Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Ah, if we’d known, we would’ve gone with the Commander too.”

After hearing about the Astral Express fleet’s experiences exploring several new worlds and getting acquainted with the newly arrived girls...

The shipgirls, Spirits, and others who had remained behind in the Starsea Empire’s homeland could not help sighing with envy.

Simply conquering a world was not necessarily all that difficult. With the Starsea Empire’s military might, most conventional worlds could simply be steamrolled.

But the very act of ”Trailblazing” was interesting in itself. After reaching space, adventure and exploration had practically become part of the Starsea Empire’s national ethos.

Seeing new worlds, meeting new people, encountering otherworldly magic and technology—exploring the unknown was always exciting.

—Except for the handful of lazybones who genuinely wanted nothing more than to lounge around the port and capital.

”Commander, which Astral Express are you taking next time? Bring me with you!”

Tohru rubbed against his shoulder and acted spoiled.

”Th-This... riding the Astral Express with the Commander and adventuring through other worlds is practically like a honeymoon! I want to go too!”

”You’re already thinking about next time?”

Setsuna laughed and rubbed her head.

”We’ll talk about it when we depart again. If you just want to go out and have fun, you can join one of the other crews. Elma’s crew could easily take a few more people.”

”Or we could just build a few more Astral Expresses.”

”Elma?! If I stayed with her all the time, we’d end up fighting! And I want to go with the Commander!!”

”...Fine, fine.”

Setsuna agreed.

Then, after everyone had gotten to know each other, they began settling the newcomers one world at a time.

”Ariel, Shiro, Wakaba Hiiro... the Bulins will open up a new residential area for you later. You’re free to do whatever you like within the Starsea Empire.”

”The otherworldly magic you control can enrich the Imperial Library’s collection. If you’re interested, you can also continue your studies at the Magic Academy.”

”All right.”

Ariel nodded.

”As for Sophia and those children...”

Setsuna thought about it. There were only a few adults from Kumoko’s world. Most of the others, including Vampy, were either infants or little girls.

”Shiro, you’ll serve as Vampy’s magic instructor. Everyone else will attend school together. Chen Hai, handle their enrollment.”

”Understood.”

”Huh? Me?!...”

Kumoko pointed at herself.

”Mm. I believe in you.”

Setsuna figured that if Kumoko had managed to train Vampy so thoroughly in the original story, then under the Starsea Empire’s conditions, she might be able to take things even further.

”Hehehe...”

Shiro took Sophia into her arms and chuckled a few times. Vampy suddenly had a terrible premonition.

”Yoshino, Lena, Koharu... you can do whatever you want. Ideally, continue attending school. Later, you can choose whether to pursue advanced studies in technology or magic.”

”Mako, keep training as well. There’ll be plenty of opportunities to learn ninjutsu and magic while exploring other worlds. Work hard and strive to become an outstanding anti-demon ninja.”

”Mr. Commander, what’s an anti-demon ninja?”

Mako Hitachi did not understand, but it sounded impressive.

”Ahem. A ninja who fights demons. I’ll teach you next time we encounter some during exploration.”

Setsuna cleared his throat.

”Oh...”

Mako imagined some heroic ninja wielding powerful swordsmanship and magic, gallantly battling demons, and found herself instinctively yearning for it.

”Chtholly, Nephren, you and the Leprechauns should go to the Life Sciences Department for comprehensive examinations. If necessary, you’ll all undergo genetic treatment.”

He then called Mobius and Ruan Mei over and entrusted the fairies to them.

”Come here.”

Ruan Mei beckoned Chtholly over, touched her chin with one hand, then lightly pressed several spots along her neck.

In an instant, she had grasped her genetic information and biological structure.

Narrowing her eyes, she thought for a moment.

”An incomplete form of life? Commander, they’re composed of fragments from some powerful existence. Strictly speaking, they can’t truly be considered living organisms.”

”Someone artificially created them through magic or something similar.”

”Smart. The Great Sage and the Poteau created them using necromancy. Their souls came from part of a Visitor—although the Visitors in that world aren’t what you’re thinking of.”

Setsuna teased Elq.

”Interesting.”

Ruan Mei thought for a moment.

”My research rarely touches upon the soul. Strengthening and repairing their physical bodies would be easy, but giving them independent and complete souls... interesting.”

”Come with me.”

She did not say much more. Having agreed, she gestured toward Chtholly.

”The techniques used by your creators were crude. They couldn’t solve the problems of biological decline and self-collapse. Since the Commander has entrusted you to me, while you’re in the Starsea Empire, I’ll do my best to make your lives... somewhat better.”

”Oh, all right. Thank you!”

Chtholly thought Ruan Mei seemed rather aloof, but perhaps she was actually a decent person?

Only Gudako and the others who knew the truth clicked their tongues and sighed.

”Sure enough, even the coldest genius becomes a little gentler toward someone brought in by her own Commander? Back in the day, you’d have been lucky if she didn’t dissect an alien for research.”

”Is this the power of something huge enough to make people submit?!”

