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

"Tsk tsk tsk, he truly is the progenitor of all Oni."

"Even a low-yield nuclear bomb failed to kill him."

The deck of the Prinz Eugen was tense. There, Belfast dumped the battered, staggering body of Muzan before Reuel.

"So you creatures really are miraculous, huh? Only the sun can kill you?" Reuel asked, his tone flat but laced with curiosity.

Muzan lay limp, black smoke billowing from his mouth, though no air passed through it. He was still alive—in a way that defied all human logic.

A nuclear bomb at that range should have obliterated any being, even one with five brains and seven hearts. Even if they were born with three heads and six arms—it was still a nuclear bomb.

"I think the blast force was still too weak. Besides, he did manage to flee very quickly," said Sister Richelieu, her tone tinged with regret.

"I had to reduce the yield to the absolute minimum. Not even a tenth of standard strength. Otherwise, he'd have been ashes long ago," Richelieu added with a sigh.

"..."

"..."

Muzan couldn't even stand, let alone use his Oni techniques. He survived only thanks to the absurd vitality and legendary resilience of his kind.

With what little strength he had left, Muzan lifted his head. His vision was blurry, but something about Reuel felt familiar.

"Who... are you..." he rasped. "Have we... met before?"

Reuel kicked him.

"The last time we met, you tried to kill me just for appearing in this world. I started this game naked, and I couldn't even beat you then."

Muzan's eyes widened. He remembered. Reuel—the man who had mysteriously appeared on a holographic interface, and the girl beside him was still the same.

Her appearance had changed, but a shipgirl like her was too striking to forget.

"Don't kill me..." said Muzan, his voice hoarse and desperate.

As the progenitor of all Oni, arrogance was his lifeblood. But in the face of death, even pride could be cast aside for the faintest sliver of hope.

"And why not?" Reuel asked coldly.

"I... I can share my blood... Give you power and immortality beyond imagination."

"..."

"In that case," Reuel replied calmly, "you're better off dead."

He pulled out a syringe, drew Muzan's blood, and sealed it in a secure container.

"Tempting, but you'll make a better specimen for future study. The Magos Mechanicus will be thrilled to have a sample of your blood. After all, you are the king of Oni."

Muzan's face twisted in bitter despair. He had never imagined his end would be like this—so pitiful, so utterly lacking in grandeur.

"Oh? Were you looking for this?" Reuel said, pulling out a blue Aobanagiku flower from his pocket. He tossed it casually toward Muzan.

"This... This...!!"

Muzan's eyes went wide. Awareness returned to him in an instant, triggered by a single thing: the blue flower from the Other Shore—Aobanagiku—which he had long sought to shield Oni from the sun.

He clutched it with trembling fingers, full of yearning and desperate hope, caressing it slowly.

Muzan thought—if he consumed it now, could he recover his strength? Could he escape?

But before he could do anything—

Smack!!

The flower's color faded. On its petals, a smear of paint—left by Muzan's own hands.

"?????"

He stared at Reuel with hopeless eyes, silently asking, why are you so cruel...?

"You're the fool. Don't blame others," Reuel replied with not a shred of sympathy. "The flower from the Other Shore does exist. So... you can move on peacefully."

The morning sun rose slowly over the horizon. In seconds, its rays touched the body of Kibutsuji Muzan.

And just like some forgotten folktale, he crumbled into black ash. The sea wind carried him away toward the Pacific Ocean.

He vanished—forever.

---

[Current World: Kimetsu no Yaiba]

Mission Objective:

1. Destroy the Twelve Kizuki. completely

2. Eliminate the threat of "Oni" completely.

Rewards have been distributed. Host may return to the original world.

Side Mission:

Conquer the world of Kimetsu no Yaiba and obtain the soldier module and weapons module to summon equipment and troops from human factions across alternate universes.

As soon as Muzan disappeared beneath the sunlight, the system confirmed mission completion.

Reuel checked the rewards he received.

The first reward was the cultivation techniques of Sun Breathing and Moon Breathing—the styles once wielded by Yoriichi Tsugikuni and Tanjiro Kamado.

Sun Breathing enhanced swordsmanship with effects akin to fire enchantment. Meanwhile, Moon Breathing allowed the user to unleash blade energy like crescent slashes.

Second reward: Kibutsuji Muzan's Blood Demon Art, containing all sorts of bizarre and brutal techniques—from self-division, the dead baby posture, to whip-like thorn attacks.

