Crossover Shipgirls: Building a Dimensional Empire from Scratch

Watching the massive warship transform into a human girl before their eyes, then boldly say such wild words to the Commander, the Eternal Snowfall and the entire fleet immediately descended into chaos.

”Y-you-you... Who even are you?!”

”Pest! Another pest trying to steal the Commander!!!”

Taihou launched over a hundred aircraft, which buzzed and circled tensely around the Eternal Snowfall.

While some shipgirls had attempted subtle or flirtatious advances toward the Commander before, it was the first time anyone had so bluntly and directly demanded ○○ upon meeting.

No matter how you looked at her, she didn’t seem like a friendly guest.

Clack—

Setsuna took the initiative and opened the hatch for her.

The girl strolled inside, glancing around with curiosity.

”So this is an organic ship? Hmm... primitive but interesting structure.”

”But why do I smell something a bit different?”

With everyone staring at her in shock, she wandered the ship like she owned the place.

When she reached the control room, she examined Setsuna and his companions up and down.

”Hmm, you all have one head, two arms, two legs. Much more pleasant than those nasty guys with two heads and a tail.”

”Ah, such nostalgic organic lifeforms.”

”???”

The nearby Spirits and dragon girls twitched.

Her method of evaluation was certainly... unique.

”Who exactly are you? Are you the ’Grey Tempest’ the Commander mentioned?!”

Mio frowned.

”Yes, that’s me.”

”You know my name?”

The girl nodded, her expression a bit strange.

Seeing that the others were still confused, she decided to explain her origin.

”The creators of the L-Gate must’ve left you some messages, right? Long ago, in this star system, a civilization created a universal type of nanobot.”

As she spoke, she wandered leisurely through the control room.

”Because of their color and properties, these nanobots were called the ’Grey Tempest,’ though our internal designations are countless times more complex.”

”Eons after our creation, war broke out between the creators and the nanobots. It engulfed the entire cluster. In the end, only the nanobots survived.”

The shipgirls gazed out at the wreckage beyond the viewport. It wasn’t hard to imagine how devastating that war must’ve been.

”At the final moment, the creators sealed the Stargate. Those strange mechanisms can only be activated from the other side of the Milky Way. They hoped to trap the nanobots here forever.”

”After that, the nanobots realized... they had all the time in the world.”

”They began experimenting with various forms and transformations, trying to leave the cluster—but it was all in vain.”

”The nanobots once became planet-sized fleets of Grey Goo, dragons the size of stars, even reconstructed the exact civilization that created them.”

”Every citizen, every molecular layer—the nanobots could simulate every detail imaginable.”

Kayo Senju and the loli scientists held their breath in awe.

Simulating an entire civilization at the molecular level!

Even just listening to the explanation, it was obvious how powerful and bizarre these nanobots were.

Then, the girl stood directly in front of Setsuna.

She tapped her chest and raised her head proudly.

”And I—am their latest experimental result.”

”All surviving nanobots in this cluster, the entire ’Grey Tempest,’ are concentrated within me.”

”My consciousness represents the whole civilization. I am the pinnacle of artificial intelligence in this universe—you may call me Grey.”

”!!!”

Setsuna had mentally prepared for this. As a seasoned Paradox Interactive veteran, he knew Grey’s background well and calmly listened as she repeated the lore.

The shipgirls, on the other hand, were absolutely horrified.

The girl before them was, in truth, a collective civilization—her essence composed entirely of countless nanobots.

Through extremely advanced technology, these nanobots could simulate every hair, every tooth, even every cell in a human body.

At the same time, the nanobots could freely alter their form, just as she had transformed from a warship into a humanoid.

”Why do you look like this?”

Kurumi Tokisaki tilted her head curiously.

”Because I thought taking on the appearance of your species would aid communication. I extracted your appearance data the moment you entered the L-Gate.”

”Of course, if you don’t like it, I can change to something else.”

”No, this is fine!”

Setsuna quickly shut that down. He looked her over again.

Her current form was great, but compared to the Azur Lane shipgirls, it felt like something was still missing.

”Can you adjust your figure?”

He asked tentatively.

”Hmm? Which part? Head? Arms? Legs?”

Grey blinked.

Setsuna pointed at his own chest:

”A bit bigger.”

”Easy.”

Snap!

”Bigger, bigger, bigger...”

In seconds, she went from A to B, B to C, then to D.

Her outfit, also simulated from nanomaterials, expanded perfectly in sync.

Just as she was approaching aircraft-carrier-tier proportions, Setsuna coughed.

”That’s good. Perfect.”

”Alright, I’ll record these parameters and keep this form from now on.”

Grey cheerfully gave a firm nod, puffing up her chest.

”Hey!!!”

”What kind of cheat ability is that?!”

Nearby, a certain pink-haired shipgirl bit her kerchief in pure envy.

How was it fair that someone could just grow or shrink at will?!

”Um... do I still have a chance? Could you teach me?”

Saratoga glanced down at her utterly flat deck and shuffled over hopefully.

”...Uh... you?”

