Crossover Shipgirls: Building a Dimensional Empire from Scratch

”You can think of it as us having some additional means of observation beyond this world.”

Setsuna casually made up an excuse.

Fu Hua remained half-skeptical.

The other party knew her inside and out—even about the Thirteen Flame-Chasers, her travels across Shenzhou, and the Fireseed Project.

Yet she knew nothing about him.

The feeling was unsettling.

Setsuna could tell what was on her mind.

So, with the aid of a holographic projection, he gave Fu Hua a rough explanation of his side.

”The Honkai world you are in is part of the Trea and Sea system. And the Trea and Sea universe itself is part of the greater multiverse…”

”My universe is right next to yours. We’re basically neighbors. Look—this is the Starsea Empire.”

Shwoosh—

The projection displayed a thriving capital cityscape, leaving Fu Hua momentarily dazed.

The Previous Civilization.

No, it was a world even more prosperous than the Previous Civilization.

Mega-cities stretched for thousands of kilometers, buildings rising from the earth all the way to the heavens.

Angeloids soared through the skies, while starships traversed the stars.

Even the Previous Civilization, destroyed by the Final Herrscher, had never reached such heights.

This was a galaxy-spanning interstellar empire, fundamentally different from surface-bound civilizations.

Let alone here, where civilization had only just emerged a few thousand years ago, not even close to modern society.

Fu Hua’s comprehension was exceptional. With Setsuna’s explanation, she quickly grasped the situation.

”You come from another world? No wonder…”

”For civilization to develop to this degree—there wasn’t any Honkai outbreak?”

”Cangxuan (Fuxi) and Dan Zhu (Nuwa) merely passed on knowledge beyond their era and triggered judgment-level Honkai beasts. But you…”

She stopped mid-sentence, realizing her line of thought had led to a foolish question.

”In our universe, Honkai doesn’t exist. The Starsea Empire’s tech tree follows Stellaris + Three-Body + Azur Lane.”

Setsuna chuckled.

”The magic side relies on the Spirits, dragon girls, and Type-Moon Heroic Spirits creating their own system. Honkai can’t exactly cross worlds to enforce itself, right?”

”How wonderful.”

Fu Hua sighed sincerely.

A world without Honkai, where civilization could flourish without fear of constant calamities, Honkai beasts, or Herrschers.

Truly enviable.

If the Previous Civilization had not been destroyed by the Final Herrscher, could fifty thousand years later it have also become a mighty interstellar civilization like the Starsea Empire?

Instead of what it had become now—struggling for survival through one Honkai after another?

The thought came to Fu Hua unbidden.

After a few words of admiration, she confirmed that Setsuna’s group indeed bore no hostility.

Though the claim of being from another universe was bizarre, their sincerity could not be faked.

After pondering briefly, she looked at Setsuna.

”Then may I ask, what is your purpose in coming here?”

”….”

”What year is it now?”

Setsuna asked casually.

”Year 1475 of the Common Era. The Ming dynasty’s current emperor should be the Chenghua Emperor?”

Yat Sen activated her ship equipment, scanning the surroundings.

”Hmm, though it looks like this civilization is advancing faster than the normal historical line—likely due to some guidance?”

The development of the Common Era had relied heavily on the Flame-Chasers’ legacy, leading to rapid evolution beyond the norm.

”….”

Setsuna fell into thought.

The Honkai world’s timeline was awkwardly wedged in between—

Neither fully Current Era nor fully Previous Era. For now, meeting Elysia or Kiana was out of reach.

But looking at it positively, there were still things he could do in this timeline.

In the original story, Fu Hua would soon be betrayed by seven disciples, losing most of her power and immortality.

To protect Shenzhou, she had been forced into a deal with Otto, becoming one of his Valkyries.

That could never be allowed to happen again.

Fu Hua was Fu Hua. The price she paid to later become Squad Leader Fu Hua was far too cruel.

Besides, wasn’t there also supposed to be a certain pink-haired fox waiting in the Far East for him to rescue?

