Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Tsk, our world-conquest progress is going rather smoothly, huh.”

Shuaa—

Opening the Hyperdimensional Star Map, Setsuna checked on nearby neighbors as well as his personal notes.

He crossed off the Azur Lane world mission.

Initially, he had planned to follow Compiler’s suggestion—to study the technology of traversing parallel universes in order to retrieve the Arbiters.

Unexpectedly, their initiative was far greater than he imagined. Relying on spatial beacons, they returned on their own.

They even brought along several pieces of Siren-related technology, which the META division had already begun researching.

Once their research results in the field of spatial mechanics were integrated into the Imperial database, it would surely bring new breakthroughs to the Research Department.

”So, next up...”

”We’re continuing with the next world conquest?”

Setsuna glanced at the star map.

[Neon Genesis Evangelion]

A classic mecha series from the early era. The story takes place in the early 21st century, when Earth faces a new type of invader—a race of giant, human-shaped mechanical beings called Angels.

The Angels were once thought to be divine messengers sent by God to destroy humanity for its sins. At that time, all of Earth’s conventional weapons—every tank, missile, and nuclear device—proved useless against them.

In response, the nations of the world united, establishing NERV (the Human Instrumentality Committee) and poured vast resources into creating a new kind of weapon—one controlled directly through the pilot’s neural link.

The Evangelion units.

Although called mecha, the Evas were more like bioengineered weapons than machines.

Naturally, the world of Evangelion is deeply intertwined with Christian symbology—and revolves around the grand ambition of turning all humanity into orange juice through the Human Instrumentality Project.

It bore a curious resemblance to the VIRM assimilation plan between Klaxosaurs and humans in the DARLING in the FRANXX world.

”I think if I take the Strelitzia, I could solo an Angel easily. This world doesn’t look that hard.”

Gudako leaned in curiously.

After its interstellar refit, the Strelitzia was equipped with compact Tachyon Lances, Corrosive Missiles, and all sorts of advanced weaponry.

If necessary, it could even enter its True Apus form. With such overwhelming technological superiority, its combat power far surpassed that of any Evangelion unit.

”Hmm, true. Not that hard. That Earth could even make a decent vassal world...”

”I’ll go! I’ll go! I’ll go—!”

Gudako shoved herself next to Setsuna, eyes gleaming with excitement.

”Last time in the Re:Zero world, beating up the locals wasn’t that fun. This time, let me try a proper mecha world for once!”

”You, old lady, should just do what you always do—float around in orbit, eat popcorn, and watch the show. I promise to complete the mission, thrash the locals, and spread the glory of the Starsea Empire across the world—”

Thump—

”Who are you calling old, huh?”

Setsuna lightly bonked her on the head.

While the two were bickering—

Suddenly.

Beep—

A communication signal came through.

A holographic interface opened in front of them.

”Good day, Mr. Setsuna. How have you been recently?”

A familiar voice, a familiar greeting—coming from Chaldea.

Da Vinci smiled warmly as she watched Gudako playfully sparring with Setsuna.

”Oh, I hope I’m not interrupting anything?”

”Nope!”

Ritsuka Fujimaru straightened her clothes and sat up properly.

”Are you... in outer space right now?”

Romani noticed that behind them was a Starbase—and beneath it, a blazing sun.

”Yeah. The Starsea Empire is currently constructing a Wonder. I’ll be stationed here for a while.”

Setsuna replied calmly.

”A Wonder?...”

”You mean like the Statue of Zeus, the Pyramids, or the Hanging Gardens?”

Da Vinci blinked in amazement.

In some of their records, certain Heroic Spirits possessed powers connected to Wonders.

”No, it’s a Galactic Wonder—something built across stars and planets.”

”A-A-A what???—”

The two fell into brief confusion, unable to process what they’d just heard.

Every time they contacted the Starsea Empire, they ended up shocked beyond words.

From starships to faster-than-light travel, and now to Galactic Wonders—Romani no longer dared imagine what the next call would bring.

”So you contacted me... does that mean you’ve located the singularity?”

Setsuna asked succinctly.

”Yes, we have.”