Grey studied her briefly, then raised a hand.

Whoosh—

A gray mist surged, and two silicone-like hemispheres formed in her palm.

The color and shape looked dangerously close to being censor-worthy.

”I can make a fake one from nanomaterials for you. Just wear it.”

”Don’t worry, it looks and feels just like the real thing! Any size you want!”

Grey seemed genuinely proud of her helpfulness.

”N-no!!!”

”What shipgirl would wear something like that?!”

...

After the chaos caused on the bridge by Grey and the very flustered Saratoga, Richelieu refocused on the important matter.

”So, what do you intend to do?”

”You’ve destroyed your creators and lived alone in this cluster for millions of years. Now that the Commander has opened the Stargate, are you planning to sweep across the galaxy like a natural disaster?”

Intuition told them Grey was relatively friendly. Aside from her unusual way of speaking, she left a good impression.

”Hmm... I suppose I should try something new...”

Grey plopped down on the floor, legs crossed, thinking aloud.

She looked at Setsuna, then at the dragon girls, the shipgirls, and the Spirits.

”Want to join us? Our home system is in the Milky Way, on the edge of the third spiral arm. We’re working hard to rebuild our civilization.”

”We’re also exploring other worlds and recently found some really interesting ones.”

Setsuna opened a star map before her and offered a straightforward invitation.

He had recently discovered several new worlds that seemed like ideal places to bring along a nanobot companion like her.

”Oh?!”

”You guys can travel between universes now?! I underestimated you!”

Grey jumped to her feet, eyes glued to the star map.

She shook her head.

”No, I can’t. We’ve barely known each other for two standard hours and you already want me to pledge myself to an alien I’ve just met?!”

”I know nothing about your bizarre country or your society. For all I know, you’re planning to use me for some shady scheme!”

After a bit of theatrical complaining, she scratched her head and looked Setsuna over again.

Suddenly, she changed her mind.

”Alright, let me join. I’m serious—building an interstellar empire alongside organics sounds fun.”

”I think I’ll get along great with you and your companions. And besides, it sounds like a thrilling adventure.”

As she spoke, she gave her body a swipe.

Nanobots shifted once more, reconstructing her outfit.

She now wore the exact same dark uniform as the shipgirls, complete with the Starsea Empire insignia.

”Hereby, I pledge my loyalty to you for the next 2,000 years—no, make that 5,000!”

...

Whoosh—

On the return journey, the Eternal Snowfall had a new passenger aboard: a nanobot.

There was no dramatic space war. Grey hesitated only briefly before decisively joining them.

And she very naturally stuck close to Setsuna.

After being trapped in the L Cluster for countless eons, she was unfamiliar with everything in the outside world.

”It’s so wonderful to meet organics again. Back there, I could only play with myself.”

”But you guys sure have a lot of species diversity...”

Grey eyed the crew gathered on Setsuna’s bridge.

Humans, shipgirls, Spirits, dragon girls, demons...

It was like a walking color palette.

”I’m the Commander here, and the leader of the entire empire. Welcome to the Starsea Empire family.”

Onboard the Eternal Snowfall, Setsuna held a formal and ceremonious welcome ceremony for her.

He even arranged for the Bulins to issue her a proper regulation uniform.

”Hmm...”

Grey changed into the black-and-red uniform and seemed quite pleased with the small gift.

Richelieu took on the role of tour guide, explaining the base layout and rules.

”We are currently a newly spacefaring civilization, having just developed FTL technology. Population is around 20 million...”

”The capital’s main population includes shipgirls, Bulins, children from the Black Bullet world, and Angeloids...”

”As for the vassal worlds, the situation is as follows...”

With the help of holographic displays, Grey’s expression grew more astonished the longer she listened.

She found Setsuna’s civilization structure truly fascinating.

”So your empire is composed of 3 million loli scientists, 17 million Bulins and Angeloids, and a few elite members?”

”Your resources come partly from domestic development and partly from tributes from vassal worlds.”

”By implementing sustainable pillaging across vassal worlds, you’ve achieved peace and unity in the home world?!”

”And your scientific progress is actually a conglomeration of multiple worlds—not just tech-based, but also full of vague, unexplainable occult elements?”

Nanobots possessed incredibly powerful logical thinking. From just the data and the shipgirls’ accounts, Grey quickly grasped the full picture.

Setsuna took a moment, then nodded.

He slightly corrected a few things.

”Strictly speaking, we don’t yet have 3 million scientists. Most of the lolis are still studying.”

”Only a handful of top-tier geniuses can finish all standard curricula and cutting-edge theory within a few years.”

”...Interesting.”

Grey gazed at the shipgirls and Angeloids thoughtfully.

”Studying your civilization’s structure sounds like a fascinating and never-boring endeavor.”

”Do you have any plans for your time here?”

Belfast politely asked Grey.

”In the Starsea Empire, everyone contributes in their own way.”

”Bulins and angels handle construction. Shipgirls, Spirits, and dragon girls handle combat. Loli scientists focus on developing new tech...”

