Crossover Shipgirls: Building a Dimensional Empire from Scratch

”The Wisdom Cube is the source and core of a shipgirl’s power—the projection of their rigging, their remote combat capabilities, all stem from it. You understand that, don’t you?”

Temperance looked at Setsuna and spoke softly.

”I do.”

Setsuna smiled faintly. Most of his own power also originated from the Wisdom Cube. The Cube was like a perpetual engine, working in tandem with the Allspark to continuously provide him with energy.

However, within the Starsea Empire, most Wisdom Cube research had long been delegated to the Experimentals, who were recruited early on.

The thing was simply too complex. Coupled with the incomprehensible craftsmanship of the Bulins, the Engineering Department had abandoned any attempt to study it years ago.

—After all, no one else could use it anyway. When a shipgirl needed one, the Bulins just made it. No one knew how it worked, but it always did.

The Sirens, being a branch of the shipgirls themselves, clearly possessed a much deeper understanding of Cube technology than the Starsea Empire.

”The power of the Wisdom Cube is restricted.”

Temperance spoke concisely.

”When the first shipgirls were created using Cube technology, Dr. Anzeel discovered that while the Cube’s power was immense, it could cause the shipgirls to lose control—resulting in what we now call META.”

”To prevent this, she installed a limiter within the Wisdom Cube to stabilize its power.”

”In many of the parallel universes we observed, we found another form of shipgirl existence—META shipgirls.”

”META shipgirls, at the same technological level, possess a far higher power ceiling than standard shipgirls. They are capable of completely releasing the Wisdom Cube’s full potential.”

”However, unlike normal shipgirls, their hearts hold nothing but war.”

”...”

META shipgirls—essentially the ’darkened’ counterparts of normal shipgirls.

”Uh, so like Jeanne d’Arc and Jeanne Alter? Or Saber and her dark version?”

Gudako propped her chin on her hand, trying to relate it to her extensive Type-Moon knowledge.

”You could say that.”

Setsuna nodded.

”They are an alternate form of existence, born from a different worldline.”

”Oh...”

The other shipgirls listened with keen interest. From the moment they had gained self-awareness, they had never left the port.

The idea that there existed darker, alternate versions of themselves was... fascinating.

”Are they strong? Stronger than me?”

Enterprise asked directly.

”...META Enterprise gave us quite a bit of trouble...”

Empress sighed.

”That woman required multiple Arbiters working together just to contain her. She even led an assault on the Siren mainframe once. A nightmare to deal with...”

”You might not fear her now that you’re a starship, but under equal conditions, META Enterprise is far stronger than you.”

”Hiss...”

Given that high-level Sirens could easily flatten the pre-starship port district, the fact that even they found META shipgirls troublesome spoke volumes.

”So basically, the dark version’s three times stronger.”

Setsuna wasn’t surprised. What truly interested him was something more practical:

”So... how do we make a META shipgirl?!”

Normal shipgirls, Experimentals, and now the Arbiters were all part of the Empire—if he could add META versions to the mix, he would have the full Azur Lane collection.

One could never have too many wives.

And with starship-grade refits, they’d form yet another unstoppable space fleet.

”...That’s quite a direct question, Commander.”

”Based on our observations and theories, there are two ways to obtain META shipgirls.”

Temperance took out a dark-colored Wisdom Cube.

It was the same size as an ordinary one, but a faintly terrifying power pulsed within it.

”The first method is to summon them directly using a META Cube. The second—transform an existing shipgirl by unlocking the limiter within her Wisdom Cube, allowing her to evolve into her META form.”

”The META state is irreversible. Which approach you take depends entirely on you, Commander.”

”The first one, obviously.”

Setsuna answered without hesitation.

Having both standard shipgirls and META shipgirls through method one—now that was double the joy.

”I understand.”

Temperance encased the dark Cube in a force field and handed it to Compiler.

”This is a META Cube we recovered from one of the experimental fields before the worldline collapsed. I present it to you as a small gift from us.”

”With the Starsea Empire’s technological prowess, analyzing and replicating its structure should not be difficult.”

”...”

Compiler used her mechanical claws to lift the META Cube, examining it closely before nodding toward Setsuna to indicate there was no issue.

”META shipgirls aren’t as gentle or compliant as regular ones,” warned another Arbiter—a silver-haired, blue-eyed woman clad in a translucent silk gown.

”Commander, leading them will be no easy task.”

”No problem.”

Setsuna waved casually, full of confidence born from years of experience managing shipgirls.

”...So now even shipgirls will come in multiple editions?”

Gudako muttered, her imagination running wild.

”The original ones who lived on the sea are Standard Shipgirls, after refitting into starships they became Starship Shipgirls—and now we’re getting super-limit META Shipgirls?!”

”At this rate, will we also get Magic-class Divine Shipgirls someday?!”

Setsuna thought for a moment.

”...Not impossible.”

”Wait!”

