Crossover Shipgirls: Building a Dimensional Empire from Scratch

After roughly finishing the story of their Trisolaran journey to their stationed companions—

It was time for the most exciting part: tallying up the spoils.

They had spent a long time in the Trisolaran world, and from the Trisolarans, the Singer, the Zero-Homers, and other civilizations of varying levels, they had reaped all sorts of things.

”Here, first up are the things from the Trisolarans.”

”We obtained sophon-manufacturing technology, along with a few other miscellaneous gadgets.”

Kayo Senju projected some data onto the holographic screen.

”The droplets were merely probes, useless to us. Our tachyon sensors can instantly scan the surrounding star regions, so we’ll skip that.”

”Sophon, however, is a microscopic particle created by the Trisolarans. It can extract energy from the vacuum, travel at speeds extremely close to light, and use quantum entanglement to achieve instantaneous communication.”

”It can also enter anywhere through microscopic higher-dimensional space, and freely switch its own dimensional state.”

From the perspective of the Starsea Empire, the Trisolarans were just sub-light natives they could crush at will.

Their tech tree, too, was quite skewed.

They could manufacture higher-dimensional sophons, two-dimensionalize them, etch circuits into them as supercomputers, and then fold them back into microscopic eleven-dimensional form.

When it came to dimensional science and technology, the Starsea Empire was still largely blank.

”Isn’t that the thing they used to lock down human science? What can we do with sophons?”

Tohru tilted her head.

”Sophon itself is also a highly advanced artificial intelligence. It can simultaneously process billions of threads, while monitoring the movements of an entire planet.”

”All of its reasoning and calculations are based purely on logic and data analysis, unaffected by emotional interference. It is the perfect assistant tool.”

Setsuna thought for a moment.

”We can assign them to govern our vassal worlds.”

”Oh yes!!!”

”Glory to science!!!”

The shipgirls immediately cheered.

The Starsea Empire had more than a dozen vassal worlds. Normally, shipgirls took turns stationed there to manage them.

Although the natives of the vassal states were always respectful toward their suzerain and never dared to cause trouble—

It was still another world away. Staying there for months at a time without seeing the Commander was boring.

Most shipgirls weren’t very interested in ruling worlds anyway. They preferred to stay by the Commander’s side.

Now, sophons could free them from such duties.

From a ruler’s perspective, sophons were even more suitable than shipgirls, since they could monitor an entire world’s movements in real time.

In their eyes, no secret could be hidden.

”Mhm, a super AI? Sounds kind of like Grey?”

Everyone looked at the nanobot girl, noticing some similarities.

”Please. I can beat Zero-Homers and local natives into calling Commander ’Daddy.’ Can sophons do that?!”

Grey scoffed.

She insisted she was the pinnacle of artificial intelligence technology.

”Next are the things seized from the Singer’s ship.”

The little loli continued.

”Photoids and dual-vector foils.”

”Mhm, photoids were already used to refit the shipgirls over there. Now the expedition fleet all has photoid launchers. From this day forward, we officially have rapid star-destroying capabilities.”

”Dual-vector foils are far too dangerous. They are strictly forbidden in our home universe and vassal worlds. Except for a few being used in Trisolaran space for research, all are kept under the Commander’s custody.”

Setsuna nodded.

”If there’s ever a need to use them, you’ll have to come to me for approval.”

”Also, stationed shipgirls should have Bulins install photoid launchers for you. Same goes for Kancolle and Arpeggio—these things are simple in principle, and easy to retrofit.”

”Ohhh!!!”

Several little shipgirls manifested their rigging, proudly showing off their newly installed photoid launchers to the others, who looked on enviously.

”Last month we even held a star-shooting contest!”

A little blue-haired shipgirl wearing a tiger-head hat bragged to the stationed Spirits and dragon girls.

”Sister Tai Yuan hit three stars, Sister Fu Shun hit five, Tashkent hit four… but me? I hit six!!!”