After taking a moment to compose himself, Romani answered.

”This time, it’s the Fifth Singularity. The timeline is 1783, location—North America.”

”Small problem.”

Setsuna yawned.

Given the Starsea Empire’s overwhelming power, all remaining Singularities—including the Grand Temple of Time—could easily be steamrolled.

Reconstructing Human Order was more like a formality at this point—an excuse to recruit a few more Heroic Spirits along the way.

”So, what’s the plan? You going solo this time, or should I tag along?”

He turned to Gudako. Since he’d promised Chaldea to restore Human Order, he intended to do it properly.

”I’ll handle it myself! If you send the Eternal Snowfall to bombard everything from orbit, what else would there be left for me to do but watch?!”

Gudako raised her hand without hesitation.

She’d taken care of the Fourth Singularity on her own before, and her confidence was sky-high.

”By the way, if you’re assigning me companions this time, send fewer shipgirls. Their firepower’s so ridiculous, I barely got to play last time.”

”...You’re seriously trying to negotiate terms with me?”

Setsuna pinched her cheek lightly.

Shuaa—

He pulled up the Fifth Singularity’s data.

The plot was simple: in 1783, North America had fallen into civil war. One side mass-produced soldiers using the Holy Grail, while the other mass-produced robots through ”science.”

The United States had turned into a Divided States.

As usual, the task was to retrieve the Grail and fix the Singularity’s bug.

”Hmm... no real challenge. Just charge straight through.”

Setsuna thought for a bit. He was more interested in the Sacred Round Table territory or the Absolute Demonic Front, so he’d leave this one to Gudako.

”I don’t need to tell you which Heroic Spirits to bring back, right? Nightingale, Helena... wait, Scáthach’s there too? And Bride Nero?!”

He noticed several particularly intriguing Servants.

A purple-haired old hag—or rather, purple-haired anti-demon ninja... no, the Queen of the Land of Shadows.

Long purple hair, skintight outfit, and a massive heart—right up Setsuna’s alley.

And in terms of combat power, Scáthach ranked near the top among Heroic Spirits.

As for Nero... the Fifth Singularity featured her Bride form, but he had already pulled one from the Second Singularity.

Who knew what kind of chaos would happen if there were two Neros at once.

”Tsk... am I helping you find wives or restoring Human Order here...”

Gudako smacked her lips.

”That’s just how Chaldea works—the Commander just has to—”

”Stop right there.”

Setsuna cut her off mid-chant.

He opened the comms and selected a few companions for the mission.

”Elma, New Jersey, Essex... and Pandora. You’re all going with her.”

Since it was the North American Singularity, it made sense to send the Eagle Union shipgirls. The dragon girl would provide overwhelming suppression power, and the Witch of Vanity was strong enough to offer solid backup.

”Alright...”

Pandora, who had been bored wandering around the capital, thought a trip to a real alternate world sounded fun.

”Oh, right! Commander, leave the Evangelion world to me!”

Before departing, Gudako waved frantically at Setsuna.

”I’ll be back soon! I’m taking the Strelitzia to beat up the locals! Wait for me, okay!!! Don’t go without me!!!—”

”...You really don’t know when to stop, do you?”

...

Before long, the five arrived in Chaldea.

”This is the dragon girl—she went with me last time...”

”These are the Eagle Union shipgirls, and this one’s the Witch of Vanity...”

Gudako introduced her companions one by one, while Romani and Da Vinci looked on in astonishment.

”A witch?! What’s next, a magical girl?”

”Magical girls would be overkill for Chaldea, thanks...”

[Anti-Summon System: Activated!]

[Initiating Spiritron Transfer—]

[Spiritron Transfer begins in...]

”5... 4... 3... 2... 1...”

[All systems complete!]

[Fifth Singularity: North American Mythic War]

A flash of white light—and in the blink of an eye, they found themselves standing in a foreign wilderness.

Rumble—

Boom—

Not far away, a raging battlefield stretched before them.

Mechanized soldiers and classical-era warriors clashed in a chaotic, surreal spectacle—a mix of absurdity and postmodernism.