Suddenly, Observer—who had been snuggling in his arms earlier—raised her hand excitedly.

”I have a bold idea! We don’t need to give up on the shipgirl META-conversion plan!”

”?”

Dreamweaver and the other Arbiters turned to her in confusion.

”The second method could be used on the Commander instead!”

The little loli poked Setsuna’s chest with one of her rigging tentacles.

”The Commander already has two Wisdom Cubes inside him, plus the Allspark—that’s a triple-core structure!”

”So if we insert the META Cube too, it’ll become quad-core! Perfect!”

”With his adaptability to nearly all forms of power, he might even achieve a META version of the Eternal Snowfall! The normal form’s Fallen Star Lance can already shatter a sun—imagine what a META version could do!”

”???”

The Arbiters were momentarily dumbfounded.

”Put a Cube inside the body? How many can you even fit at once? Can a normal and META Cube even coexist?!”

”Not for others, but the Commander can handle it! The Eternal Snowfall already houses the Allspark and Herrscher Cores—you’ve never seen anything like it!”

Observer puffed up proudly.

”...”

Dreamweaver stared intently at Setsuna.

When she first met him, she had simply thought this ”Commander” shared similar powers with shipgirls—summoning ships, projecting rigging...

But upon closer inspection, she realized his power system was far more complex. Even within the Eternal Snowfall alone, multiple forms of energy coexisted and intertwined.

From the Siren perspective, his existence defied logic.

”What a peculiar being...”

Dreamweaver murmured softly to herself.

”Approved!”

Setsuna decided decisively, rubbing the little loli’s head.

”Go—this task is yours, Experimentals. The next phase of the starship project depends on you.”

”No problem~~!”

Observer nuzzled against his chest happily.

”Not only will we have META shipgirls, we’ll have a META Eternal Snowfall too!”

...

The twelve Arbiters of the Arbiter Organization, along with Dreamweaver, had temporarily settled down in the Starsea Empire.

On one side of the Starbase, within the starship docks—

Wumm—

Each of them projected their own vessel into physical form. Twelve uniquely designed ships materialized, their silhouettes shimmering across the berths.

”Waaah—”

The colorful Bulins hefted their hammers, standing atop the Siren hulls, knocking here and there.

”Never seen a structure like this before, buli...”

”It looks complicated... but also kinda outdated, buli...”

From the perspective of the ”locals,” the Arbiters’ ships looked like something out of pure science fiction.

Their streamlined designs resembled oceanic lifeforms, armed with carrier bays, main cannons, and mixed defense systems like shields and energy weapons.

Each was several times larger than a conventional aircraft carrier or battleship and could maneuver both in atmosphere and in space.

In the past, a single Arbiter could easily crush an entire naval fleet. But now, before a true interstellar empire, they still fell short of genuine starships.

”Hmm, the mobility isn’t enough, Buri~n! We’ll swap in warp drives—your Siren cores should have plenty of power for that, Buri~n!”

”And the shields! Ours are stronger! Way more durable, Buri~n!”

”All weapon systems—tear them out and rebuild from scratch, Buri~n!!!”

Within just a few days, the Bulins had dismantled every Arbiter ship completely—leaving nothing but the exposed central cores.

”Ugh—”

Empress, Lovers, and the others couldn’t help but feel an odd sense of embarrassment, as if they’d been stripped bare.

Thankfully, apart from shipgirls, Bulins, little lolis, and Angeloids, there were no outsiders at the Starbase.

Soon, reconstruction began from the ground up.

Each new hull was redesigned according to its Arbiter’s combat style, outfitted with the most advanced weaponry of the Starsea Empire.

Originally only a few kilometers long, the rebuilt warships now had keel frameworks stretching hundreds of kilometers—massive structures that seemed endless when viewed from space.

”Wow...”

”That Commander is really generous, isn’t he? Building this many giants must consume an enormous amount of resources!”

”We’re truly grateful to him~”

Empress gazed at her unfinished ship, excitement welling in her chest.

”According to calculations, the resources required to construct one of these vessels are enough to produce three full IX-class Enforcer fleets in the Mirror Sea,” said Temperance evenly.

”The materials used to rebuild twelve Arbiters here exceed the total resources we could extract from our entire original universe.”

”What?!”

Empress froze in shock before realizing a simple truth:

The Starsea Empire’s industrial capacity was on a completely different level.

To an empire spanning thousands of light-years and ruling over dozens of vassal universes, this was nothing more than a handful of resources slipping through its fingers.

—After all, there were still Bulins in the Solar System building Galactic Wonders! The amount of material they consumed was beyond astronomical.

”Still, to think we need shipgirls to rebuild our ships... tch...”

Lovers watched the busy Bulins with a complicated look.

”I once thought we would be the ones guiding the shipgirls and the Starsea Empire’s progress. Never imagined we’d have to depend on their help instead...”

”When we created the experimental field, who could’ve predicted the shipgirls would one day grow this strong? That we’d be relying on them of all people...”