”Hmph, that last shot was mine—it’ll hit thirty years later! The Commander said so, I’ll definitely hit it!!!”

Fu Shun was unwilling to concede, arguing with Chang Chun over who had actually hit more stars with photoids.

”If it’s not now, then it’s not a hit!”

”Thirty years later counts! The Commander said so!”

”What if it gets intercepted?”

”Impossible!!”

”…”

Everyone else listened with black lines on their faces.

”Good grief!! You girls go out once, and now your idea of fun is shooting suns?!”

The Heroic Spirits were dumbfounded by the destroyer shipgirls’ casual chatter.

These tiny destroyers, usually treated like children—Nero, Jeanne d’Arc, Jeanne Alter, and others often played with them in their spare time.

Now, they wielded weapons capable of destroying stars and even wrecking entire star systems.

Compared to that, Noble Phantasms like Excalibur, Golden Theater, or Jeanne Alter’s curses suddenly seemed trivial.

Kurumi Tokisaki glanced out the porthole at the sun, tugged on Setsuna’s sleeve, and hesitated:

”Um, Setsuna-kun, I do hope you’ll show some restraint here?”

”After all, unlike shipgirls, I can’t survive in outer space with just my body, let alone fly FTL.”

”We won’t!!”

Chang Chun and Fu Shun solemnly swore.

”The Commander said anyone who plays with photoids in this universe will get spanked. Absolutely not!!!”

”Oh?”

”Really? Spanked by the Commander? That’s… such a scary punishment… maybe I should give it a try.”

Chapayev manifested her rigging as she spoke, eyeing the star map for a target.

”I’ll do it.”

Richelieu flexed her silk-gloved hands with a cold expression.

”…Never mind.”

The others who had been tempted immediately lost interest.

At last, they came to the greatest harvest of the trip.

The data obtained from the Zero-Homers…

”Mhm, I skimmed through what they sent over…”

”In terms of basic science, we don’t need it. Our Stellaris-era science far surpasses that of the Zero-Homers’ alliance.”

”But when it comes to matters involving universal laws, we believe there’s great application value.”

The research lolis and a few Sirens listed out a report.

Two items were marked as most important:

[Pocket-Universe Creation Technology] and [Mathematical Laws].

”We’ve already heard the Zero-Homers explain mathematical laws. By constructing mathematical models, they can deduce everything that happens in the universe.”

”And guide all things to develop according to their will.”

”Unfortunately, their sub-light mathematical models don’t apply to us. We’ll need to rework them under our own universe’s rules.”

Kayo Senju added.

”That way, we too will have foresight of the future, and even abilities akin to manipulating causality.”

”Hiss—”

Everyone shivered.

Foresight of the future. Manipulation of causality.

Such abilities were no longer just weapons, but abstract concepts.

Just hearing the names was enough to know these powers were utterly absurd.

The thought of two civilizations, each mastering mathematical laws and causality manipulation, going to war—it was enough to make one’s head ache.

”As for pocket-universes, they appeared later in the third volume of Trisolaris.”

”They’re expansions of the greater universe, with independent constants and timeflows—a bubble cosmos isolated from the main one.”

Setsuna continued.

”Er… you can think of them as miniature pocket-worlds, with parameters you can set however you like.”

In the later Trisolaran era, when the greater universe faced destruction, many civilizations built pocket-universes to try to escape annihilation.

Inside, they waited for the main universe to cycle back to singularity, and return to the pastoral age.

But taking too much matter from the main cosmos created new problems.

Cheng Xin’s choice to return the pocket-universe in the end was wise, though leaving behind only a five-kilogram biosphere was… puzzling.

”Can we build one?”

A small shipgirl asked.

”Yes. But it will take considerable resources. We could start small, as a test.”

Setsuna considered.

”Independent time outside the greater cosmos?”

Gudako caught on immediately.

”So that means… we could also adjust the flow of time inside the pocket-universe?”