”Oh... interesting.”

Pandora, still thrilled by the sensation of interdimensional travel, eagerly examined the strange surroundings.

Essex and New Jersey manifested their hulls, and immediately, the entire battlefield was cast under the shadow of their starships.

An overwhelming swarm of carrier-based aircraft launched into the air, followed by Angeloids descending in formation, quickly pacifying the chaos below.

”Suppress the world, resolve the Singularity, and secure the Servants we need. Move fast.”

”Estimated operation time... two days? Too short? Fine—three days! No more than that!!!”

...

After sending off Gudako to handle the Singularity, Setsuna shifted his attention back to the Hyperdimensional Star Map.

With the Evangelion world already reserved, most of their neighboring worlds had been dealt with.

It was time to explore further across the star map—to see if there were any new potential targets for conquest.

Shuaa—

He poured his psychic energy into the star map, dispersing the fog that shrouded its edges.

At this point, locating and opening up worlds across the multiverse was merely a matter of time—and perhaps a little mental fatigue—for him.

Soon enough.

Far beyond the current borders of the Starsea Empire, five new civilizations appeared marked on the map.

In Stellaris terms, these weren’t exactly ”neighbors” anymore—being separated by multiple intervening worlds.

[No Game No Life – Tier-III Magic Age]

[Nyaruko: Crawling with Love – Tier-IV Magic Age]

[A Certain Magical Index – Tier-IV Magic Age]

[Tengen Toppa Gurren Lagann – Space Age]

[Problem Children Are Coming from Another World – Tier-V Magic Age]

”...”

”Huh???”

Setsuna blinked, momentarily stunned.

”Tsk...”

”This is... high-difficulty content?!!”

Not long ago, after spotting the Flügel and Ex-Machina species entries in the Codex, Setsuna had already suspected that the No Game No Life world was within observational range.

So its appearance wasn’t too surprising.

As for the other worlds—well, ever since he had chosen Galactic Nemesis and Cosmogenesis as his Ascension Perks, the system had warned him:

”Farther within the grand multiverse, you will encounter new worlds of ever-greater challenge.”

And indeed, challenge was putting it lightly.

Each world was a heavyweight in its own right.

”I knew it—there’s no such thing as a free Aetherophasic Engine or Horizon Needle... figures.”

Previously, the highest magical civilization level he’d seen on the star map was the Goblin Slayer world—classified as a Tier-III Magic Age.

Now the map directly listed IV and even Tier-V Magic worlds.

Setsuna wasn’t entirely sure how the star map determined these classifications, but it was obvious that these were far more extreme than anything before.

[No Game No Life]

He’d looked into this world before. Essentially, it was an isekai where countless races decided everything through so-called ”games.”

The God of Games possessed the authority to erase and recreate the entire world.

The most valuable resources of this world were, of course, its various races—Flügel, Ex-Machina, Dragonia, and others—perfect for enriching the Starsea Empire’s biodiversity.

And, of course, the Suniaster, symbol of absolute dominion.

Conquering this world would require careful planning.

Next, his gaze moved to the remaining worlds.

[A Certain Magical Index]

This series was also one he knew well.

In the Academy City of Japan, a large population of students possessed supernatural abilities, ranked from Level 0 (no ability) to Level 5 (super ability).

In addition to basic education, schools there conducted research to enhance and evolve these powers, driving intense competition among students.

Their abilities were incredibly diverse—ranging from teleportation, hydrokinesis, and psychokinesis to exotic powers like vector manipulation and electrokinesis.

But beyond the Academy City and its espers, what truly mattered in this world were the global religious organizations—and the existence of beings known as Magic Gods.

He skimmed the world summary for A Certain Magical Index.

[A Certain Magical Index – Tier-IV Magic Age]

This world contained beings who could influence and interfere with the world’s laws—the Magic Gods.

A complete Magic God could command all principles of reality, manipulating the very ”phases” of existence. Through these, they could destroy and recreate worlds from nothing.

”...”

Now that was a real Magic God—able to twist rules and reshape reality with a mere thought.

