Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Now that everything here is settled, how about coming with me to take a look at the Starsea Empire?”

Setsuna reached out and pinched Astrologos’ cheek.

”Eh!”

The little girl was caught off guard and hurriedly stepped back two paces, clutching her chest.

”You mean… you want me to offer myself as compensation and follow you to another world?”

”My, my~ Commander, you’re tricking girls again~”

Elysia rested her chin on her hand, watching the show.

”You help a girl save her country, then ask her to repay you with her body. Tsk~”

”...”

Astrologos’ gaze circled around Setsuna several times.

Though they hadn’t known each other long, she was filled with curiosity about this team from another world.

Whether it was Kiana—who looked exactly like the Second Prince—or the unbelievable flying ship and all sorts of miraculous magic, everything seemed fascinating.

But she still shook her head stubbornly.

”No.”

”You have your world. I have my empire.”

”Though Huodou has been eliminated, the realm is far from peaceful. Those who covet the throne still lurk in the shadows. If I simply walk away now, Emberya will fall into chaos.”

Her tone was firm, nothing like her petite and delicate appearance.

”I must remain here and continue fulfilling my duty.”

”Is that so? Fair enough. That’s the Astrologos I know.”

Setsuna smiled and lightly tapped her forehead.

”M-Mr. Assassin, you—you—what are you saying? And why do you keep taking liberties with me?!”

Astrologos covered her head, her face flushed red.

”But what if I told you that this world cannot exist for long? That in the future, Emberya will be destroyed along with this bubble world?”

Setsuna said casually.

”What…?”

Whoosh—

Cosmic Juggernaut accelerated high above the sky.

The entire world’s landscape spread out beneath them. The continental structure here was completely different from Earth’s.

In this world, which had never developed technologies like airplanes or trains, Astrologos had never seen her nation from above, nor had she traveled very far due to technological limitations.

Now, gazing at the scenery below, she was filled with wonder.

”Tell me—what do you think the universe looks like? How big is it?”

Setsuna asked.

”The universe?…”

Astrologos looked confused.

”In other words, the world.”

”Mm… The heavens are round and the earth is square? The sky is like a dome covering the land? As for its size…”

She pondered for a moment before giving an unsurprising answer.

”At the borders of Emberya lies the edge of the world. The sky should be slightly larger than the land, so it can encompass this continent?”

”Pfft hahaha—so you really are from ancient times.”

Kiana nearly burst out laughing.

”No, no, the universe isn’t like that. Let me explain… Bronya, see? There are people dumber than me after all.”

”Listen carefully, Miss Astrologos. Earth is within the solar system. If we calculate by the range of its gravitational well, the diameter of the solar system is about four light-years. And the diameter of our observable universe is…”

”A light-year? It’s the distance light travels in one year. Ah—right, you don’t even know that concept yet…”

She opened a holographic interface and began earnestly giving Astrologos a crash course in the Starsea Empire’s astronomy.

Setsuna waved a hand.

”No. In this bubble world, what Astrologos said is actually correct. This universe is indeed very small.”

”Huh?!”

The white-haired girl puffed her cheeks in disbelief.

”The Emberya—or rather, the world of Honkai Kingdoms—is essentially just a bubble world within the Sea of Quanta.”

Setsuna spoke slowly.

”If we regard the Honkai world we come from as the original world, then the other bubble worlds are merely its shadows.”

”The sizes of bubble worlds vary. An original-world level possesses an eternal future, unaffected by the Sea of Quanta, and can even sustain the existence of Honkai itself.”

”The smallest, bubble-level and artificial worlds can only loop within a single event. They are extremely unstable. Once their mass is exhausted, they dissipate.”

”Bubble worlds maintain dynamic balance by continuously absorbing external energy. Smaller ones, if insufficiently stable, can easily collapse inward into spacetime fragments, eventually decaying into wreckage at the bottom of the Sea of Quanta.”

Buzz—

Cosmic Juggernaut sped toward the boundary of the sky.

”When we first arrived in this bubble world, did you notice something?”

”We didn’t enter outer space first and then descend onto this planet.”

”Instead, we appeared directly above Emberya.”

Setsuna asked.

”That’s true!”

Kiana suddenly realized.

”Before, we always arrived in outer space and then descended into planetary orbit. Why was it different this time?…”

”Because this bubble world is only this big.”

Setsuna gazed out the viewing window.

BOOM!!—

In just a few minutes, the accelerated Cosmic Juggernaut reached the outside of the world.

Beyond the ship, the scenery once again transformed into the boundless Sea of Quanta, countless blurred bubble worlds drifting within it.

”There is no Milky Way, no galaxy clusters, no universe spanning billions of light-years. The Emberya and its continent are everything this bubble world contains.”

