Crossover Shipgirls: Building a Dimensional Empire from Scratch

At the highest point of the Eternal Snowfall’s bridge lay the starship’s command center.

From here, one could look down upon the entirety of the colossal vessel—its towering hull and wings spanning over a thousand kilometers, brimming with weaponry. Through the transparent dome, the endless starlit sky stretched above.

During peacetime, it was an ideal spot for stargazing.

Setsuna lounged in a recliner, idly flipping through an old, timeworn book. The black cover bore incomprehensible, twisted patterns, and the strange text within was written in a language long forgotten.

Fortunately, the ship’s AI came equipped with a translation function, making it easy to read.

”Oh...”

He nodded occasionally. Even in the interstellar age, he still retained the habit of reading paper books.

Besides, this was one of the arcane texts he had brought back from the Nyarlathotep universe—each carrying faint traces of battle damage, as if they’d endured wars between gods.

”The Blind Idiot God, Azathoth, is their supreme deity. She sits upon the black throne at the center of chaos, ruling over all time and space.”

”Under her serve the Three Pillars: The Unnamed Darkness, the Nameless Mist, and the Messenger... specifically—”

As Setsuna spoke, his other hand slid around Scáthach’s slender waist, fingers brushing against the soft, smooth texture of her sheer black bodysuit—and the warm body beneath.

Scáthach leaned her head against his shoulder, her long hair draping over his chest as she listened intently to his explanation of the mythologies of another universe.

”Sigh...”

After a while, Scáthach let out a quiet, self-mocking sigh.

”The difference between gods and gods... may not be any smaller than that between an ant and a god.”

”If spear mastery truly reaches its peak—even the divine can be slain, yes? I was far too arrogant before.”

Listening to Setsuna’s words was eye-opening for her.

In the vastness of the multiverse, there existed countless pantheons beyond imagination. Compared to them, the gods she once defeated might not even qualify as divine attendants.

The Queen of the Land of Shadows—here, she was nothing more than a provincial native.

”You could always train more.”

Setsuna’s hand traced upward along her waist.

”When you’ve got nothing better to do, we can replenish mana again, then you can study new techniques in the Imperial Library. You might still get stronger.”

Ever since Setsuna had performed mana replenishment with his teacher, he had spent most of his free time aboard the Eternal Snowfall either accompanying other shipgirls or enjoying intimate moments with Scáthach.

In every way—her appearance, her temperament, her attire—she perfectly embodied his preferences.

She appeared cold and noble, always composed and dignified, like a distant queen. Which was precisely why, when her composure faltered and her consciousness blurred under his touch, that contrast was utterly intoxicating.

And that tight, see-through black bodysuit highlighting her curves? It was almost criminally effective—Setsuna sometimes thought taking it off would be a waste.

Though Scáthach had no prior experience in such matters, she had benefited from generous advice aboard the ship.

Under the guidance—and occasional demonstrations—of Jeanne d’Arc, Jeanne Alter, Origami, and even Taihou, she had learned a few... techniques of service.

”...”

Scáthach didn’t find it unpleasant.

Once, her standards were impossibly high—she believed that anyone worthy of standing beside her must be a warrior of unparalleled valor.

Now, she realized how shortsighted that had been. Her Master was no mere warrior—he was a commander, a ruler of a galactic empire.

Even the strongest warrior was, to him, just a brute.

”You use a spear,” Setsuna said suddenly, glancing toward the holographic interface. ”Speaking of which, maybe I can find a new weapon for you in the next world.”

He tapped the display and smiled faintly.

”Here—look. The Spear of Longinus, the god-slaying spear from the Christian pantheon. Seems like it’d suit you, don’t you think?”

”Can Heroic Spirits switch weapons? Want to try it?”

”Hm?”

Scáthach leaned closer, glancing at the screen before giving a soft laugh.

”Master, you really do have imagination...”