”???”

...

After all the newly arrived girls had been settled...

The angels and shipgirls led them away in separate groups, arranging their residences in the capital according to Setsuna’s instructions and showing them around.

”This is the Starsea Empire’s residential district. Aside from the shipgirls, most people live here. If you need anything, contact an Angeloid.”

”Oh...”

In the past, the newcomers’ idea of a wealthy residential district amounted to little more than sprawling villa communities and estates. The Starsea Empire’s architecture, however, extended in every direction through three-dimensional space.

Mako looked upward. Many people’s homes floated in midair like hanging gardens.

The neighboring residences were arranged in carefully staggered layers, while holographic domes and anti-gravity systems ensured every building received proper lighting and remained perfectly stable.

Not far away was the Flügel residential area, where angels could be seen flapping their wings through the sky, giving the advanced cityscape a faintly dreamlike quality.

”Since you’re all ordinary humans for now, it’s better for you to live on the ground.”

”Once you’ve undergone superhuman modification or mastered flight magic, you can consider living higher up.”

Belfast assigned residences to them one by one and registered their personal identity information.

”You should already have learned at least a little about the Starsea Empire. There is no currency here. Food, clothing, housing, and transportation are all free. Take whatever you need.”

”Most reasonable requests will be fulfilled. If something requires too many resources, submit a request to the Commander or Yat Sen.”

”Oh!”

The new members felt like country bumpkins who had somehow wandered into Cybertron.

Especially after seeing the estate-sized villas and the household Angeloids assigned to each residence, they began wondering whether they were dreaming.

”Are we really allowed to live in a house this huge?! There’s no rent? We don’t have to work? And angels take care of daily life too? Whoa?!—”

”Spacecraft?! Everyone even gets their own spacecraft?! Ahhh!!!—”

Things that seemed perfectly ordinary to the Starsea Empire, benefits everyone had long since grown accustomed to, appeared unimaginably fantastical in the eyes of the newcomers.

Shiro, Mako, and the others forcibly restrained their excitement, feeling an overwhelming urge to throw their arms into the air and shout:

”What incredible kindness!!!”

”With this many benefits, I’d honestly feel embarrassed if I didn’t do something for the Commander.”

Chtholly spoke sincerely.

”Don’t worry. Remember when Yoshino asked earlier if there was anything you needed to pay attention to while living in the Starsea Empire?”

Gudako patted her chest and enthusiastically explained things to everyone:

”The Imperial laws were written by the Goddess of Justice, but under normal circumstances, you’ll barely ever need them. The crime rate here is zero. There’s basically no lawbreaking at all. The handful of troublemakers like Phantylia and Aura can only end up as helpless playthings.”

”If I had to give you one piece of advice... when the Commander invites you to a party, make sure you arrive on time.”

...

”Mm... ha!”

Early in the morning, inside the private residence on the top floor of the administrative center, Setsuna slowly opened his eyes and stared blankly at the transparent holographic dome for a while.

It was his first night back in the Starsea Empire, and he had slept extremely well.

The Astral Express fleet had not actually been away for very long, but perhaps because they had gone through several worlds in one trip, he somehow felt like a traveler finally returning home.

Here, he could completely relax without having to think about troublesome matters like conquering worlds.

Lying on the soft bed, his entire body loosened up.

”This is nice. I’ll sleep a little longer.”

”Zzz... Zzz...”

”Hm?!”

Wait, something seemed off.

Setsuna suddenly noticed the problem and looked down at the blanket covering him.

There was a human-shaped bulge in the lower half, and it was moving.

When he lifted the blanket, he saw exactly the person he expected.

”Kirie?!”

He jolted in surprise and looked at the silver-haired vampire girl.

Kirie was no longer wearing that complicated gothic dress. Instead, she had changed into a beige school uniform as casual clothing.

She had clearly gotten up very early and had already been ”working” for quite a while.

”What are you doing?”

”Eating breakfast!”

Kirie answered indistinctly, yet as though it were the most natural thing in the world.

”Commander, did you forget what you promised me?”

”I can’t drink blood in the Starsea Empire, so aren’t my cultivation and daily energy needs entirely dependent on you now?”

”You woke up so late. Honestly, I even had to help myself...”

She muttered complaints while continuing her work, looking both coquettish and adorable. Setsuna was genuinely impressed by the vampire’s enthusiasm.

”Besides, don’t you like this too? It woke up earlier than you did.”

As though playing a prank, Kirie flicked little Setsuna and looked at him teasingly.

”You’ve learned quite a lot, haven’t you?”

”Come here.”

Setsuna beckoned, and Kirie obediently crawled into his arms.

”What is it, Commander? Could it be that you’re feeling generous enough to let me drink some of your blood?”

The girl lightly bit his neck with the tips of her fangs.

”If that really won’t work, I can drink a little blood first to replenish my energy...”

”...”

Setsuna marveled at how this vampire became less proper by the day. Someone from an adult visual novel world really was different.

”Won’t work? Who are you saying won’t work?!”