”May I ask, ’Grey Tempest,’ what kinds of work you can or would like to do?”

The head maid asked very earnestly. She was genuinely curious what this nanobot could do.

Pfft—

Grey chuckled.

”I can do anything.”

”All types of work can be entrusted to me.”

”I can help manage planets or even a vassal world. I’m quite interested in organic societal structures.”

”If it’s scientific research... hmm, I’ve been in the L Cluster so long, I don’t know how far your tech has advanced. You’ll need to give me some time to get familiar with your empire’s current technological level.”

The learning capability of a nanobot was also astonishing. For an AI, photographic memory was just a basic function.

Her data analysis and synthesis abilities far surpassed any AI in existence.

In fact, as a civilization collective, there was no AI that could rival Grey.

”Can you turn into a Grey Goo fleet? How many ships could you make at most?”

Bismarck was more interested in Grey’s combat potential.

”Hold on!”

Grey shook her head.

”Let me clarify first: under most circumstances, I only fight in my singular unit form—the ship you saw earlier.”

”I can split into a fleet if necessary, but I can’t maintain a unified ’personality’ and consciousness at that range for long.”

Grey’s body was composed of countless nanobots, and splitting into a fleet essentially meant tearing herself into countless pieces.

Short-term control was fine, but long-term division interfered with her core awareness, risking loss of control.

”You can freely switch between humanoid and warship form... you really are like a shipgirl...”

”Wait, you even have a ground combat Gundam form? You’re basically a clone of the Commander?!”

Kayo Senju held her chin, studying the cute nanobot girl.

So this was why the Commander kept going on about her.

”Ho~~”

Grey drew out the sound, scrutinizing Setsuna.

”Commander, you have three transformation forms too? Looks like we’re kindred spirits, huh?”

...

After returning to the Solar System...

Setsuna took Grey on a tour of Earth and the Starbase, introducing her to the rest of the crew.

The nanobot needed only two days to understand the basics.

Her technological aptitude left even Kayo Senju and the other research lolis speechless.

Inside the research facility...

Grey observed the girls’ work at dizzying speed, occasionally nodding or shaking her head.

”Hmm... Hyperspace-based FTL engine research? No issues.”

”Neutron annihilation? Meteor Lance?! Oh, you people build wild weapons. I like it.”

”Photon spear? Your parameter setup is wrong, and the power design’s off. I’d recommend you actually understand the concept of photons before trying to weaponize them...”

Without using any support systems, Grey could calculate in an instant what would take regular AI days of simulation.

Even billion-scale data sets were trivial to her.

”By the way, you’re still working on retrofitting the Commander’s warship, right?”

Grey noticed one of the research projects.

Now that they had unlocked FTL tech, Setsuna and the shipgirls’ hulls needed a redesign.

The discovery of the L-Gate had come so suddenly that only basic retrofitting had been done before departure.

As for long-term upgrades, the lolis were still working on it.

”Yeah, we’re aiming to convert the Eternal Snowfall into a Titan-class, but the hull and weapon systems are still under design.”

Kayo Senju answered.

”No need to go through the trouble. I have a full database of ready-made designs.”

Grey opened a holographic interface and uploaded data to the control room computer.

There was so much of it, it almost crashed the server.

”Huh?!”

The lolis and shipgirls opened the files to find a vast collection of ship schematics.

The designs bore the distinct aesthetic of alien civilizations, ranging from corvettes to colossi.

They were incredibly detailed—not just blueprints, but full specs, production processes, and manufacturing notes. Bulins could probably build them straight away.

—The only downside was that all the text was in an alien language no one could read and would need translating.

There were also scattered advanced weapon techs.

Like terajoule-class kinetic cannons, gamma lasers, matter disassemblers, and more.

”What is this?...”

The research lolis’ eyes sparkled as if they’d discovered a treasure trove.

”This is some of the data left behind by the creators. You might find it useful.”

”Consider it spoils of war from the battle millions of years ago.”

Grey folded her arms and yawned.

”Though you’ll need to adapt the internal designs. Their species was quite different from yours—bigger bodies, extra heads, limbs, and tails.”

”...”

None of them could quite imagine what kind of bizarre beings had created the nanobot civilization.

But with Grey on their side, research progress would now skyrocket.

No tech in the Stellaris universe could block her.

”Titan... Titan...”

Kayo Senju sifted through the endless ship designs, hoping to find one suitable for modifying the Eternal Snowfall.

”Hmm?”

Suddenly, buried in the sea of schematics, she found something extraordinary.

Just the blueprint set alone was several times thicker than that of the Colossus. With matching parts and systems, it was easily the most complex design among them.

Compared to it, the Titan was but a toy.

[Juggernaut]

This gigantic structure was both warship and space station, composed of modular combat arrays and dockyards, dwarfing all standard capital ships.

The Juggernaut boasted enough firepower to wipe out entire fleets single-handedly and could build or repair vessels right at the front line, serving as a mobile base during offensive campaigns.

”A moving space fortress?!”

The research loli was stunned.

”Commander, I have a bold idea—”

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