”Of course.”

Setsuna gave her a strange look.

”So that means… inside a pocket-universe, you could… drive the Eternal Snowfall silver—”

Whack—

Before she could finish, a sharp hand-chop landed on her head.

”Is your brain filled with nothing but trashy thoughts?!”

”Wait, you’re lecturing me?!”

...

At the shipgirls’ strong insistence, the first Trisolaran technology to be put into use was the sophon.

The Bulins spent a week constructing a giant particle accelerator in Earth’s orbit.

The construction techniques came from the sophon itself, which had once been used to monitor Earth.

After the Trisolarans were wiped out, Nymph obtained control of that sophon, which carried with it a portion of Trisolaran technical data, and promptly handed it over to Setsuna.

The blueprints and schematics were all written in Trisolaran script. The research lolis had considered studying and translating them further—

But the Bulins claimed they understood it just fine.

So Setsuna gave the order, and the project immediately went into motion.

”This time we’ll use high-energy collisions to trigger reaction, producing thirty protons, then unfold them into two dimensions and etch in supercomputer circuits.”

”If all goes well, we’ll manufacture thirty sophons.”

On an open plain outside the capital, Kayo Senju proudly reported the progress to Setsuna.

One sophon was enough to govern an entire world. Considering the growing number of vassal worlds to manage, they decided to produce several at once.

As the Empire’s borders expanded, sophons could even be promoted to sector governors, managing multiple star systems or nebulae.

”Mhm, begin.”

Setsuna nodded.

”Activate the particle accelerator, bruin!!”

With a Bulin’s command, the massive, city-sized, oddly-shaped particle accelerator in Earth’s orbit roared to life.

High-energy particles were accelerated to near-light speed within its tubes, colliding to briefly distort the fabric of space.

Overhead, the starry sky twisted into bizarre graffiti.

”What’s happening?”

The shipgirls, watching curiously, looked up.

”Sophon exists in eleven dimensions. When unfolded into higher dimensions, what we see in three-dimensional space is only its projection.”

”It’s like how a two-dimensional being could never perceive the whole of three-dimensional reality—only its projection on a flat plane.”

Kayo Senju explained.

”Oh…”

The crowd half-understood.

It was hard to imagine that just a few years ago, these same little lolis were starving and shivering. Now they stood at the forefront of the Starsea Empire’s research.

They had conquered light-speed, surpassed it with FTL, and now they were advancing toward dimensional science.

The anomalies in the sky lasted only a few minutes before the lolis in the space station began unfolding the sophons into two dimensions.

The Starsea Empire’s technology was far more advanced—there would be no blunders like the Trisolarans’ early sophon experiments, which created the so-called Magic Eye civilization.

A thin, dimensionless plane was spread out in the cosmos, draping itself over Earth under the pull of gravity.

Then, countless Bulins manifested their rigging, each wielding their meow-meow hammers, and set to work upon the two-dimensional sophon.

They etched circuits into it, shaping it into a supercomputer.

By now, the research lolis and shipgirls had long since stopped questioning how Bulins could use hammers larger than themselves to inscribe nano-, femto-, and even yoctometer-scale circuits.

If the Bulins said it worked, then it worked.

If it couldn’t be built, they would simply reply: ”That’s not Bulin’s job.”

Such was the chaotic might of Azur Lane’s magic, and the very foundation of the Starsea Empire.

A few days later, the first sophon was complete.

It reverted to three-dimensional form, becoming an invisible fundamental particle, hovering over Earth’s North Pole.

[Sophon-2 ready. Awaiting orders.]

A holographic display opened before Setsuna, accompanied by a cool, clear female voice.

”Stand by.”

Setsuna gave the concise order.

In the following days, under the Bulins’ tireless hammering—

The particle accelerator continuously produced protons, unfolded them into two dimensions, and etched circuits.

They returned to three-dimensional form as fundamental particles.