”If you wish to learn spear techniques, I could teach you a few moves instead. Since you can wield power from multiple worlds, you’d likely learn fast.”

”...Forget close-combat skills. Taixuan Eminence is enough.”

Setsuna chuckled lightly, pulling his teacher closer again.

He didn’t often rely on close-quarters combat—no need to waste effort there.

Then, as he thought about it, Setsuna suddenly found himself in the mood again.

”Hm... speaking of spear techniques, I suppose I could teach you a few moves myself.”

”What?”

Scáthach blinked in confusion.

She’d learned a bit about Setsuna by now—she knew he could wield divine sword techniques, that he commanded fleets and traversed the stars, but when had he ever learned to use a spear?

Before she could ask, Setsuna leaned close and whispered something in her ear.

Her brows furrowed slightly, a mix of amusement and embarrassment flashing across her face as she caught his meaning.

This kind of ”spear technique” was one she had been on the receiving end of several times in recent days.

Half protesting, half yielding, she bent forward—and soon found a long ”spear” pointed right at her face.

”Master, you really are... unbelievable...”

...

Time passed swiftly.

Morning sunlight spilled across the imperial capital. Little lolis, Angeloids, and Bulins began emerging one after another from their dormitories and docks.

The city gradually returned to its lively daytime bustle.

For them, it had been just another ordinary night. But aboard the Eternal Snowfall, due to the ship’s time-distortion systems, nearly two full months had passed.

”Mmh...”

Setsuna stretched lazily and sat up in bed.

”Mmm...”

The two Neros murmured in their sleep beside him, snuggled together. In this situation—bare and close—Setsuna honestly couldn’t tell which was which.

Thankfully, it didn’t really matter.

Scáthach stood before the wardrobe, picking through the remaining outfits.

She’d discovered that her clothes had essentially become consumables to Setsuna—and that, somehow, it was always the same few areas that ended up damaged.

After thinking it over, she decided it was fine—her Master would cover the expenses.

She casually pulled out a casual outfit and slipped it on.

Bang—

The door suddenly swung open, pushed by a gray-haired nanobot girl.

”Commander, you’re finally back, huh? Tch. First thing you do after returning is throw a party—you didn’t even come see me?”

Grey marched in, wrinkling her nose. There was a strange scent in the air.

She was holding a few data files in her hand.

”The missions we arranged earlier—several have been completed. Here’s the Wonder construction progress, and some updates from the Arbiters...”

”There’s a lot to go over. You’d better come to the Starbase to take a look.”

As she spoke, Grey suddenly froze.

Setsuna was gazing out at the distant stars through the window, his eyes unfocused—drifting somewhere far beyond the galaxies.

”Commander?”

”What are you thinking about?”

Grey waved her hand in front of him.

”I’m contemplating the meaning of life.”

Setsuna exhaled softly.

”The meaning of life is a philosophical question concerning the purpose and significance of human existence. It encompasses many related questions.”

”For instance: Why am I here? What is life? What is the true essence of existence? These are questions that science and theology alike have long pursued in their search for ultimate understanding.”

”In the vastness of the cosmos, what meaning does humanity hold? Does the universe itself possess a purpose—or is it merely a void construct of time and space?”

”???”

The nanobot stared at him, dumbfounded—nearly getting lost in the maze of philosophy herself.

After a long pause, she tentatively poked him in the shoulder.

”Commander, are you... having one of those post-party burnout phases?”

”...”

”Seems like it.”

...

Whoosh—

The starship slowly docked within the berthing area of the Starbase.

In one of the adjacent docks rested twelve massive vessels, each over a hundred kilometers long, painted in shades of deep blue and black.

Their main frameworks were already complete. Bulins and Angeloids were busily installing countless weapon and propulsion modules onto them.

The twelve Arbiters lingered nearby day after day, watching tens of thousands of Colorful Bulins perform modifications at absurd, lightning-fast speeds.

