Crossover Shipgirls: Building a Dimensional Empire from Scratch

Half a year passed quietly.

Setsuna traveled frequently between Earth, the Starbase, and the planets of the Solar System, overseeing the full-scale development and construction of the home system.

In his free time, he spent it with shipgirls, Heroic Spirits, Spirits, and other companions.

In the interstellar era, the civilization’s expansion capabilities had grown exponentially.

After unlocking faster-than-light technology and fully upgrading the Angeloids and Bulins, the habitable planets in the Solar System and surrounding regions quickly entered a state of full-scale development.

They watched the Moon transform—from a barren, lifeless rock to receiving the first Bulin and Angeloid landings.

A small colony was established.

The colony expanded rapidly, aided by galactic-era technology.

Buildings rose one after another, artificial gravity was installed, and the thin atmosphere was altered.

The settlement grew into a small city, and eventually into a lunar research center the size of a satellite city.

Tens of thousands of loli researchers arrived on the Moon to begin new scientific projects.

Farther out, Mars, Mercury, Europa, Phobos, and other planets were entirely entrusted to Bulins and Angeloids for development.

According to the plan, they would be transformed into specialized worlds—forge planets, agricultural planets, and more—relocating most of Earth’s industry and agriculture off-world.

The goal: to forge a true utopian world.

...

One morning—

Setsuna was reclining in his chair, pondering the next stage of expansion.

The Illustrious-class sisters clustered around, tending to him.

As armored carriers, Illustrious, Formidable, and Victorious were... generously proportioned.

Unfortunately, Indomitable was a homebody and rarely left the house—always one short of the full set.

”Commander, do you want Illustrious to massage your shoulders?”

”Commander, let me~”

Illustrious and Formidable flanked him left and right, their... overwhelming presence filling his view with snowy white.

Paradise.jpg.

”Ah, let me just take a nap...”

Whoosh—

Just as he was enjoying himself, a holographic display popped up.

On-screen was Grey, the nanomachine girl, looking excited, with several Siren shipgirls beside her.

From the background, they were in the control room of a starship.

”Oh? Grey? What’s up?” Setsuna asked.

”Ahem.”

The nanomachine girl put on a serious face.

”My dear Commander, stop partying on Earth and flirting with shipgirls. I understand carrier shipgirls have their... appeal, but can we focus on serious business?”

”The Eternal Snowfall’s new hull is complete.”

”!!!”

Ten minutes later—

Whoosh—

The silver-white Aurora launched from Earth.

Carrying Setsuna, his accompanying shipgirls, curious Heroic Spirits, Spirits, and others, it sped toward the Starbase.

From the earlier reports, everyone knew this was an unprecedented upgrade.

The Commander had been stationed on Earth for a full year.

Using resources from over a dozen vassal worlds, and with the support of over a million specially-modified Bulins, the new hull had finally been completed.

The shipgirls were eager to see what kind of starship it was, while the Spirits and Heroic Spirits were simply curious about what new superpower their husband and Master had acquired.

Vmmm—

The Aurora skimmed past the orbits of Venus and Mercury.

Even before reaching the Starbase, they could see the massive silhouette docked at its side.

It was so enormous it dwarfed the Starbase itself, nearly the size of the Moon.

At its center was the starship’s main hull and bridge, over a hundred times larger than its previous form.

On each side stretched weapon wings thousands of kilometers long, each bristling with an uncountable number of turrets.

An ordinary starship’s entire hull wasn’t even as big as a single main cannon mounted on those wings.

The dark gray hull reflected the blazing light of the Sun.

It looked less like a starship and more like an asteroid-class space fortress.

”So big!!!”

Several shipgirls aboard the Aurora craned their necks, exclaiming sincerely.

When the Eternal Snowfall had first been built, it was barely over 600 meters—a mere interstellar frigate.

Multiple refits later had only pushed its size to around 10 kilometers, classifying it as a battleship.

After rescuing Grey, the nanomachine girl and the Siren shipgirls had combined the most advanced technology from Stellaris and Azur Lane.

With the Bulins’ absurd engineering prowess, they had produced this monster.

”I thought the Commander’s next ship would be a fifty or sixty-kilometer Titan, but I guess you went straight to the final form?” Harbin remarked.

The closer they flew, the more ridiculous the sheer scale of the vessel became.

