Crossover Shipgirls: Building a Dimensional Empire from Scratch

Conquering the Kantai Collection world took about twenty days.

Shortly after returning to the capital, it was already midsummer.

Summers in the Mediterranean were hot and dry, the sky cloudless, sunlight blazing down on the earth.

Though the capital now had many climate-control methods—be it magic or technology—making Earth a land of eternal spring wasn't difficult at all.

Still, everyone felt that experiencing natural seasonal changes was part of truly living.

In the northern Golden Horn, next to the Azure, Arpeggio, and Siren naval ports, a new pale-blue naval base had been built.

It bore the flag of the Kantai Collection world's naval base.

This base was specially arranged by Setsuna and built by the Bulins for the native shipgirls. Its internal structure was nearly identical to that of the Azure and Arpeggio ports.

When the native shipgirls first entered the capital, they were a bit reserved, but under the enthusiastic welcome of the Azure and Arpeggio shipgirls, they quickly bonded.

The sea was filled with shipgirls playfully running over the waves.

"Tch, now this is the life—"

On the beach by the shore, Setsuna lay under a parasol, watching the girls frolicking in the distance.

Every expedition deserved some downtime afterward.

With Constantinople's favorable conditions, skipping a swimsuit session in summer would've been a waste.

Shipgirls, Spirits, Heroic Spirits… even little lolis in the capital wore swimsuits to enjoy the summer beach.

Eye candy—serious eye candy.

The whole beach was filled with beautiful girls. Most shipgirls were splashing around at sea, while the little lolis gathered to build sandcastles and hold barbeques.

Harbour Princess, Airfield Princess, and the other two Fortress Princesses sat nearby with Northern Princess, each hugging a giant tub of ice cream and spooning it into their mouths.

They were usually quiet and didn't interact much, Abyssals tending to stick with their own.

"Mmm, yummy."

"Commander is a good person."

Northern nodded.

"Mm, he's a good person."

Northern's three older sisters agreed.

Good food, good fun—so much better than the endless battles at sea.

They even had advanced aircraft to play with.

Abyssal Fleet?

Doesn't exist. The Starsea Empire is home.

A bit farther away, Formidable, Victorious, Akagi, and several other shapely carrier shipgirls were playing beach volleyball.

They too wore swimsuits. The Azure Lane shipgirls' figures looked especially exaggerated under the three-piece designs.

The shipgirls leapt and spiked the ball.

Before the Commander, there was no need for modesty. If anything, they were eager to show themselves off.

Hoping the Commander might invite them to dinner, then... something more.

"..."

Setsuna watched, eyes fixed.

"The volleyball's so white—no, so big—wait, I mean the volleyball looks great."

"Isn't there a milk-volleyball world? Should we pull in Marie Rose?!"

He suddenly remembered a few collaboration shipgirls.

"Hm?"

Formidable noticed the Commander looking her way and perked up.

She jumped high for a powerful spike.

Boom—

The first sound was her swimsuit's button popping off.

For a busty dinosaur-class figure like hers, this was a common occurrence.

"Kya—"

Formidable crouched and clutched her chest, face red to her neck.

"Commander, don't look!!!"

The other shipgirls burst out laughing.

"If Formidable doesn't want him to look, it's fine to look at Taihou instead~ Taihou's not inferior to them~"

Taihou scooted in close to Setsuna on the beach.

Setsuna felt like his vision was instantly drowned in something soft.

"Taihou, take it easy."

"Be mindful of the setting, will you?!"

Richelieu smacked Taihou lightly on the head.

Aside from shipgirls, there were plenty of civilians around.

Girls from the Girls und Panzer world, little catgirls from the catgirl world, and others all watched the lively scene nearby.

"Mmm... After all the effort I put into building a harem palace, it's only right to throw a party—I mean, for bonding."

"Come on, everyone gather around."

Setsuna had always been honest with his desires. He rested his head on Kurumi's lap.

One arm casually pulled Shoukaku close.

Surrounded by Spirits, Heroic Spirits, and dragon girls—

Soft, and faintly fragrant.

"Commander, let me apply some sunscreen for you."

Origami Tobiichi pulled out a tube of sunscreen, squeezed some into her hand, and began rubbing it on Setsuna.

"..."

Setsuna was about to say that with his physical resilience, forget ultraviolet rays—even literally sunbathing in space wouldn't be an issue.

Thousands of degrees of solar wind and ejected stellar matter couldn't harm him in the slightest.

But then again, this was a swimsuit season tradition—so he agreed.

"Mmm, starting with your hands, then arms..."

"To fully block UV rays, every inch of skin must be covered."