Far beyond the so-called ”Demon Kings” shoved into dungeon worlds like Goblin Slayer or Konosuba.

Eliminating the Magic Gods aside, flattening the rest of Academy City’s world wouldn’t take long.

But to completely conquer it, that was another story entirely.

And beside Index, two equally insane worlds awaited...

[Tengen Toppa Gurren Lagann] and [Problem Children Are Coming from Another World]

The former was an early-era mecha anime set in an alternate futuristic world, centered around a force known as Spiral Power—the power of evolution.

This energy was infinite. Any lifeform possessing spiral genes, or any galaxy with a spiral structure, could infinitely expand by drawing upon its ascending spiral energy.

The race that mastered the power of evolution was known as the Spiral Race.

Meanwhile, to suppress evolution and limit other spiral species, there existed the Anti-Spiral Race.

Both sides waged war by creating fleets and ”faces”—massive mecha—for battle.

The defining feature of the Gurren Lagann universe was its mecha scale, which became so absurd in the later stages that it defied comprehension.

The Super Tengen Toppa Gurren Lagann stood hundreds of billions of light-years tall, treating galaxies like frisbees and planets like grains of dust.

In a sense, it represented the ultimate endpoint of mecha technology.

”Uh... strong is strong, but also kinda weird?”

Setsuna thought that adapting to Spiral Power wouldn’t be difficult for him—but piloting a supercluster-sized mecha just felt... bizarre.

[Problem Children Are Coming from Another World]

Also known as the Little Garden.

A world so overloaded with settings it could make one’s head spin.

Being labeled as a Tier-V Magic World said enough about its level of power.

Setsuna compared the Index, Little Garden, and Gurren Lagann worlds.

Then he glanced again at the Puella Magi Madoka Magica world he’d discovered earlier.

”...”

Insane. Every single one of them.

All top-tier worlds.

Conquering any of these worlds couldn’t be done the usual way—by simply sending a fleet and auto-attacking everything in sight. Careful planning was essential.

The higher the risk, the greater the reward.

If he managed to conquer all of them, the Starsea Empire would undoubtedly become a true multiversal empire—one uniting the technologies and magics of infinite worlds.

He even felt a bold idea stirring within his heart.

Authority War Between Worlds.

The victor would seize all resources and divine authorities of the target world.

The Starsea Empire had already fought two such cross-world wars.

The first, experimental in nature, had won them a trove of Teigu from the Akame ga Kill world.

The second had yielded numerous world-class items from the Overlord world—along with the YGGDRASIL game authority, allowing him to literally design new characters at will.

Weak worlds offered little of value. Beating them down only meant having to rebuild them later. Setsuna had been waiting for the right moment.

According to the ability’s description, its ultimate purpose was Authority Seizure.

If one’s own strength was sufficient—strong enough to defeat a world’s ”God” or ”Magic God”—then he could directly usurp their authority.

To gather the powers of all gods into one.

—Assuming he could actually win the war without getting coin-dropped by the other side.

”Tsk, this won’t be easy...”

Setsuna rubbed his chin.

Warring against gods wasn’t the same as beating up locals. He’d need to plan thoroughly and act only when the timing was perfect.

Finally, he turned his attention to one rather peculiar world.

[Nyaruko: Crawling with Love]

Its tone was quite different from the others—more like a slice-of-life comedy.

It told the story of a girl named Nyaruko who came to Earth under orders to protect an ordinary high school student.

As everyone knew, comedy characters were often the strongest.

Nyaruko looked like a silver-haired, green-eyed girl—but her true form was Nyarlathotep, an Outer God from the Cthulhu Mythos.

In that world, most of the girls were either aliens or star-spawn—practically none were actual humans.

Earth there was considered an undeveloped planet, with humans viewed as a primitive species under protection.

”If a Cthulhu looks like a beautiful girl, feels like a beautiful girl, and sleeps like a beautiful girl—then she is a beautiful girl.”

Setsuna figured it was time to expand and update his XP system.

Besides humans, shipgirls, dragon girls, and Spirits, there was no reason Outer Gods couldn’t count too.

”I want my Cthulhu waifu too!!!”

—

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