Imperium of Man Terra Aeterna Season 01: Rise of Humanity's War Machin

Three Days Later, Nighttime

Northern Japanese Archipelago, Off the Coast of Sasebo Port

A black heavy cruiser sliced silently through the dark ocean, its steel hull gliding like a shadow beneath the moonless sky.

Its shell was painted in shades of black and crimson, equipped with eight primary 203mm caliber guns, and topped with a double-layered conning tower—each detail unmistakably marking it as a Prinz Eugen-class heavy cruiser.

Under the cover of night, the warship moved with near-total silence—not a single ordinary human noticed its presence.

Reuel stood atop the command bridge, his gaze fixed on the faint outline of land in the distance.

"Commander, are you sure Muzan will come?"

Beside him, Prinz Eugen—long silver hair and a crimson streak on her forehead—posed the question in her usual calm but razor-sharp tone.

"Yes. And he'll use every means at his disposal to seize my Aobanagiku... that doesn't even exist."

Reuel didn't avert his eyes. He knew Muzan far too well—well enough to understand the insanity of the Demon King's obsession with eternal life.

According to the leaked script released to the public, today was the day a "wealthy entrepreneur" had allegedly discovered the blue Aobanagiku and was preparing to return home. Local newspapers—whether intentionally or not—had leaked the man's travel route. Coincidentally, his point of departure was Sasebo Port, now eerily empty.

To Muzan, this was a golden opportunity. There was no reason to let it pass.

"And what if he doesn't show? What if he decides to hide and wait?"

This time, it was Taihou who spoke—her suspicion toward the entire operation had lingered since the beginning.

In her mind, the commander seemed to be baiting a shark with a threadbare net.

But what she couldn't determine was whether the beast would actually take the bait.

"Then we'll topple the Shogunate first, seize every resource to build a Gundam, and blow Muzan and all of Japan into the sky with a single shot."

Reuel gave a faint smirk.

Of course, he had prepared numerous backup plans. But for now, he wanted to try the simplest approach—deceive Muzan and the Twelve Kizuki, then annihilate them all at once.

And maybe, have a little fun doing it.

An amusing thought crossed his mind.

"Oh..."

The shipgirls nodded silently and moved to prepare for battle.

Taihou and Hornet stood on the deck of the Prinz Eugen. Since the shallow waters around Sasebo Port couldn't accommodate an aircraft carrier's full hull, they had chosen to fight in their humanoid warship forms.

Both raised their hands. Several carrier-based fighter planes launched, flying against the wind toward the distant shore.

"Target sighted!"

A scout plane's message soon came through:

"Thirty-five kilometers northwest—detected a large, fast-moving cluster heading toward the coast!"

On land—

Swish. Swish.

Countless dark shadows rushed through the forest, barely visible to the human eye.

Some crawled like reptiles, limbs touching the ground. Others leaped tree to tree like monstrous primates.

Upon closer inspection, one thing was clear: they were all Oni—demons of grotesque and terrifying forms.

There were Oni with dozens of arms, their limbs wrapped like serpents around their torsos. There was a swamp-dwelling Oni dressed like a ninja. A bow-wielding Oni. And of course, hordes of low-ranking demons trailing behind.

Leading them all was the progenitor of all demons himself.

Growling and howling, the Oni swarmed toward the shoreline.

One hundred demons moving through the night.

Nearly the entire demon force of Japan had converged in one place.

From that monstrous horde came eerie sounds—rubbing, hissing, low snarls—like a symphony composed in hell.

At the rear of the procession stood a pale-faced young man.

Muzan Kibutsuji—King of the Oni.

His form was hidden, but his senses were sharp.

He knew the conditions well: no humans around, and not a trace of the Demon Slayer Corps.

Initially, after the sudden, inexplicable death of Doma, Muzan had considered retreating from the hunt.

But decades of failure—and his insatiable thirst for eternal life—pushed him to take one final risk.

If he succeeded… the sun would never be his enemy again.

He would become truly immortal—perfect and eternal.

"Strange… Where is the Demon Slayer Corps?"

At the front of the formation stood two figures.

One was pale-skinned, with short pink hair, black markings across his face, and the number "Three" carved into his eyes.

The other had an elongated face and six eyes—each bearing inscriptions of rank.

In his primary pair, the markings were clear:

"Upper Moon" and "—"

They scanned the area—no humans in sight. No businessman. No slayers.

Of course, they weren't alarmed.

They were Upper Rank demons. Most Demon Slayers were mere prey to them.

And with hundreds of Oni at their side, they could erase an entire city if they wished.

"What kind of idiot from the Demon Slayers would dare face all of us at once?"

None of them believed it was a trap.

Yet Muzan remained silent.

With a single wave of his hand, the Oni horde scattered, their sharpened senses sweeping the surroundings—far beyond human capability.

