispers of Callas' men.

"The King must be desperate if he hasn't tried attacking us yet."

"Callas is smarter than him. He has plans beyond this war."

"I heard he's already making deals with other nations."

"We're taking the kingdom. Soon."

The MC smirked. Not if I end you first.

His first target was Jorik, a trusted officer in Callas' army, one who had the authority to approach the general without suspicion.

Like a phantom, he appeared behind Jorik, a cold hand clamping over his mouth before he could react.

"Sleep."

Jorik collapsed instantly, his mind and body now under the MC's control.

Through Jorik, he lured Callas into an isolated chamber, away from his army.

Jorik (under the MC's control): "General, there's something urgent—news from our spies in the capital. We should speak alone."

Callas, ever the strategist, narrowed his eyes.

"Fine. But this better not be a waste of my time."

Hook. Line. Sinker.

The moment Callas entered the chamber, the door slammed shut behind him.

The shadows in the room seemed to move, twisting unnaturally—and from them, the MC emerged.

Callas' instincts flared, his hand darting to his sword—too slow.

"Kneel."

Callas' body locked up, his knees slamming to the floor. His eyes widened in terror as an unseen force crushed his will, rendering him powerless.

"W-What are you…?" he choked out, veins bulging as he fought against the overwhelming force.

The MC crouched beside him, a cold smirk playing on his lips.

"The one who decides your fate."

His fingers brushed Callas' forehead, and with a pulse of dark energy, the general's mind was laid bare.

Every secret.

Every plan for war.

Every deal with foreign nations.

Every hidden supply route and battle strategy.

The MC took it all.

When he was done, he released Callas from his grasp.

The general gasped for air, shaking violently, his body drenched in sweat.

He tried to speak—tried to resist—but his fate had already been sealed.

"Shadow Requiem."

Dark tendrils surged from the MC's fingertips, consuming Callas whole. The general's body erased from existence, his very soul dragged into the abyss.

One down. Now, for the rest.

The MC melted back into the shadows, weaving through the fortress like a wraith of death.

One by one, the officers fell.

A captain stood on the battlements, overseeing the patrols. The MC appeared behind him, a single dagger piercing his throat.

Two commanders discussed war plans in the strategy hall. He strangled them with shadows before they could scream.

A group of elite knights shared drinks in the barracks, celebrating their soon-to-be victory. He poisoned their wine with an undetectable curse—one that made their bodies rot from the inside out.

As the higher-ranking officers fell, the fortress descended into chaos.

Men shouted.

"We're under attack!"

"Who is it?! The King's forces?!"

"No... something else. Something unseen!"

Fear spread like wildfire.

The MC activated one of his strongest technique—"Umbral Cataclysm."

The shadows of the fortress came alive.

Darkness crawled up the walls, slithered through the halls, and consumed every soldier it touched.

Swordsmen screamed as their own shadows impaled them.

Archers on the towers were dragged into the abyss, never to be seen again.

A battalion tried to flee through the gates—only to find them sealed shut, as an unseen force suffocated them in the dark.

Not a single soul escaped.

By dawn, the fortress stood empty. Silent. Lifeless.

The bodies had vanished, devoured by the abyss. The only trace left was the lingering scent of death and despair.

The MC stood at the castle gates, gazing at his completed work.

His first true act of war.

Now, it was time to claim his reward.

With a satisfied smirk, he stepped into the shadows—and disappeared.