The Aurora searched for a place to land but couldn’t find one.

In the end, they simply docked obediently in the shipyard.

Grey, Observer, Kayo Senju, and a special Bulin foreman were already waiting.

”Commander, what do you think?”

”This is the ultimate hull I imagined and built for you with the Sirens.”

”It represents the Starsea Empire’s current peak in astronomy, physics, and engineering—it’s the most powerful starship we can currently construct.”

The nanomachine girl stood proudly with her hands on her hips, her face practically reading: Praise me.

”Good work.”

Setsuna patted Grey’s head. Though she was a nanomachine collective, her temperature and texture were no different from a normal human.

”Onii-chan! Me too!”

Kayo Senju pouted and tugged at his clothes.

”The ship’s main design and technical challenges were solved by Grey-sensei, but our Imperial Research Institute also contributed a lot!”

”Alright, alright.”

Setsuna crouched down, straightened the little loli’s clothes, and handed her a box of delicate pastries.

”Whatever you want to eat or wherever you want to go, just say so.”

”Ehehe...”

The blonde loli hugged him, nuzzling happily. Compared to the other dark-haired lolis, Kayo was the smartest and most mature.

Nearby, the colorful Bulin looked envious.

”Bulin wants some too! Bulin’s tired! Bulin’s been helping build the ship for you!!!”

”Hmm... Once this project is over, you all can take a long vacation.”

Setsuna ruffled her hair as well, being fair to all.

From the ID tag on her chest, this colorful Bulin was clearly the foreman.

Bulin might be a little goofy, but she was still part of the Starsea Empire.

”Yay!!!”

She threw herself into a hug.

”Even though Bulin was made to strengthen the fleet, the Commander still values me so much...”

”Commander! I like you now, burin! As thanks, let me give you a special burin!”

Clack—

She pulled out a cat hammer, clearly intending to smack him.

”Stop!!! That kind of force isn’t for the Commander!!!”

”And Commander, seriously—don’t tell me you’re going after Bulins now too?!”

...

To board a Juggernaut the size of a small asteroid, Setsuna and the shipgirls had to take a shuttle.

The interior of the starship was vast enough to hold hundreds of regular battleships side by side.

Even Richelieu, Yamato, Taihou, and other shipgirls could materialize their full ship forms inside the Eternal Snowfall’s internal hangars without issue.

Grey, Observer, Kayo Senju, and Setsuna toured the Juggernaut together by shuttle.

Entering through the lower hatch brought them to the ship’s power module.

Contrary to expectations of a massive reactor, the Eternal Snowfall’s core occupied barely the space of six stories.

For a Juggernaut-class ship, it was surprisingly small.

”The ship still uses a Wisdom Cube drive, but considering the massive energy needs of this beast—and to make future upgrades easier—I also installed that,” Observer said, waving a tentacle toward the reactor’s center.

There, suspended in a force field, was a half-meter-long metallic cube etched with intricate lines.

It was small, but the energy it radiated was immense—clearly the main power core of the ship.

”The Allspark?!”

Setsuna recognized it instantly.

”You put it in the ship?! I thought you were still studying it!”

”To power a planet-sized vessel isn’t easy, Commander,” Observer-loli shrugged.

”Running a Juggernaut purely on a Wisdom Cube is barely feasible. We tried lifting the Cube’s output limit, but it was too unstable—not suited for you. The Allspark is the better choice.”

”Purifier separated a few Allspark replicas—enough for research.”

”This thing has creation-level energy. Whatever you decide to install on the Eternal Snowfall later, it can handle it.”

She said it casually, but Setsuna caught a lot in her words.

”Not enough power from the Wisdom Cube? Lifting the limit... you mean META-ization?!”

”Yep, you know about that?” Observer nodded.

”The Wisdom Cube’s output limit is capped for stability. Removing that limit might even let us make META shipgirls...

”Ahem, off-topic. Back to your ship.”

She tapped the holo-display, bringing up an ocean of data.

”In short—the Eternal Snowfall is now a true Allspark + Wisdom Cube hybrid battleship. Its energy capacity is essentially infinite.”

”Then why don’t I just absorb it?”

”You can—once you absorb the Eternal Snowfall, you’ll gain the Allspark’s abilities too,” she replied, scratching her head.

”We needed it for experiments during construction, so we just installed it directly.”