Reuel stored both away. He planned to modify the Sun Breathing technique so it could be used by the Astartes across every chapter.

He imagined the mightiest warriors of mankind, wielding flaming swords in one hand and bolters in the other—a vision that brought a thin smile to his face.

Especially if, someday, he had to face threats from alien universes.

"...."

"...."

"Commander, are you really interested in learning techniques like these? I believe those breathing styles were once used by the Demon Slayer Corps," Belfast asked, glancing at him while adjusting her gloves.

"If you have free time, it wouldn't hurt to try one or two moves. Think of it as light training."

Reuel simply gave a faint smile. "Techniques like Sun Breathing… honestly, they're not exactly relevant for you shipgirls."

"You'd better ask Akashi to accelerate the upgrade process to turn you into proper starships. That's far more efficient for our future missions."

He crossed his arms and looked up at the sky. "That said, I'm still curious about the magic systems and cultivation techniques often found in Chinese novels. How exactly do they work? Are they comparable to psionics or The Force?"

To Reuel, there were only two power systems truly worth their salt: Psionics from Warhammer 40k and The Force from Star Wars.

Both had proven capable of altering the outcomes of intergalactic wars—bending reality, influencing willpower, even warping the laws of nature.

But magic? Cultivation? Too local. Bound to specific worlds or dimensions.

Still... Reuel couldn't make a definitive conclusion just yet.

Too little data. Too many unknowns.

"Maybe... breathing techniques could be turned into a mandatory physical training program for kids in the future," he mused, half-joking.

"P.E. class with Sun Breathing?"

One of Belfast's eyebrows rose. "Sounds... revolutionary."

The shipgirls smiled wryly. They knew those techniques weren't essential for them—their systems already defied organic logic.

But the idea that children of the Imperium might someday perform Hinokami Kagura as morning calisthenics... was oddly charming.

Secretly, they wished they could go to school too, even though Reuel never allowed them to join the Schola Progenium.

He was afraid they'd be corrupted into another generation of zealots chanting, "For the Emperor!", "Burn the heretic!", "Death to the xenos!", and the like.

No—these girls were too innocent, too soft-hearted to be stained by such doctrines.

Reuel had other plans—someday, he'd build a university just for them.

A true academic institution, not a war machine cloaked in faith.

"So, we're heading home now?" asked Prinz Eugen, who had been quietly monitoring the electronic map on the holographic screen. "I'm curious about Gundam Akashi's construction progress and the Imperial Palace project..."

"Home?" Reuel chuckled lightly. "Not yet."

He raised his hand and gave the signal.

"All units, form up. Set course northeast, 32 degrees—heading for Tokyo Bay."

He paused for a moment, then grinned.

"It's time to teach the shogunate of this island nation a long-overdue lesson."

"Open their ports. Liberate their trade! And... impose a population tax."

Swish!

As they entered open waters, the shipgirls leapt from the deck, projecting their physical forms onto the sea's surface. Their mechanical and semi-organic bodies formed a perfect line.

In the middle of the ocean, a colossal fleet emerged from beyond the horizon.

At the vanguard: the Richelieu-class battleship, white and gold, gliding with elegance but radiating pressure.

Behind her, two 30,000-ton armored carriers flanked her, packed with air squadrons and advanced launch systems.

To the left and right, heavy cruisers escorted them, followed by ranks of light cruisers and destroyers in flawless formation.

They cut through the waves heading south. The hulls of the ships left massive ripples.

This fleet moved like a host of war gods.

On the coast, local patrol boats flying the Japanese flag panicked and gave way.

They knew this fleet wasn't something they could handle with old torpedoes or 155mm shells.

In the Demon Slayer timeline of 1912, the national naval force only comprised about 50 ships, totaling around 70,000 tons—give or take, depending on weather and maintenance.

Compared to this Imperial expeditionary fleet, they were nothing more than ants before a Titan.

Radio communications lit up.

"This is Yokosuka Coast Guard! Please identify your fleet and state your purpose!"

A nervous, choppy voice echoed through the military channel. All ports along the coast scrambled to send signals, trying to reach the main carrier.

By protocol, foreign fleets breaching national waters without clearance could be fired upon immediately.

But not a single Japanese ship had the guts to be the first to pull the trigger.

Because on their radar screens, these steel monsters were the embodiment of annihilation.

"We are the Expeditionary Force of the Imperium of Man."

"Two days from now, we will make landfall in Tokyo Bay."

"Inform the shogunate to welcome the noble Emperor of Mankind... or you can die."