Crossover Shipgirls: Building a Dimensional Empire from Scratch

Whoosh—

The starship’s thrusters roared to life, propelling it steadily forward.

With the aid of advanced sensors, Setsuna easily locked onto the location of the Demon King’s castle and set the course to full speed.

”Eh?! Eh?!”

”We’re going to fight the Demon King now?!”

After a short exchange, Eris was just as panicked as Aqua had been earlier.

”Are you really not going to level up in Axel first? Maybe get some equipment? Even if you don’t like the starter town, there are other nations, dungeons to explore—” she said earnestly.

It was her first time seeing a hero who had been summoned for less than a few hours and was already rushing headlong toward the Demon King’s fortress.

”No need,” Setsuna replied calmly. ”The sooner we eliminate the Demon King, the better. Don’t worry—we have extensive experience in efficient extermination.”

”Well… I suppose that’s true…”

Eris looked a bit embarrassed.

After all, it was her world’s problem to begin with—and it now required Heaven’s intervention and Aqua’s meddling to summon heroes from beyond to defeat the Demon King.

She was genuinely grateful to every hero who came to help—even if this one was… strange.

”Come to think of it…” Tohru’s gaze drifted between Aqua and Eris.

”You goddesses aren’t nearly as strong as I imagined. Honestly, you two look like you’d lose to Gudako in a fight.”

The dragon girl frowned. Her image of gods didn’t quite match the two before her.

”This is my human body. I can’t use my divine powers,” Eris explained helplessly. ”Manifesting our true forms on the mortal plane is troublesome. Even Lady Aqua’s current state—her divine body—has its abilities heavily restricted.”

”So basically, nerfed,” Setsuna said dryly.

He wasn’t surprised.

As the Goddess of Water, Aqua was by no means weak. In theory, summoning a world-ending flood shouldn’t be difficult for her. She also possessed numerous unique skills—like dealing extra damage to the undead or dispelling curses.

But judging by her current state… it seemed her intelligence had also been nerfed upon descending.

”Then why don’t you just gather a dozen other goddesses from Heaven and gang up on the Demon King?” Tohru asked curiously. ”Even if he’s strong, there’s no way he could win against a divine mob.”

”The rules don’t allow it,” Eris said, shaking her head.

”Each heavenly goddess governs her own world. Normally, we’re forbidden from intervening in another goddess’s domain. Lady Aqua being dragged here by Mr. Setsuna likely exploited some kind of loophole.”

”I didn’t want to be dragged here!!” Aqua shouted, stamping her foot.

”...”

”Strange rules,” Mio and Tohru muttered to each other.

But after a moment, it made sense—if Heaven could just send down an army of goddesses every time, heroes would be redundant.

”That’s just how Heaven is…” Eris sighed, a trace of bitterness in her tone.

Life up there was, frankly, lonely.

”Don’t worry,” Setsuna said casually. ”Once this is over, I’ll take you somewhere far more interesting. My world’s still short on gods, after all.”

Whoosh—

While they chatted, the ship’s AI suddenly blared an alert.

[Target detected: 3 kilometers below.]

”Hm?”

Setsuna opened a holographic display.

On the barren plains below, a headless knight clad in armor rode a horse, leading a troop of monsters marching toward Axel.

”The Demon King’s army!” Eris exclaimed.

”That one looks like one of the Demon King’s generals!”

”Oh, Dullahan Beldia, right? I remember him,” Setsuna said.

In the original story, he’d been dispatched to Axel after Aqua descended to investigate the disturbances—only to get utterly humiliated and beaten down.

Judging by the situation now, history seemed to be repeating itself.

”Be careful, the Demon King’s generals are extremely powerful! Even veteran adventurer parties can barely defeat them…” Eris warned.

Before she could finish—

”Never mind,” Setsuna said casually. ”We’ll clear them out along the way.”

Zzz—

The cannons beneath the starship began charging.

”?”

Down below, the Headless Knight was riding his horse, his severed head tucked under one arm.

Suddenly, everything went dark.

He lifted his head to look upward—

Zzzraaa—

BOOM!!

A blazing beam of light descended from the heavens, carving a crater several kilometers deep into the ground.

The Headless Knight—and his entire marching army—were vaporized in an instant.

The starship didn’t even slow down as it continued toward the horizon.

”Abba… abba…”

Eris and Aqua were too stunned to form words, their brains short-circuiting from the sheer power they had just witnessed.

Two minutes later—

The ship’s AI sounded another alert.

[Target detected, northwest—1.8 kilometers.]

”Ah! That’s Duke—the fallen angel! She used to be a lower-ranked angel in Heaven before joining the Demon King’s army. She’s capable of—”

Zzzraaa—

Another light spear shot down.