The Arbiters still weren’t quite used to it—to have fallen from being the supreme authority of the Siren Legion to a group of ’locals’ needing assistance.

”...”

”Of course you do.”

Observer, ever smug, crossed her arms proudly.

”To other Sirens, you’re the Arbiters.”

”But to the Starsea Empire—you’re just beggars.”

”???”

”Hah?”

Empress felt it might be necessary to give the insolent little brat a lesson once her ship refit was complete.

”If they hadn’t met the Commander,” Temperance added flatly, ”the Experiment would have concluded within two to three years—with the Harbor’s total collapse.”

Temperance carefully studied the data regarding the Starsea Empire—especially the section describing Setsuna’s arrival at the Port.

”The Commander disrupted that experimental field using power from another world, causing the worldlines to collapse into a single one.”

”Also, the Bulin Fusion Proposal he devised... is quite imaginative. Most of the Starsea Empire’s construction and expansion projects were completed by the Bulins.”

”Not realizing the extent of the Bulins’ power before now was a grave oversight.”

The Sirens had spent a long time alongside the shipgirls, believing they already understood them well.

They had always assumed the Bulins were merely maintenance workers—harmless mechanics who helped with repairs and logistics.

But after learning about the Starsea Empire, every Arbiter shared the same bewildered thought:

”Wait, the Bulins can be used like that?!”

”...Even a pre-space civilization couldn’t have supported that many Bulins...”

”...”

After exchanging stunned looks, Lovers gazed at the distant starship factory and spoke quietly:

”In any case, I hope we’ll have a chance to show the Commander what the Arbiters is truly capable of someday.”

”Right now, the shipgirls seem to be underestimating us—even Observer’s thinking about rebellion?”

”Indeed.”

Empress, Devil, and several others huffed softly.

”I’ve no idea where she even got that idea...”

”But once our weapons and equipment are brought to the same level...”

”Heh, our power goes far beyond just operating starships.”

”We’ll show those kids what we can really do.”

...

Meanwhile, unlike the Arbiters who were impatiently waiting in the docks for their starship conversions to finish, Dreamweaver remained calm.

She had refused the offer to refit her own vessel and had been spending her days quietly within the Imperial Grand Library.

There, she meticulously read through every record related to the Starsea Empire.

From the Empire’s founding history and its conquests across countless worlds to the foreign technologies gathered from beyond the stars—she studied everything with equal seriousness.

Even the most monotonous subjects—physics, engineering, or the completely unrelated disciplines of mysticism and magic—she read with unwavering focus.

Her reading speed was astounding. With the processing power of the Siren mainframe augmenting her, she could analyze the full content of a book in moments.

Yet, compared to the infinite collection of the Imperial Library, her progress still seemed painfully slow.

No one knew what she was thinking. The little loli’s face was always expressionless.

Even when someone greeted her, she would only respond briefly and without emotion.

”Commander, is that little girl really the leader of the Sirens? She’s not what I imagined at all...”

Onboard the Eternal Snowfall, shipgirls would occasionally come to Setsuna to complain.

”I tried asking her about the Sirens’ true purpose—why they built the experimental fields, what they’ve been doing all this time...”

”But all Dreamweaver does is talk in riddles! Something about ’embers,’ ’ANTI-X,’ and the ’metaworld’—none of it makes sense!”

Formidable pouted angrily.

It was frustrating. To finally meet the leader of the Sirens and still learn nothing useful.

”Let her be.”

Setsuna chuckled softly.

”That’s just how Dreamweaver is. You can’t expect every Siren to act like Observer or Purifier.”

”Maybe after spending more time with her, we’ll start to understand her better. There’s no rush.”

As long as she was peacefully staying in the Empire, Setsuna had no problem letting her do as she pleased.

He vaguely remembered that, in the original story, the Sirens were created to oppose some unknown enemy—something referred to as ANTI-X (also transliterated as Antiochus), meaning ”the opposition to the unknown X.”

The Experimentals had mentioned it to him briefly before, but for now...

It wasn’t important. According to reconnaissance, the Azure world showed no signs of this so-called ”X.”

If it appeared someday, they would simply deal with it. If it couldn’t be defeated right away, they’d leave it be and continue expanding the Empire’s domain.

The multiverse was vast and full of extraordinary beings—each capable of handling whatever refused to yield.

”Hmm...”

”The Engineering Department has news. Compiler and the Bulins are working on decrypting and replicating the META Cube.”

Yat Sen glanced over the report.

”The META Cube’s structure is more complex than that of a regular Wisdom Cube. Decryption is expected to take around half a month, with higher resource costs as well.”

”Fine. However many are needed—make them.”

Setsuna approved the plan immediately.

After a moment of thought, he flicked open the star map before him.

”Perfect. While we wait for the META Cube project to finish... we can take care of a few other things in the meantime.”

—

—

40 Advanced Chapters Available on Patreon:

Patreon.com/DaoOfHeaven