”Allspark abilities, huh...”

Setsuna’s expression turned wry, recalling the time the big-eyed mech had turned trash cans, vending machines, and cleaning robots into Transformers, sparking a riot.

”Sounds like starting a machine uprising...”

...

After inspecting the Allspark-powered core, they moved forward.

In the lower section were two enormous internal shipyards.

They resembled the Starbase’s docks, complete with assembly and repair facilities.

The berths alone spanned hundreds of kilometers.

The accompanying shipgirls could easily sail their full hulls inside.

”The Juggernaut has two internal docks—capable of assembling battleships, cruisers, destroyers, and other mid-to-small craft, and serving as frontline repair yards,” Observer explained.

”Each dock has three production lines, fully automated and run by Angeloids and AIs. For even higher efficiency, Onii-chan, I recommend bringing some Bulins along,” Kayo Senju explained.

”As long as resources are sufficient, the Eternal Snowfall can serve as a mobile operations platform.”

”Whoa—”

The shipgirls let out impressed sounds.

Before, when they were out on expeditions, any damage or maintenance required a return trip to the Starbase.

Now, they could just stay with the Eternal Snowfall.

It could act as the core, supporting an entire fleet in long-range operations.

On an interstellar scale, its role was similar to that of an aircraft carrier on Earth—except the ”aircraft” were starships.

”Commander really makes people feel safe...”

Even the usually independent Yat Sen couldn’t help imagining the shipgirls fighting under the protection of the Eternal Snowfall—no matter how powerful the enemy, this giant ship would shield them.

”Are you sure this thing won’t just become a giant target?!”

Gudako stuck her tongue out.

”The Eternal Snowfall’s bigger than the Moon—can’t you hit it with your eyes closed?”

”Do you even know how tough its energy shields and Klein fields are with the Cube and Allspark boosting them?” Grey shot her a look like she was an idiot.

”If it rammed Earth, it’d smash the planet to dust without a scratch on itself! Honestly, I think it could crash into a star and be fine.”

”I doubt any conventional weapon could even scratch it—and even if it did, the self-repair systems and Angeloid damage control would fix it.”

”Crash into Earth?!”

Everyone glanced at the blue planet in the distance and shivered.

In terms of sheer mass, the Eternal Snowfall hitting Earth would be no different from the Moon crashing down—except it was made entirely of high-strength alloys and had shielding.

”Commander, please be careful when landing. One mistake and our home’s gone...”

Kanae tugged at Setsuna’s sleeve pitifully.

”This thing can just stay in Earth’s orbit—normally I’ll use a smaller ship.”

The shuttle continued deeper inside.

On the ship’s two massive weapon wings were 60 spinal cannons each.

Where battleships once sacrificed mobility to mount a single gun on the keel, the Juggernaut treated them like bulk stock.

It had over a hundred hangars—more than all the carrier shipgirls’ planes combined.

Setsuna’s powerful mental strength could precisely control each craft, using short-range jump drives to strike directly at the enemy.

”Subspace lances, focused arc projectors, gigaton kinetic cannons—you name it,” Grey introduced each new weapon.

”All weapons are modular for easy replacement and upgrades.”

”In addition, there’s a colossus weapon launcher beneath the main hull—you can choose whatever planet-killer you want.”

She pointed to a flower-shaped launcher dozens of kilometers across.

”The default is the ’Neutron Sweep.’ It uses a high-energy neutron radiation stream to sweep a planet’s surface, killing all life while leaving structures intact—including microorganisms.”

”A planet hit by it won’t have a single bacterium left, yet none of its buildings will be damaged—maximum elimination of alien pests while preserving the spoils.”

”With the Eternal Snowfall’s power, it only takes half a day to completely cleanse a planet. Efficient, right?”

”...”

The explanation—so full of Paradox Interactive war-criminal flavor—unnerved several Heroic Spirits, Spirits, and non-combat girls.

Shattering a planet was easy with enough force—it could be done in an instant.

But eradicating only its life while preserving the planet intact was another matter entirely.

Such was the cold efficiency of interstellar-era weaponry.

Gudako suddenly recalled myths and legends Roman and Setsuna had once told her.

[The time of birth has come; with this, correct all creation.]

”Commander, is this an Anti-Humanity Noble Phantasm?!”

—

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