When the dust cleared, there was only a massive smoking crater left behind.

[Target detected, north—1.9 kilometers.]

”That one too! Another general of the Demon King’s army! It’s a Deadly Poison Slime—it can mimic anything it eats—”

”Can it mimic a corrosion missile?” Setsuna asked dryly.

”Eh?”

BOOM!!!

Two dark-red missiles streaked across the sky, slamming into the ground and detonating into a spherical annihilation field.

Everything inside was erased at the molecular level.

”Guess not,” Setsuna said with a shrug.

”...”

As the ship continued its short journey toward the Demon King’s fortress, both Eris and Aqua fell into deep existential contemplation.

Why… why was there a hero like this?

Had the era changed that much?

He was wiping out the Demon King’s army like squashing bugs—no, worse, like swatting flies—with a casual press of a button.

Every past hero had struggled desperately against even one general. Now, those same monsters were dying before even realizing what killed them.

”Lady Aqua… what… what is happening?” Eris asked weakly, still in shock.

”...”

Aqua stared blankly for a long moment before finally speaking, her tone uncertain but oddly reverent.

”Maybe… this is what a true hero looks like?”

”Maybe all the heroes we summoned before were just… too weak?”

...

Far from the plains of Axel—

At the top of the Demon King’s Castle.

The fortress loomed like a massive citadel, its entire structure protected by an unbreakable barrier.

Even the Crimson Demons, as reckless as they were, couldn’t scratch it with their Explosion Magic. Ordinary adventurers or heroes stood no chance of breaching the defenses, much less reaching the top floor guarded by layers of Demon King’s generals and elite demons.

From the lower floors to the summit, each level was a gauntlet. At the peak stood the ruler of the Demon Race and commander of the Demon King’s Army—Devil King Kyoichi Yasaka.

”The light over Axel… what was that, I wonder…”

Kyoichi Yasaka gazed toward the distant sky.

Not long ago, from his castle, he had witnessed a beam of divine light strike down upon Axel.

Such overwhelming energy was beyond anything in this world—stronger than any adventurer, demon, or hero.

Only a god could possess such power.

Thus, he had sent one of his generals, Beldia, to investigate.

”If it’s just a starter town… there shouldn’t be anything of note. Hmph, whatever.”

He turned his attention back to the castle.

Though he was the Demon King, commanding countless subordinates, his underlings often gave him headaches.

Not one of his generals could be called ’normal.’ They were constantly causing trouble.

”Yasaka,” he called to his daughter.

”Take your troops and go check on Belzegu’s area. There are adventurers forming a party nearby—stop them before they get too close.”

”And take plenty of soldiers.”

”Tch—why can’t I just go attack the Crimson Demon Village?” she grumbled.

”They’ve been using scrying tools to spy on the Demon King’s Castle—and they even turned my room into a sightseeing attraction!”

”...Calm down.”

Kyoichi Yasaka sighed.

The people of the Crimson Demon Village were all… insane.

If you couldn’t solve the problem, you simply had to learn to live with it.

Following his orders, Yasaka’s daughter gathered a division of the Demon King’s Army and departed.

”Be careful out there,” he said.

”...You too, Father. Try not to get found by some random hero.”

”Hmph—”

Kyoichi Yasaka smiled faintly, looking down from the highest balcony, his eyes filled with confidence.

”My barrier is impenetrable. No one can break through it.”

”And even if someone did… they would never make it to me alive.”

Though past his prime, Yasaka’s support-type abilities made him a formidable foe. He could greatly enhance his subordinates’ strength—turning even ordinary monsters into general-level threats.

Any hero attempting to storm the castle would have to carve their way through countless buffed, high-level demons before reaching him.

”...”

Kyoichi Yasaka found himself a little bored.

Out of curiosity, he often pondered the origins of these so-called ’heroes.’

This world, after all, was full of mysteries.

Every few years, strange beings appeared—humans with bizarre ’cheats’ or ’divine blessings,’ proclaiming their mission to defeat him.

And then there were those rumors about ’goddesses’ and ’islands across the sea’—concepts that seemed to have some hidden connection.

”Haaah…” he exhaled softly, mulling over his next move.

But then—

Far in the distance, he noticed a small black dot in the sky.

His senses were sharp. He frowned and focused his gaze.

At first, he thought it was some flying monster—but the dot rapidly grew larger, larger still, until it became a colossal starship descending straight toward the Demon King’s Castle.

At the same time—

Whoosh—

BOOM!!!

RUMBLE!!!

The starship’s path was marked by roaring explosions. Its high-energy lasers and corrosive missiles rained down along the route, blasting the Demon King’s Army below into utter chaos.

The Demon King’s army crumbled like sand before the storm.

Even dragons and flying serpents that dared approach the ship were instantly shredded to pieces by its point-defense cannons.