”Beyond the bubble world lies the Sea of Quanta. Of course, without Cosmic Juggernaut, no one here could ever break through the world’s boundary in their lifetime.”

”Ah…”

For a moment, everyone felt slightly dazed.

They recalled the miniature universe they had once obtained from the Three-Body world. The state of a bubble world was quite similar.

Not every bubble world contains trillions of stars and a vast cosmos. On the scale of interstellar civilizations, many are quite small.

A single star system. One planet. Even a short segment of looping, severed time—any of these could be a bubble world.

Its entire world might be only that large.

”Mm…”

Astrologos was stunned by the structure of the Sea of Quanta. It took her a long while to regain her senses.

”So this is what lies beyond the world?”

With zero knowledge of Honkai or the Tree and Sea system, she struggled to comprehend Setsuna’s explanation.

She could only rely on the educational materials displayed on the holographic interface and Sophon’s explanations to grasp fragments of it.

For those living inside a bubble world, nothing appears abnormal. They simply accept it as the rules of the world.

But once one steps outside, their perspective changes instantly.

”Yes. The bubble world you inhabit isn’t large, nor is it particularly small. It barely manages to maintain its existence within the Sea of Quanta.”

”If the influence of the Sea of Quanta and the world’s decay cannot be resolved, one day it will sink to the bottom like the others.”

Setsuna pointed ahead.

At the depths of the Sea of Quanta lay countless shattered bubble worlds.

From their wreckage, faint fragments of their former spacetime could still be seen.

”Th-this…”

Astrologos felt flustered.

When facing Huodou or other exotic beasts, she could rely on her knowledge to set up formations and resolve the crisis.

But now, with the fate of an entire world laid before her—even with all her intelligence—she was at a loss.

Instinctively, she didn’t want to believe Setsuna’s words, yet her intuition told her they were true.

Whether it was the Imaginary Tree or the Sea of Quanta, these were existences she had never seen or heard of before.

”...”

Astrologos tugged at Setsuna’s sleeve.

”Mr. Assassin… please help me. Tell me what I should do next.”

”I… I cannot stand by and watch Emberya be destroyed.”

”Well, that’s simple enough.”

Setsuna cleared his throat.

He tapped the main console, and the AI projected a standardized contract.

”Sign this agreement. From now on, you’ll be citizens of the Starsea Empire.”

”Under the Empire’s protection, we’ll naturally help you resolve every crisis.”

”Eh?”

Astrologos subtly realized that Setsuna seemed to be tempting her into signing something suspiciously similar to a treaty of national subjugation.

”Y-You… you mean for Emberya to exist under the Starsea Empire from now on?”

”How could that possibly be acceptable?!”

”The technology to anchor a bubble world isn’t difficult for us. Smaller bubble worlds can attach themselves to other worlds and survive dependently.”

Setsuna gestured for Astrologos to sit down and poured her a cup of tea.

”The Starsea Empire will provide you with a certain degree of technological support. As it happens, projects like developing bubble worlds would definitely interest MEI, Tesla, and Vill-V.”

”For you and for Emberya, this is the best option.”

A bubble world of this scale did not possess many exploitable resources.

However, as a research sample for studying the Imaginary Tree and the Sea of Quanta, it was quite valuable. Since they had encountered it, they might as well take it along.

”Eh…”

Astrologos’ mind felt completely muddled.

They had only just met. Setsuna had first helped her eliminate Huodou, then immediately proposed vassalization. It was obvious he was speedrunning the entire world.

She simply couldn’t keep up with his pace.

After lowering her head to think for a long time, she finally looked up.

”I… I cannot directly agree to your terms.”

”If I were to hand Emberya over to outsiders just like that, I would have no way to answer to the late emperor or to my subjects.”

”Mr. Assassin, I would like to visit the Starsea Empire first and see whether it is truly as formidable as you claim. Then I will make my decision. Is that acceptable?”

”Of course.”

Setsuna agreed readily.

...

A short while later.

Whoosh—

Cosmic Juggernaut descended near the imperial palace of Huangyue City.

”Wha—?!”

The civil and military officials below, along with the palace guards, were thoroughly startled.

They had been searching everywhere for Astrologos’ whereabouts. The moment they looked up, they were met with a colossal starship blotting out the sky.

”Who goes there?!”

A girl with shoulder-length hair and dressed in a luxurious qipao was the first to rush forward with the guards, surrounding the landing site.

”Oh? Isn’t that Rita?”

Those aboard the ship watched with interest.

In this bubble world, she was the Prime Minister of Emberya and Astrologos’ right-hand aide.

”It’s me~.”

Astrologos descended in a shuttle. With a light thump, she landed neatly on the ground.

”Your Majesty? Where have you been?! Today is your official day of ascension to the throne. Why did you suddenly flee the palace?”