Origami sat on Setsuna's legs, carefully applying sunscreen everywhere.

A cool, refreshing sensation followed each stroke.

Yat Sen sliced some fresh fruit nearby and fed it to him.

...

As the application continued, Setsuna suddenly felt something was off.

"Wait, Origami, don't you think there are some areas that clearly aren't exposed to sunlight?"

"Really? I think it's necessary—just in case."

Origami's expression didn't change.

"Commander, did you know prolonged exposure to UV rays can damage skin?"

"According to the weather report, today's solar radiation is especially strong. It's my duty to ensure your proper protection..."

"I brought three different sunscreens. Their combined effect is superior."

Deadpan nonsense was Origami Tobiichi's specialty.

She pulled two more unbranded cosmetic tubes from her bag.

"..."

Setsuna's face darkened.

"No. There's absolutely no way UV rays are reaching there. Let me go."

...

"..."

The other shipgirls were too stunned to speak by this direct assault.

They thought they were already pretty forward around Setsuna, but Origami still outclassed them.

"Dear husband, you're not planning to do anything outrageous in broad daylight, are you?"

Kurumi gently brushed a hand across his cheek, her crimson eyes full of teasing amusement.

"I don't mind, but who knows what the others will think of you~"

"Why not return to the Eternal Snowfall first?"

"Tch, what are you saying in broad daylight."

Setsuna teased her back with a click of his tongue.

"Kurumi, didn't expect your head to be filled with those kinds of thoughts. At the very least, wait till night."

"Otherwise, if everyone's sunbathing and I suddenly manifest a hull, wouldn't that be too jarring?"

"???"

The girl providing the lap pillow blinked, surprised by Setsuna's reversal.

She pinched his cheek hard.

"Dear husband, that's the last thing I wanted to hear from you."

"How many times have you bullied me per month? Easily ten to twenty times, right? Sometimes without even checking time or place—it's been really troublesome for me."

"There were a few times we almost got caught, remember?!"

"???"

Gudako perked up her ears.

"Details. I want time and place."

Whack—

Tohru chopped her with a hand strike.

"You talk big, but even if you knew, would you dare?"

"If you went, there'd only be one result—'Gudako, the Commander's out of strength, hurry up and push him!'"

"..."

...

A few days later—

Setsuna brought the native shipgirls and Northern's family to the Starbase.

All major starship retrofits were now conducted in the stellar shipyard.

Back when Grey was first brought back, she and the research loli had designed a new hull for the Eternal Snowfall here.

They often argued back and forth about various strange issues.

Setsuna was quite curious whether they had come up with anything new after all this time.

He cared a lot about how his ship would be designed.

"Commander, after over a month of research, we've compiled and referenced a vast amount of data and conducted many feasibility tests."

"As of now, we've completed the design for the Eternal Snowfall's new hull."

"Thanks to Professor Grey's advanced technologies, this will be an unprecedented upgrade."

In the engineering lab, Kayo Senju stood proudly as she reported the results of their work.

The Eternal Snowfall was the Empire's flagship.

Being able to personally design such a symbol of imperial might gave her immense pride.

The research lolis in the base had gone all out, pouring their entire knowledge into designing this giant starship.

Fwoosh—

A holographic screen projected a massive, unusually shaped starship. It didn't resemble the traditional streamlined or rectangular space battleships.

Its overall structure looked like outstretched wings.

The central portion housed a massive command bridge and a colossal cannon even larger than the current Eternal Snowfall.

Stretching out from both sides were mechanical wings spanning thousands of kilometers, packed with an uncountable number of axial main guns.

Beneath the ship was a small starship assembly and repair plant—just as its "Juggernaut-class" designation implied, it was a mobile interstellar fortress capable of producing ships during battle.

"It's huge!"

Setsuna and the accompanying shipgirls exclaimed in unison.

"This Juggernaut-class starship was designed based on the Creator's blueprints and tailored to the Commander's specifications."

"It represents the current limits of our physics, engineering, and astronomy—and is the strongest warship I'm capable of designing."

Grey tapped the screen and began explaining the specifications.

"The Juggernaut is about 1,200 kilometers long, with a wingspan of 3,600 kilometers—bigger than the Moon's diameter. In scale, it's essentially a small planet-class warship."

"As for the engine—drawing from our research on the Transwarp Key and some data in my database, the Eternal Snowfall will be equipped with a new type of warp engine, allowing long-distance spatial jumps."

"Wha—?!"

Just seeing the ship's scale made Setsuna and the shipgirls jump in surprise.