Before long, they saw it.

A warship, anchored in the distance.

Large. Unfamiliar.

Not a Japanese Navy vessel.

Even Muzan felt a strange unease as he laid eyes upon the cruiser.

Its shape, its color—even the flag it bore—none of it belonged to this era.

"That… what is that…?"

Muzan furrowed his brow as he stared at the vessel, a single disturbing thought beginning to whisper in the back of his mind:

"Have I… truly been deceived?"

On the bridge of the Prinz Eugen, Reuel stood tall, gripping a telescope, squinting as he observed the land stretching out in the distance.

It started out as a random idea—just bait to lure Muzan out of his den.

But reality far exceeded expectation.

Muzan actually came. And not alone—he brought his entire Oni family and army, ready to fight to the death for something that might not even exist.

The blue Aobanagiku flower.

Something he craved so desperately, as if it could somehow save his life already drowning in emptiness.

"Ten... a hundred... seven hundred..." Reuel murmured quietly, counting the blips filling the radar.

"Commander, don't tell me you actually stabbed the Demon King right in his own lair," Taihou groaned, eyeing the radar interface with a tense expression. Massive red blips filled the screen.

Their radar was originally designed to detect enemy aircraft and warships, not small targets moving in irregular patterns.

But Muzan's Oni were no ordinary creatures.

Some appeared semi-transparent, some pitch black and blindingly bright. Others... were strange enough that the scanning system didn't know whether to classify them as human, animal, or inanimate object.

They were simply marked as: unidentified entities.

"At the very least, it saves us time and energy. We don't have to comb through the entire mainland to find them," Reuel said, coughing lightly.

He lowered his telescope.

"Open fire. Free fire."

At once, his grin turned into something ridiculous.

"Remember, this isn't Russia... eh, I mean, not Japan?"

Taihou simply sighed—sarcasm in the middle of an all-out war was Reuel's specialty.

---

Coastal Side

The Oni forces swept across the land with brutal force. The aura of death followed their every step.

Muzan stood far behind, silent and alert. He was convinced Reuel's lie was truth.

According to all investigations—both open and clandestine—the blue Aobanagiku flower had indeed been found. The target was here.

Today, they had to be intercepted. And killed.

But what awaited them was... emptiness.

There wasn't a single human being. Even the fishermen from surrounding villages seemed to have been evacuated long ago. Even more suspicious, the Demon Slayer Corps were nowhere to be seen.

Deploying Oni forces at this scale should have attracted their attention by now.

Muzan narrowed his eyes.

"Could it be...

A trap? Or did I miscalculate something...?"

He retreated into the forest's shadows, ordering his subordinates to scout ahead. His instincts began to scream.

And just then—

BUZZZZZZ—!

The sky trembled.

"Air strike incoming!"

"Air strike ready," came a female voice with a cold, threatening British accent.

Over three hundred dive bombers and torpedo planes emerged from behind the clouds above the open sea. Each one came bearing destruction.

SBD Dauntless. SB2C Helldiver. Junkers Ju 87 Stuka.

Classic World War II aircraft roared into formation.

With impossible speed and maneuvers no ordinary technology could achieve, they came in low like a flock of death eagles.

Thanks to the mind-cube–based military system, the shipgirls were now able to construct any type of aircraft without faction or camp limitations.

Unfortunately, they still couldn't form starfighter units since their main bodies were carrier-based ships.

But for Oni... this was more than enough.

The screeches of dive bombers ripped through the air. The sound of their engines formed a symphony of horror never before heard by creatures of the dark.

The Oni forces panicked. Even the strongest among them froze momentarily—what flew above wasn't beast or human, but machines from hell born of another world.

BOOM—BOOM!

The Obi-Oni sneaking ahead didn't even get to react.

High-powered aerial bombs smashed into them from low altitude.

Hei Shimo—an Oni with Moon Breathing techniques, strong enough to withstand a Sun Blade—was instantly blown to pieces by a single direct hit.

Oni bodies could regenerate. But not if they were disintegrated down to the molecular level.

The air strike was carried out in a carpet pattern. The shockwaves alone were enough to vaporize lower-level Oni. What remained... were only scorched silhouettes.

Super-saturation attacks were unleashed mercilessly. The shipgirls lacked neither ammunition nor firepower—Minato harbor's industry had reached an absurd level. Energy, materials, and cost were not a concern.

BOOM—BOOM—BOOM!

The first wave of explosions turned several kilometers of land into a blazing inferno.

Torpedo planes followed from behind, launching anti-ship projectiles strong enough to pierce the armor of a battleship.

Their targets: Oni who had survived the first wave.

Not a single living being could endure it.

Once a torpedo hit, even the toughest Oni body would be reduced to nameless dust.

SWISH—SWISH!