”???”

”What in the world is that?!”

The Demon King shouted in disbelief—the same kind of cry Aqua had made when she first saw the starship.

”Could it be… the Mobile Fortress Destroyer?!”

Kyoichi Yasaka’s mind flashed back to that monstrous creation—a superweapon once built by a distant kingdom, pouring its entire treasury into its construction. It was meant to be a weapon against the Demon King, but had gone berserk instead.

The Destroyer possessed terrifying offensive and defensive capabilities—leaving only devastation in its wake.

Only the barrier surrounding his Demon King’s Castle had been strong enough to withstand it.

But the starship before him… was far beyond even that.

”...”

”Hmm…”

High above the world, Setsuna gazed down at the dark fortress encased in its massive barrier.

From the ominous aura it exuded, and the distorted shapes of the monsters crawling within, there was no mistaking it—this was their destination.

”Hiss…”

Both Eris and Aqua felt an instinctive chill run down their spines.

Their divine power was heavily restricted in their mortal forms, and the Demon King of this world had grown abnormally strong due to unforeseen circumstances.

Most heroes couldn’t even approach the castle, much less reach it. But thanks to the starship, Setsuna had casually wiped out all the Demon King’s generals along the way.

”So, who wants to fight the Demon King?” Setsuna yawned lazily. ”Or should I just nuke him?”

”?”

The two goddesses stared blankly. It was their first time seeing a hero so uninterested in fighting the Demon King himself—and instead offering the chance to others.

”I’ll go,” said Fu Hua firmly, stepping forward. It was her first interdimensional campaign, and she was eager to test her strength against a so-called Demon King.

”I’ll assist you,” Mio smiled faintly.

Clap—

[Ain-Soph]

The world turned black and white.

Time stopped.

”!”

Aqua and Eris could feel it—the very fabric of existence trembling. Their astonished expressions froze in mid-motion.

Then the Spirit of Origin raised her finger and tapped the air lightly.

Crackle—Crack! Crack!!

As color returned to the world—

The Demon King’s Castle’s barrier shattered like glass.

”!!!”

Kyoichi Yasaka barely had time to comprehend what had happened.

It wasn’t brute force that had broken the barrier—it was as if its very rules had been erased from existence.

”What…”

He looked up.

From the heavens descended a silver-haired, emerald-eyed immortal—Fu Hua—wielding the Xuanyuan Sword, diving straight toward him.

Having fused with Chiyou, even in her youthful form, Fu Hua’s strength had grown immensely. Every potion, every artifact, every training session had honed her power further.

Now, before this world’s final boss, she was eager to test her might.

”A swordswoman?!” Kyoichi Yasaka reacted swiftly, meeting her strike.

Her attacks were sharp and divine—nothing like the crude slashes of mortal adventurers. She forced him onto the defensive, his spells and curses struggling to keep up.

Before long, the battle drew the attention of the remaining generals.

”Attack!”

The Demon King’s army swarmed upward to surround her.

”Your swordswoman companion’s getting surrounded! Aren’t you going to help?” Eris asked nervously as hundreds of demons converged.

”If Fu Hua really can’t handle it, I’ll step in,” Setsuna said calmly. ”But… doesn’t it look like she’s gathering them?”

”What?”

Neither goddess understood—until they saw it.

Fu Hua stepped back, floating above the battlefield, and began to chant softly.

”Fire above, fire below—light of the burning heavens!”

BOOM—

The skies above the Demon King’s Castle ignited in crimson.

Massive quantities of Honkai energy condensed and twisted, turning the entire sky into a sea of living flame.

”...You’ve grown a lot stronger,” Setsuna said, looking up.

The energy she released now was far more immense than before—several times greater than her previous peak.

”???”

”Is this… swordsmanship?!” Eris blinked, speechless.

”High-level sword arts don’t need a sword,” Setsuna said simply.

Shing—

The seething Honkai energy took shape—forming a colossal golden blade that fell like divine judgment.

[Taixuan Eminence!]

BOOOOM!!!

The sacred sword crashed down, annihilating everything within its reach—body and soul alike.

The Demon King didn’t even have time to react. Both his physical and spiritual forms were obliterated simultaneously.

He couldn’t analyze the attack, couldn’t defend against it—he simply ceased to exist.

RUMBLE—

Honkai energy rippled through the castle. The upper guard unit, led by a horned beast, was erased instantly.

Even lesser monsters caught by the shockwave turned to dust.

”Cleanup complete,” Setsuna said, clearing his throat. He opened the hatch and released a few Angeloids to begin post-battle work.

Then, glancing at the dumbfounded Aqua and Eris beside him, he smirked.

”What’s wrong? Never seen a speedrun before?”

—

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