And then there was the Schicksal Legion’s eastern expedition, along with a series of butterfly effects it triggered…

Setsuna quickly reviewed the current world situation in his mind, following the timeline.

”Are we going to fully conquer this world?”

Seeing Setsuna deep in thought, Tohru asked.

”This world’s overall strength isn’t high. We should be able to take it quickly.”

The dragon girl stated what was natural to the Starsea Empire.

”?”

Fu Hua glanced at Tohru and Setsuna, her expression complex and incredulous.

World conquest… a term common among ancient emperors.

She had seen many who bore such ambition, wanting to build eternal empires.

They led armies to sweep across continents, seeking to conquer all within their sight.

But no one had ever truly succeeded. And as the protector of Shenzhou, she could not allow outsiders to invade its land.

The rulers of Shenzhou, bound by the limits of feudal technology, neither had the ability nor the will to conquer the world.

Yet these visitors from the stars seemed to be seriously discussing it.

As if conquering other worlds was routine for them.

”No.”

Setsuna thought for a moment.

”We’ll save full conquest for later. For now, our approach to this world will be primarily observation and research.”

”Have Grey send some Bulin and research lolis over here. Build an observation station in Earth’s orbit to study this world’s Honkai Energy and its natives.”

”Also, besides microcosmos research, the science division should focus on technology related to mathematical laws.”

”Try constructing a mathematical model of the Honkai universe. I’ll provide relevant data. The difficulty should be lower than back home.”

It was foreseeable that, due to his presence, the Honkai world’s plot would be drastically rewritten.

If certain people disappeared because of changes to the timeline, that would be a huge loss.

To ensure the outcomes he wanted—to make sure the right people appeared when they should—

Setsuna considered using an advanced technology he had just learned from the Zero-Homer: Mathematical Law Weapons.

By building a complete mathematical model of the universe, he could simulate and manipulate its development.

The Zero-Homer could deduce the fate of civilizations trillions of years into the future, and the universe’s end itself. Setsuna didn’t need that level of complexity.

Just simulating the Honkai world’s direction was enough. He had plenty of reference material for the research lolis.

When the Honkai universe’s mathematical model was complete, he would clearly see every person’s fate within it, and alter them at the right time.

This was also a chance to study and wield a Law Weapon.

”Understood.”

At Starbase, inside the research building, a nanobot who had been working at a desk looked at the message, stood up, and clapped its hands.

The research lolis all turned their heads.

”Alright everyone, pack your bags. Bring along Bulin and the Angeloids.”

”We’re heading to another world again. This time, we’ve got a new mission: observing the natives.”

”Hooray!!”

The little girls cheered excitedly.

”???”

Fu Hua was dumbfounded.

Law Weapons? Observing natives?

What was he talking about? Why couldn’t she understand any of this?!

”Could you explain more clearly? What exactly do you plan to do with this world—and with Shenzhou?”

Out of a strong sense of duty, she stared at Setsuna and asked.

”….”

”In simple terms, this Earth hasn’t mastered faster-than-light travel, nor has it built starships. It’s still a primitive civilization.”

”For such primitive civilizations with research value, we generally construct an orbital observation station and observe the natives.”

Setsuna explained.

”Of course, we’ll also conduct experiments related to Honkai Energy—it is, after all, this world’s unique trait.”

”?”

Fu Hua froze.

”You… how exactly do you observe them?”

She pressed further.

”Well…”

Setsuna opened a holographic document titled Space Sociology II: Observation Rules for Primitive Civilizations, and began explaining:

”For pre-space-era primitive natives, the Empire currently has several observation methods: passive observation, active research, indoctrination, and technological enlightenment.”

”Passive observation means keeping a safe distance and studying them without their knowledge. Active research involves abducting or luring locals to study them more directly.”

”Indoctrination is using various means to align native thought and ideology with ours.”

”As for technological enlightenment—that’s helping natives rapidly advance to the space age, then integrating them as our vassals.”

Setsuna explained each one to Fu Hua.

”Given the existence of Honkai Energy here, we won’t conduct technological enlightenment for now. So, we’ll mainly use passive research.”

”….”