He immediately decided to teach Kirie a lesson about proper conduct, and things only came to an end when the head maid began knocking at the door, preparing to come in and clean.

”Mm...”

At breakfast, little Cheshire, who was wolfing down her food, handed Kirie a pastry.

”A new recipe Momo Akanegakubo just made! It’s super delicious! Want one?”

”I’m full.”

Kirie rubbed her stomach.

She even felt a little indigested. She had eaten too much.

”?”

The little catgirl looked completely confused.

”Thieving cat...”

Taihou sniffed the air and cast Kirie a suspicious look.

”Ahem...”

”Commander, please mind the setting. Sometimes there are children here.”

Chen Hai cleared her throat.

After spending so long with Setsuna, she had seen plenty.

After a simple breakfast, Yat Sen presented the Starsea Empire’s work report from this period to Setsuna at the administrative center.

”This is the Empire’s development report for this period. Please review it.”

While the Commander was away, she, Richelieu, and Grey had temporarily handled most affairs.

All kinds of data were displayed clearly before him, summarizing both the Starsea Empire’s homeland and dozens of subordinate worlds.

This included population, technological development, newly explored star regions, production of various resources, and more.

Sophon’s statistics were absolutely precise, organizing the data from every world neatly into categories.

”Not bad.”

Setsuna flipped through the report and carefully examined the figures.

The homeland was undergoing large-scale cosmic development, while the subordinate worlds were steadily improving their technology.

The several universes newly explored by the Astral Express had already regained order under Sophon and the Angeloids.

Once a civilization’s development crossed a certain threshold, its rate of expansion changed from linear to exponential.

Over the years, relying on its practically limitless resources, the Starsea Empire had sent tens of millions, even hundreds of millions, of exploration units composed of Angeloids and Bulins into the universe.

They established outposts on unfamiliar planets, extracted resources, built colonies, manufactured more Angeloids and spacecraft, then headed even farther outward.

”The Starsea Empire’s exploration teams have now surveyed the entire Milky Way and will soon begin expanding into other galaxies.”

”In addition, advance teams have discovered the supermassive black hole at the galactic center. The Research Department has built an observation station in the nearby star region and is studying opportunities for further development.”

Sophon continued her report.

”The Engineering Department believes it may be possible to construct an unimaginably vast celestial-scale Galactic Wonder there.”

Looking down at the star map, the Milky Way appeared as a spiral disk formed from four major arms, with the Solar System located on the shorter Orion Arm.

The entire galactic disk slowly revolved around the galactic center. According to old data, the black hole there possessed a mass millions of times greater than the sun.

”You want to build a megastructure there?”

Setsuna smiled when he heard the key phrase.

”A Birch World or a Quasi-Stellar Obliterator?”

”Uh... you already know about those? They’re still only theoretical at the moment. The exact structure and technological requirements are still under research...”

Kayo Senju scratched her head.

”It’s fine. No rush. We have plenty of time.”

Setsuna laughed.

Among the many twentieth-century science-fiction concepts, aside from Freeman Dyson’s famous idea of surrounding a star with a Dyson Sphere to harvest its energy, there was another, less famous but wildly imaginative concept.

—Using a giant black hole as the core to create an artificial planet.

A shell world could be constructed around the galactic-center black hole, possessing land area equivalent to trillions of planetary surfaces while maintaining standard gravity.

Because of its immense scale, the world could easily support multiple nested layers of land like a spherical matryoshka doll, allowing it to house a nearly limitless population.

Named after its proposer, it could be called a Birch World, or translated more literally as a birch-tree world. Some game mods had even attempted to simulate what such a structure might look like.

”That’s so cool. Could we move to the galactic center in the future?”

Gudako listened with fascination.

”It really does sound more suitable as a capital than the Solar System. Uh, this place is a bit too remote... The center of the galaxy is where the core of an interstellar empire ought to be!”

It was foreseeable that, with the help of the Bulins, Angeloids, and various forms of magic, the Starsea Empire would rapidly expand beyond the galaxy in a relatively short period.

By then, the Solar System, this remote suburb of the Milky Way, might no longer seem worthy of being called the Imperial capital.

”Don’t rush things. We’ll take it slowly.”

Setsuna tapped her on the head.

There was no one else in this universe competing with him for territory anyway, so they could expand steadily and securely.

”Expand the forward bases there as soon as possible. Reassign a few Bulin fleets to assist them, and continue expanding our development of this universe.”

”Yes!—”

”Our nation is thriving!”

...

Setsuna spent some time processing and reviewing the work report.

The Empire’s territory was vast, but Sophon’s administrative efficiency was extremely high, and most trivial matters could be handled within the subordinate worlds themselves.

As a result, there were actually very few matters that required his personal decision.

”Commander, do you have any plans for today?”

Yat Sen poured him a cup of tea and asked.

”Mm...”

Setsuna thought for a moment.

He looked out over the bustling capital in the distance.

”Since I’m finally home, I’ll make a round of inspections... then maybe we can all do something everyone enjoys?”

—

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