”There are already rumors spreading throughout Huangyue City. Some even say Your Majesty has been harmed by assassins. Fortunately, fortunately…”

As she spoke, Rita’s gaze shifted toward Cosmic Juggernaut and the group behind Astrologos.

”Your Majesty, these people are?…”

”Ahem. It’s a long story.”

Astrologos waved her feather fan lightly.

”Following the late emperor’s guidance, I was searching for a method to seal the ancient exotic beast Huodou when I happened to encounter Mr. Assassin… ah, no, the Commander.”

”He told me certain astonishing things. In short, I must travel far for a time. During my absence, the affairs of Emberya will be entrusted to you.”

Astrologos did not elaborate in detail. She did not wish to cause unnecessary alarm.

”???”

Rita blinked, utterly bewildered.

”Your Majesty, although Emberya is currently at peace and free of war, you have only just inherited the throne. Is it truly appropriate to leave the nation for a distant journey?”

”This matter is extremely important, Rita. I trust you can manage Emberya well. During this period, all matters of state will be decided by you.”

Astrologos’ tone was resolute.

”If any unexpected situation arises…”

”Here. Use this to contact us.”

Setsuna tossed a terminal device to Rita.

”Sophon will also remain stationed in this world. Simply address the sky, and you will receive a response.”

”Hah?!”

Rita felt as though she were listening to myth.

Yet seeing that Astrologos had no intention of changing her mind, she could only fall silent.

Soon after.

Astrologos summoned the equally confused officials of Emberya and, in the form of an imperial edict, formally entrusted the nation to Rita for the time being.

Then she waved to the crowd and boarded Cosmic Juggernaut.

”Until we meet again.”

...

Whoosh—

Cosmic Juggernaut activated once more.

Space twisted violently around them as the ship sped toward the distant horizon.

Before long, it broke through the boundary of the bubble world and returned to the Sea of Quanta.

”Wow…”

Kiana, Mei, and Elysia gathered around Astrologos, teasing her playfully.

Though she had yet to meet her counterpart in this world and was only nominally visiting the Starsea Empire for ”inspection,” experience suggested that every native who arrived in the Empire ultimately found bliss here and forgot all about returning—losing themselves in the utopian life of the interstellar age.

”So cute. Aunt Theresa would definitely be shocked if she saw you…”

The white-haired girl attempted to rub Astrologos’ head, only to have her dodge decisively.

”Theresa? Who is Theresa? Why do you keep mentioning her?”

”She’s the principal of the Valkyrie Academy… Well, you two are basically the same person, aren’t you?!”

”Oh my… so the Commander has tricked another girl into coming back with him~?”

Elysia rested her chin on her hand and asked teasingly.

”Commander, are you planning to travel from bubble world to bubble world, collecting girls and bringing them all back to the Starsea Empire?”

”And you’ve discovered my plan?”

Setsuna snorted lightly.

”Hmm… Let me think. There are still quite a few people to ’fish up’ from various bubble worlds. Perhaps we should bring Luna back as well? Three Theresas together—sounds rather nice.”

”???”

Elysia had absolutely no idea what he was talking about.

”But before that, let’s handle proper business. This trip is for testing Cosmic Juggernaut and searching for another parallel universe. As for developing bubble worlds, we can take our time after returning.”

Beep—

He glanced at the bubble world coordinates Edison had previously given him. Honkai Kingdoms was only one of them. There were others waiting to be explored.

[Coordinate calculation complete. Sophon network detected.]

Accompanied by the AI’s prompt, he locked onto another bubble world.

Boom!!—

After passing through a kaleidoscopic spacetime tunnel, another starry sky unfolded before them.

On Earth below, crowds bustled about. Angeloids moved back and forth maintaining order, no different from the previously conquered Current Era civilization.

[Sophon Unit 26 greets you.]

[During the 75 standard hours since physical connection was lost, all conditions in this world have remained normal. One transport route is currently obstructed and will resume once a teleportation anchor is established.]

The Sophon responsible for managing this world manifested as a projection and nodded respectfully to Setsuna.

”Whoa—are we home?!”

Raiden Mei and Bronya hurried to the viewing window.

The scene below was identical to the Earth they had left. Ordinary people had no idea they had been shifted into a parallel universe.

They continued living and working as usual.

Sophon thoughtfully connected them to their homes, allowing them to exchange a few simple greetings.

”Phew—”

Seeing it with their own eyes, the last weight in their hearts finally lifted.

”How incredible… The Previous Era and the Current Era will now develop in parallel? People from fifty thousand years ago and fifty thousand years later existing together?…”

”Commander, I want to go down and take a look~”

Elysia poked Setsuna.

”Go ahead. From now on, this is all part of the Starsea Empire.”

Setsuna took out a teleportation anchor and fixed it within the starry sky.

”Let’s go home.”

—

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