Fu Hua stared blankly at the holographic display.

She noticed that the textbook even said: Produced by Starsea Empire Starfleet Academy (Authors: Chen Hai, Hai Tien).

What was this?

Building an orbital station to monitor Earth? Studying Honkai natives?

She had never seen or heard of anything like it.

I don’t understand, but I’m deeply shocked.jpg

Am I being treated as a native too?!

Fu Hua—questioning life itself.

She had walked the lands of Shenzhou for countless years, revered by the people as its protector, and recognized in the martial world for centuries as the foremost master.

Even emperors had to address her as ”Immortal” with reverence and respect.

Through thousands of years, she had witnessed joys and sorrows, dynasties rising and falling.

No matter the situation, Fu Hua’s heart had long been still as water—nothing could stir ripples within her.

Years of experience had forged a detached and tranquil disposition, allowing her to view the world from a higher vantage point.

But this scene—she had never seen before.

An interstellar empire? Observing natives?

What kind of nonsense was this?!

”You… no, wait…”

Fu Hua struggled to find the words, rare for her to lose composure.

Here, in the Common Era, she was confronted with a super-civilization whose technological level far surpassed even the Previous Era.

”No rush. Take your time. I’ll answer your questions as best I can.”

Setsuna leaned back in his chair, smiling at her.

”Observation, and then what? You said you wanted to research Honkai—then what is your goal?”

After calming herself, Fu Hua asked.

”My plan is to find a way to recruit this universe’s Herrschers and Valkyries, and form two special forces units alongside the shipgirls, Spirits, and Heroic Spirits.”

”Once that’s accomplished, this world will be annexed into the Starsea Empire, and governed by the Empire.”

”Of course, before that, I’ll eliminate the threat of Honkai, and ensure that under the Empire’s rule, the civilians here will enjoy better living conditions.”

Setsuna replied.

”???”

If not for the fact that the man before her radiated steady energy and spoke with logical clarity—

If not for the fact that his earlier words, though bizarre, still carried a consistent logic—

Fu Hua would have thought he was a lunatic who had gone astray in cultivation, or was suffering from severe delusions.

Recruiting Herrschers?

Valkyries?!

Why did he act as though defeating Honkai was such a simple matter?!

And what in the heavens were Heroic Spirits and shipgirls?!

There were too many absurdities; Fu Hua didn’t even know which to question first.

In all her thousands of years of cultivation, this was the first time her mind felt like it had crashed.

Seeing her incredulous expression—

Setsuna stood, patting Fu Hua lightly on the shoulder.

”In that case, Immortal—”

”Come. See with me the world beyond Earth. The era has changed.”

...

A few minutes later—

Shwoosh—

Fu Hua followed Setsuna onto a small shuttle.

Even from the perspective of the Previous Era, the shuttle’s structure was advanced.

She didn’t know why she had agreed to Setsuna’s request.

Perhaps curiosity, or perhaps responsibility.

When faced with such a strange visitor from beyond the stars, as Shenzhou’s guardian, she had to understand his true nature.

”Master?”

Just as they were about to lift off, a young woman with long black hair in ancient attire hurried over.

Drawn by the commotion in the mountains, she gazed in astonishment at the ship before her.

”Return.”

Fu Hua waved her hand.

The young woman froze for a moment, then did not move further.

”Oh, your good disciple, huh.”

Setsuna clicked his tongue.

No matter the excuses, Fu Hua’s seven disciples conspiring to murder their master was undeniably heinous.

According to the timeline… it should happen next year?

But now that he was here, who knew what the future would become.

Fu Hua didn’t notice the implication in his words.

She simply nodded lightly.

”My first disciple, Lin Zhaoyu. She has been with me the longest, and to the others, she is like a second teacher.”

”tsk…”

Hum—

The shuttle’s thrusters roared to life, breaking through the atmosphere, into outer space.

”….”

Fu Hua gazed through the window at the vast sea of stars, thoughtful.

She recalled her final battle with the Final Herrscher. It had been far too long since she last stepped into the starry skies.

”Speaking of which, I always wanted to learn Edge of Taixuan.”