What the Trisolarans had labored with all their might to create as a singular super-intelligence, the Starsea Empire could now mass-produce.

Five days later, all thirty sophons were completed.

[Sophon Unit Two ready]

[Sophon Unit Three ready]

[Sophon Unit Four…]

On the holographic interface before Setsuna, the sophons were neatly listed by number.

Counting the one captured in the Trisolaran universe that was still monitoring humanity there, the total came to thirty-one.

”Wait—just sending them to govern vassal worlds, is that really appropriate?”

”Humans can’t even interact with sophons, right? Or is Commander planning to completely block their science?”

Formidable blinked, realizing a problem.

Sophons were invisible to humans. They could monitor an entire world, but their ability to directly intervene in the material world was weak.

Responding to sudden incidents might be troublesome.

”Didn’t the Trisolarans already show us how to solve that?”

Setsuna smiled and clapped his hands.

Shwoom—

Several rows of metal stasis pods were carried over by the Angeloids.

Inside each pod lay a girl.

They had delicate, oriental-style features, dressed in dark kimonos with hairpins adorning their heads.

Pale-skinned, eyes closed, they rested silently.

”???”

”Don’t tell me… this is…”

The shipgirls were stunned.

”Dolls?”

Gudako blurted out.

”Commander, Commander… I didn’t expect you to be dissatisfied even with shipgirls, making toys for yourself instead? Tsk, tsk…”

Whack—

Setsuna smacked her on the head.

”These are for the sophons! They’ll control humanoid robots!!!”

He had faithfully recreated the appearance of sophons from the Trisolaris story, crafting them physical bodies.

Having a form would make things far more convenient.

”Each sophon controls one.”

Setsuna ordered via the holographic interface.

”Understood.”

Thirty sophons descended from Earth’s orbit.

From invisible higher-dimensional states, they entered the robots’ bodies and immediately took over their control systems.

”…”

Two neat rows of identical girls slowly stood up, bowing gently toward Setsuna.

”Sophon at your service, my Lord.”

Their movements were graceful, their expressions calm, carrying a faint air of nobility.

In any human world, they would undoubtedly turn every head on the street.

”Sophon Units Two and Three, remain in the administrative center to assist with this world’s management.”

”The rest of you—govern the vassal worlds.”

Setsuna swiftly assigned them their respective jurisdictions.

Each sophon’s computational power could easily manage an entire planet. With their humanoid bodies, crafted with Angeloid technology, they could also suppress rebellious natives if necessary.

Information flowed instantly between all sophons, and from the Eternal Snowfall’s mainframe, their status could be monitored in real time.

”Understood.”

...

Across the vassal worlds—

Shipgirls stationed in administrative centers looked with surprise at the sophons who had arrived to take over.

Even after multiple upgrades had greatly enhanced their abilities, they had to admit that expertise mattered.

As advanced AIs, sophons could grasp every aspect of a world’s state in an instant.

Production, population, industry, agriculture, pollution—nothing escaped them.

Photographic memory was merely a basic function.

From the data alone, they could generate complex development plans that no one else could even understand.

At the same time, no disturbance in the vassal worlds could slip past their eyes.

It was no exaggeration to say that if you asked a sophon how many grains of rice a person had eaten for lunch yesterday, it could answer immediately.

”Zzz… this is great. With sophons helping, I don’t have to do any work anymore…”

In the Akame ga Kill world, Indomitable tidied up her belongings.

Yawning, she prepared to return to the port area to sleep.

”Stay in your room forever, why don’t you.”

Formidable said casually while combing her hair before the mirror.

”Tonight the Commander’s holding a celebration on the Eternal Snowfall for the triumphant return. He’s even going to use temporal distortion authority to give us a one-month vacation.”

”Indomitable, care to guess which Illustrious-class carrier wasn’t invited?”

”???”

The black-haired, green-eyed shipgirl jolted with a shiver.

”No way! You’ve got to take me this time!!!”

—

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