Setsuna’s journey to the Nyarlathotep world had taken only about three weeks, yet by the time he returned, the Titan-class warships were already entering the final stages of assembly.

”Wow, these little ones are really amazing. If only we had a Bulin Corps back in the day,” Empress muttered.

”Still, just sitting here watching kids do all the engineering work—I’m bored out of my mind. I hope they finish soon so we can finally go out for a stroll.”

Technically, they could have traveled using other ships, but for shipgirls, it was a matter of principle—leaving port without their own hull made them feel unsafe.

Thus, during refitting, they preferred to stay cooped up in the dock.

”I’ve already run twenty-six rounds of data analysis,” Temperance replied flatly. ”Given the Siren fleet’s strength and the current state of the Azur Lane universe, it would be impossible for them to maintain a Bulin army on the scale of billions.”

”Furthermore, based on current production rates, I estimate the Starsea Empire’s Bulin population will exceed five hundred million within a year, and when combined with the Angeloids, could approach one billion in two.”

”...Might as well rename it the Bulin Empire...”

As the Arbiters continued their banter, they suddenly noticed Setsuna descending from the ship.

They immediately straightened their clothes and gathered around to greet him.

”Commander?”

”Didn’t you say the new world was supposed to be difficult? We thought you’d be gone longer...”

Lovers naturally drifted close to his side.

”Oh, the Nyarlathotep world was... special. No real battles there, so the conquest went smoothly,” Setsuna replied, clearing his throat.

”My skills still have a few days of cooldown left, so I figured I’d come check on things here.”

His schedule was always packed.

During the cooldown period of his dimensional traversal authority, he used the downtime to process everything he’d acquired from the other worlds.

Before departing, he had assigned an enormous number of tasks to the Starbase—

Including, but not limited to: the refitting of Siren Arbiters, construction of multidimensional vessels, analysis of META entities, and the creation of the Galactic Wonder.

As Commander, he naturally had to perform regular inspections.

”Hmm...”

Like subordinates reporting to their superior, everyone gathered to brief him.

Half an hour later, in the Starbase conference room—

Daedalus, Grey, Observer, Kayo Senju, and other members of the Research Division sat before Setsuna.

Each held thick stacks of data, taking turns to report the empire’s research progress during his off-world campaign.

”The Arbiter refits are in their final assembly stage. Completion expected within a month,” said Observer, waving her tentacles.

”Once they’re equipped with advanced weapon systems and combined with their original abilities, we estimate that each Arbiter will be capable of single-handedly wiping out a standard Azur Lane fleet.”

During naval warfare, a single Arbiter could already devastate an entire port. Scaled up to starship-level combat, the results would be about the same.

Setsuna wasn’t surprised—the more shipgirls that could fight, the better. He was very much looking forward to seeing the Arbiters in action.

Richelieu and Formidable exchanged strange looks upon hearing themselves being treated as a combat unit of measurement.

”The Arbiters are really that strong? I don’t believe it. I’ll go see for myself,” Hakuryuu said, cracking her knuckles with a challenging grin.

”Sure, sure~ Kids who don’t listen always need a beating or two,” Observer said cheerfully, clearly enjoying the thought.

”The multidimensional vessel will take longer to assemble,” continued the big-eyed moe AI, projecting a detailed data report.

”This craft will carry prototype dimensional weapons, so we’ll need to conduct multiple test runs.”

It was a vessel built upon hope—designed to allow Setsuna to traverse beyond the bounds of time and space, to reach the future of worlds yet to come.

”Additionally, the construction of stellar megastructures is progressing steadily.”

”We’ve established more than sixty Gateway foundation sites across the Solar System and nearby star systems. Once completed, they’ll form a high-speed network throughout Imperial territory.”

Grey continued her briefing, highlighting the Engineering Department’s accomplishments on the star map.

”As for the Dyson Swarm, Matter Decompressors, and Arc Furnaces—most have completed site selection and structural frameworks.”