Setsuna said casually.

”In the early days, when I first went to the Demon Slayer world, I seized a bunch of breathing techniques and sword arts. Back then, I thought—these aren’t very interesting to practice. If only I could learn Edge of Taixuan, that would be better.”

”If I’d known you were here, I would have contacted you sooner. Maybe conquering some of the later worlds would’ve been easier.”

”Oh?”

Fu Hua didn’t quite understand what ”Demon Slayer world” was, but she could tell that the man before her had a genuine interest in Edge of Taixuan.

That was her signature art, and aside from a few disciples, few even knew of its existence.

She carefully studied the man in front of her.

”The best time to temper the sword heart is in youth—the earlier, the purer. Adults cultivating the sword heart is like trying to grasp the wind with your palm—futile.”

”Have you studied the sword?”

”Mm… I guess I’ve learned a bit of ahoge swordsmanship?”

Setsuna drew Excalibur, giving it a flourish.

Spoils from the Second Singularity—not something he used often.

He had sparred a bit with Artoria, but he didn’t know the names of the moves. So, he just made one up.

”Ahoge swordsmanship?”

Fu Hua shook her head, thinking the name was rather odd.

She observed him more seriously.

”Your swordplay seems unpolished. You haven’t practiced much, have you?”

”Your breathing is steady, your talent is good. With proper practice, grasping divine essence may not be difficult…”

She cut herself short halfway.

Though his potential was high, he was not her disciple. There was no need to say too much.

”No worries. For me, practicing swordsmanship is just to add skill points and keep fit.”

”In most cases, I don’t need the sword—it’s too inefficient, and its power too limited.”

Setsuna sheathed the blade.

”Hm?”

”Inefficient…?”

Fu Hua’s brow furrowed.

As they spoke, the shuttle broke free of Earth’s orbit.

Judging the distance sufficient—

Setsuna extended his hand.

Shwoosh—

The colossal form of the Eternal Snowfall was projected into the void.

Fu Hua felt as if an immense giant had appeared before her.

It stretched thousands of kilometers in length, wings of armor casting darkness over the stars. Looking up, she could only see endless arrays of turrets and missile silos.

Starlight streaked across its metallic hull in silver bands. The longer one stared, the more it induced vertigo.

”Wh-What is this?!”

Fu Hua’s heart quaked.

When they had once fought the Final Herrscher on the moon, this vessel was even larger than the moon itself.

”The Eternal Snowfall—my ship-body. You can think of it as something similar to Project Bunny. No… you probably haven’t seen Project Bunny yet…”

Setsuna thought for a moment, then explained it in terms Fu Hua might understand.

”Projecting a warship from nothing?!”

Fu Hua was even more stunned.

The shuttle ascended, landing within the vast command bridge.

The futuristic arrangement filled Fu Hua with wonder and awe.

”Hua, as you see, this is the flagship of the Starsea Empire—and a part of me: the Eternal Snowfall.”

Setsuna stood at the main console, turning around, with the sea of stars behind him as he spoke calmly.

”The Eternal Snowfall is armed with one Fallen Star Lance, one hundred and twenty positron lances, one hundred and twenty-eight photon particle cannons, and sixteen thousand medium-range artillery.”

”The underside houses six massive hangars and one neutron eradication device—capable of wiping out planetary civilizations without damaging structures. Had the Final Herrscher swept Earth with neutron eradication back then, no one in the shelters would have survived.”

”The Fallen Star Lance can, within a ten-thousandth of a second, reduce the moon to molecules—or shatter the sun. At full firepower, I can extinguish an entire star cluster in an hour.”

”If necessary, I can also deploy dimensional-reduction weapons—dual-vector foils. No three-dimensional lifeform can escape being flattened.”

Finishing, he looked sincerely at Fu Hua.

”I came to help you resolve the Honkai crisis. I believe this level of force should be enough.”

”….”

Fu Hua remained silent for a while. She was, indeed, shaken by this pinnacle of technology.

Resolve the Honkai crisis?

Now she felt that Earth itself was in crisis.

—

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