It was over 300 times larger than the current Eternal Snowfall—bigger than the Moon!!

The Juggernaut's size was simply beyond imagination.

Even those titanic ships imagined to be 60 or 70 kilometers long looked like toys beside it.

Grey had inherited the Creator's vast repository of advanced technology amassed over millions of years, and had further upgraded and refined it with her immense computing power and knowledge.

In other words, she now possessed arguably the most advanced engineering expertise in the Stellaris universe.

The improvement in starship design was revolutionary.

"There's no way that thing can land on Earth..."

Richelieu glanced at the star chart.

A 3,000-kilometer-wide ship trying to land would be like the Moon crashing into Earth.

Even with anti-gravity systems, planetary curvature would prevent it from safely landing on solid ground.

"If we need to land, we'll just take a smaller ship. The Juggernaut-class is a true space fortress—it can carry all sorts of ship classes inside."

Grey replied.

"Battleships, cruisers, destroyers... anything really. At the scale of the Eternal Snowfall now, it could carry all of them easily."

Ordinary starships carried shuttles for mobility.

For a Juggernaut-class the size of a small planet, fitting a few starships inside was no challenge.

Just board whichever one is needed.

"A true juggernaut—only it is worthy of being the Empire's flagship."

The shipgirls exchanged glances.

They noticed Setsuna and Grey shared a similar philosophy:

Bigger is better, more is stronger.

"As for weapons—the Juggernaut has space for 60 axial weapons per wing. You can install light lances, arclight cannons, kinetic railguns, or whatever you like."

"As for the number of secondary guns... forget it, I lost count. But the total is roughly equal to your current fleet combined."

"In conventional interstellar warfare, it could wipe out an entire advanced civilization's fleet on its own."

Grey zoomed in on the structural diagram.

"In addition, the new Eternal Snowfall can be equipped with two types of planet-killer weapons."

"On its underside is a neutron sweep device. It emits high-energy neutron radiation capable of exterminating all organic life on a planet—while leaving the planet's structure intact."

"Efficient. I like it."

Setsuna admired such a weapon. Not only could it annihilate enemies completely, it also preserved spoils of war.

"The main cannon is something we developed by combining Wisdom Cube technology with the World Cracker. It's also the feature I'm most proud of in this starship's design."

"We've given it a powerful name—Fallen Star Lance."

Grey pointed at the colossal launcher in the center of the ship.

"Huh?"

Setsuna didn't recall any planet-killer weapon with that name. It sounded like a brand-new invention by nanobots and the research loli.

"While you were off charming shipgirls in the Kantai Collection world, I wasn't idle. I spent a lot of time discussing with the Sirens how to integrate technologies from both worlds to build you a ship strong enough."

"That Compiler girl is quite capable—we got along well enough."

Grey's tone trailed off slightly.

"The Fallen Star Lance is the result of our collaboration."

"It's the ultimate creation of Stellaris tech, Cube science, and Siren engineering. A hybrid of the World Cracker and Wisdom Cube power."

"This main cannon is independently powered by Wisdom Cubes and over 20 reactors. It can deliver instantaneous, astronomically scaled strikes across vast distances."

Setsuna skimmed the technical schematics.

He didn't understand the details, but the general concept was clear enough:

This was a new weapon forged from the pinnacle of both Azure Lane and Stellaris technology.

The Sirens represented Azure Lane's highest level of science. Grey represented the most advanced tech of the Stellaris universe.

Together, they had developed a Siren-modified planet-killer.

"What's its power like?"

"The current Eternal Snowfall can shatter asteroids with its supergravity cannon. This has to be far stronger, right?"

The shipgirls, captivated by Grey's pitch, were eager to know just how destructive it truly was.

"In its base form, the Fallen Star Lance can easily break apart an Earth-sized rocky planet."

Grey hugged her ample chest with pride.

"The more Wisdom Cube energy it draws, the stronger it gets. With both of the Commander's Cubes at full output, even destroying a star wouldn't be difficult."

"—Honestly, destroying a star isn't as complicated as it sounds. You just need to pierce the outer layers and detonate the core. Even civilizations with sublight tech can do that."

"If you add more Cubes and ramp up output—reaching galactic or even cluster-scale destructive capability is possible."

"Anything beyond that... well, it's outside my current capabilities. You'd have to rely on the Commander's own resourcefulness."

Hiss—

Everyone was slightly shocked.

A Siren and a nanobot—two holders of vast black technologies—had created something truly terrifying together.

Setsuna looked up at the distant stars, deep in thought.

"The power to shatter stars and extinguish suns..."

"Fallen Star Lance—what a fitting name."

...

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