”Projected construction times range from one to five years. If we assign more Bulins, we can shorten that schedule considerably.”

”The Galactic Wonder, however, will take much longer.”

”Understood.”

Setsuna didn’t interfere much with specific construction details. Once the Engineering Department completed initial surveys and blueprints, everything else was handed over to the Bulins.

All they needed was an adequate supply of materials and a temporary base for them to work freely.

Whether the Bulins thought construction should proceed from inside-out or bottom-up didn’t matter.

If the Bulins said it was fine, it was fine. Their results had never failed before—no one dared question their process.

After listening to everyone’s reports, Daedalus raised her hand.

”Commander, regarding the Ascension project—those theoretical schematics and megastructure blueprints you provided—we’ve completed one of the core designs. It’s ready for your review and authorization.”

”Oh?” Setsuna tilted his head. ”What kind of structure are we talking about?”

”It’s... rather unique. You should see for yourself.”

Shhh—

The holographic screen flickered to life, displaying a massive hemispherical complex. From its edges extended countless mechanical wings, each lined with rows upon rows of life-support pods.

It resembled a giant, steel brain, bristling with neural cables and conduits.

Looking closer at the scale bar, one could see—it was far larger than an ordinary planet.

”This is a prerequisite structure for the Cosmogenesis Ascension—the Synaptic Lathe,” Daedalus explained.

”The goal of Cosmogenesis Ascension is to alter the universe through technological might—to rewrite the very laws of reality. To do so requires an astronomical amount of computational power.”

”The Synaptic Lathe harnesses the neural capacity of living minds to perform infinite simulations and calculations. Essentially, it is a storage-pool computing system.”

”It connects billions—even tens or hundreds of billions—of life-support pods to a central server, using their neural networks to generate computation and memory for the Empire.”

”Our most advanced supercomputers would only possess a fraction—perhaps one quintillionth—of its processing power. Naturally, such extreme extraction of biological cognition will inevitably result in... degradation.”

”...”

Daedalus summarized the concept as simply as she could, though the room fell into stunned silence.

In the ancient era, there had been a craze for ’mining’ virtual currencies with computers. The Synaptic Lathe was essentially that—except using human brains.

By sealing countless dissidents and undesirables into life-support pods, their minds were linked together to form a colossal neural computational network.

This would allow the Empire to process unfathomable quantities of data and perform calculations involving the deepest universal constants.

It laid the groundwork for rewriting reality itself.

Those confined within would experience perpetual immersion in blissful virtual worlds. In their dreams, they might be fleet commanders conquering galaxies, megacorp CEOs, or adored celebrities.

Through virtual reality technology, they would never awaken—content, unknowing.

Eventually, after years or decades, their brains would deteriorate under immense cognitive strain, burning out completely.

When that happened, they would simply be replaced—with fresh ”batteries.”

Anyone who entered the Synaptic Lathe was destined to become expendable.

Compared to exhausting the Empire’s resources to build a single supercomputer, the Synaptic Lathe was more efficient—more brutal.

And far more fitting for the Crisis Ascension.

The Crisis Empire was bound by no moral restraint. Discussing ethics with alien civilizations held no meaning.

It was a perfect way to extract every last bit of value from foreign insects and troublesome subjects.

”I like it. Approved for construction,” Setsuna said firmly.

”Grey, site selection is your responsibility. Begin immediately.”

”Uh...”

The nanobot girl wasn’t bothered by moral implications—she never cared for such things. She tapped her chin thoughtfully.

”The tech itself isn’t complicated. Usual procedure—leave it to the Bulins. I estimate it’ll be finished faster than most of the other megastructures.”

”But... what about the, uh, people used as fuel?”

”Oh, that’s easy.”

Setsuna nearly laughed.

”In the vast cosmos, you think we’ll ever run out of troublesome citizens to burn?!”

—

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