Final wave. The explosions reflected off the sea surface, illuminating the night sky with a terrifying blue-orange glow... beautiful in a horrifying way.

When it was all over, all that remained was the sound of burning fire and the distant drone of retreating engines.

Most of the Oni... had been annihilated.

Muzan Encircled

"Muzan, don't let him escape," said Reuel, his voice flat but heavy with meaning.

"Commander, relax," replied Taisho, a thin smile curling on his lips. "If he were hiding, maybe it would take some effort to find him..."

He then fixed a sharp gaze on the radar.

"...But since he dared to show his face, and is now surrounded from all directions—then, there's absolutely no chance of escape, is there?"

Taisho synced the scout planes' coordinates to the radar interface. A large red dot began moving quickly, away from the center of the map.

"Target's on the move. Fast," he muttered.

Several high-altitude scout planes immediately locked onto the target's position. Thermal cameras and tracking systems confirmed the identity: Kibutsuji Muzan.

"Oh, he's really running..." Reuel clicked his tongue. "Fitting for someone titled the Demon King."

He glanced at the radar scale. Based on rough calculations, Muzan's running speed was approaching subsonic levels.

"Even the fastest train in the world wouldn't be able to catch him..." he said, half admiring, half amused. "That kind of speed... a bit beyond reason."

But then he turned to Richelieu. "Still slower than a shipgirl's artillery shell, right?"

Richelieu simply smiled calmly. She had already rotated her main body, aligning the ship's main guns.

Locked on.

Tracking the red dot's movement on the radar.

Adjusting for elevation and wind speed.

BOOM—BOOM—BOOM!!

Several heavy rounds were fired in unison. The muzzle flash lit up the night sky. In seconds, off in the distance, mushroom clouds began to rise from the forest.

Explosion after explosion rocked the ground, igniting massive fires that danced among the trees.

---

Muzan's Reaction

Fear. Regret. Confusion.

It was hard to imagine what kind of expression was carved into Muzan's face as he was hit by a brutal carpet bombing.

Even a thousand years ago, when his body was destroyed over and over again by Yoriichi Tsugikuni, the fear he felt wasn't this intense.

Sun Breathing was an extraordinary art. But still within the realm of his understanding.

What was happening now... was not.

He didn't know what a dive bomber was, or a torpedo plane.

Didn't understand what kind of bomb could produce explosions this powerful.

The bombs being dropped—dozens of times stronger than any explosive ever created by man.

The ghosts that had been following him earlier—vanished in an instant, turned to dust without a trace.

If not for his near-perfect reflexes and hyper-responsive movement, he himself would have been obliterated like them.

"Humans… is this some new weapon from the Demon Slayers...?" he thought, gritting his teeth.

"...No, impossible. They've never had this kind of technology..."

---

The Escape

Without wasting a second, immediately after the first wave of bombardment hit, Muzan bolted.

He left all his subordinates behind without hesitation, tearing through forests and valleys, running wildly toward what he considered a safe place.

He would not show his face again...

Not until he understood who this new enemy was and how to destroy them.

The traumatic image of the dive bombing left a deeper scar than any internal wound from Yoriichi's Sun Breathing.

This wasn't power...

This was total annihilation.

Swish—swish.

In the blink of an eye, he had already sped dozens of kilometers away from the battle site. In his mind, one thing was certain: if he wanted to escape, there wasn't a single being in the world who could catch him.

---

And Yet—

"Safe?"

Muzan looked around. Silence. No sound of aircraft. No trace of Demon Slayers. Not a single creature seemed to be chasing him.

He started to feel at ease.

But just then—

Fiiuuuuuuhhh—!!

A soft sound, almost imperceptible... a hiss of wind slicing through the air behind him.

"Targeted?!"

Muzan's expression changed. "That fast?!"

His reflexes made him turn instantly, and there—he saw a small missile heading straight for him.

Because their relative speed wasn't too far apart, and thanks to his ultra-sensitive vision, Muzan had time to catch the details of the missile.

There was a strange logo on the warhead.

A bright yellow background with black dots, flanked by three fan-like rays emanating from the center.

Beneath it, a large black exclamation mark.

Radiation logo. The universal symbol for nuclear weapons.

"...?"

"What is this—?"

But before his mind could even finish forming a single hypothesis—

BOOOOOOMMMMMMMMMMMMMMMMM!!!!!!!!!!!!!!

A blinding white light seared his vision.

Instantly, the night sky turned into a second sun.

The shockwave swept through the mountains.

Nuclear fire exploded, forming a towering mushroom cloud.

The largest firework in world history... lit up the night.

And at the very center of the explosion—

Kibutsuji Muzan vanished without a trace.

Or maybe he's still alive after the nuclear bomb—who knows? It's not something that can be confirmed yet.