Crossover Shipgirls: Building a Dimensional Empire from Scratch

While the Spirit squad conquered the Elves, other teams were also waging campaigns across Disboard.

Each unit chose opponents best suited to them, approaching first with diplomacy, then with power—bringing the entire No Game No Life world a firsthand experience of extraterrestrial civilization.

Far across the great ocean, deep beneath the waves—

A magnificent underwater city lay hidden in the depths.

Its scale rivaled that of any major surface metropolis, its architecture elegant and refined.

The ones who traversed this city were all beautiful young women.

Their skin was smooth and fair, their faces breathtakingly lovely, adorned with gold and metallic jewelry. Yet, from the thighs down, their bodies were covered in glimmering scales, their feet resembling fins.

The Seiren—the fifteenth-ranked race among the sixteen—were a people who could only survive in the ocean’s depths.

They cared little for, nor were they aware of, the affairs on land.

During the great wars, their unique environment kept them safe—too remote and too uninteresting for the higher races like the Dragonia, Flügel, or Gigants to bother with.

Most Seiren only knew how to play, living carefree lives beneath the sea.

”Hmm…”

In the heart of the grand city of Oceando stood the royal palace of the Seiren Queen.

A woman whose beauty surpassed that of all her kind gazed thoughtfully at a map before her.

”The Starsea Empire? Conquering the world?”

”Whatever… no one’s going to bother us anyway…”

A nearby Seiren girl drifted lazily beside her, completely unconcerned.

No matter how fierce the wars raged on land, the higher races paid no mind to those living in the ocean depths.

Self-sufficient thanks to abundant marine resources, the Seiren had no reason to interact with the surface.

Thus, the sudden appearance of new conquerors stirred more curiosity than fear.

”But if they truly seek to rule the world, they won’t overlook us…”

The Seiren Queen’s expression grew uneasy.

”It’s fine! We’re under the sea—no way their ships can come down here.”

Another cheerful Seiren flicked her tail with a laugh.

”Unless they’re like the Flügel and can split the ocean itself—but that’s impossible, right?…”

”Let’s take a look.”

With that—

A small group of Seiren flicked their fins and swam upward, breaking through the surface.

They peered up at the starships hovering above.

”...”

”Oh? All girls? Are those mermaids?”

The shipgirls watching from above were intrigued.

The Seiren did, in fact, look remarkably similar to the mermaids from fairy tales.

”See? Their ships can’t come down.”

The Seiren girls exchanged smug looks with the shipgirls above.

A few mischievous ones even made faces at them.

”Bleh, bleh, bleh~~—”

”???”

Formidable raised an eyebrow, question marks practically floating over her head. She realized the ones below were just a bunch of playful brats.

”They’re an aquatic race! And kinda cute. Let’s go say hi!”

Beside her, a dozen lightly dressed shipgirls eagerly volunteered.

”Mhm.”

With permission granted, they dove into the sea.

”Wah—they jumped in! Don’t drown out here!!—”

The Seiren girls gasped in surprise.

”Iona, ready. I-400, I-402—deploy hulls.”

”Archerfish, Dace—entering the water.”

The submarine shipgirls materialized their vessels mid-air.

Massive starships, tens of kilometers long, crashed into the waves, sending towering walls of water surging skyward.

”Phew… haven’t been underwater since the space era. Kinda nostalgic…”

Clatter—clatter—

In an instant—

A vast deep-sea-and-space hybrid fleet emerged across the ocean’s surface.

”Eh?!”

”What is that??!”

The onlooking Seiren were dumbfounded—the sheer size of each vessel rivaled their entire underwater cities.

The weapons onboard were unlike anything they had ever seen.

They had always felt safe in the ocean’s depths, but now…

”Hi there! I’m Bluegill. Mind if we talk?”

A blonde, blue-eyed, adorable submarine shipgirl poked her head out from the cockpit.

”Don’t be afraid, we’re here to—”

Before she could finish—

”Ahhhhhhh—!!”

”Fish! Giant fish! Bluegill!!—”

The Seiren collectively panicked and fled toward Oceando in chaos.

”Hmph. Weak species.”

Esdeath leapt down from the ship.

The instant her boots touched the ocean surface, the Herrscher of Ice’s authority activated.

Crackle—

Frozen ice rapidly spread, forming a glacial path from the sea toward Oceando.

Amidst the terrified gazes of the Seiren, she stood before their queen, her tone icy and commanding.

”Surrender to the Starsea Empire—or else… hmph.”

With a mere wave of her hand, vast regions of the seabed froze solid. None of the Seiren doubted that this terrifying woman could freeze the entire ocean if she so desired.

”Waaaah…”

The Seiren Queen nearly burst into tears.

They were never a combative race—and facing both ice magic and submarines, they had clearly met their natural nemesis.

”If we surrender… there won’t be war?”

”Of course.”

Esdeath raised an eyebrow.

”As long as you abide by the Starsea Empire’s laws, you’ll be allowed to live freely. However, your leader must accompany me to pledge loyalty to the Commander.”

”Uu…”

The Queen hesitated.

”That’s fine, but… there’s one small issue…”

”Speak.”

”Our race consists solely of females. We must breed with other species to sustain our next generation. Within the Starsea Empire… is that permitted?”

”???”

Esdeath, expecting a fight, almost lost her breath.

”What the hell?!”

”Oh, right…”

Tesla smacked her forehead.

”I remember reading the records—the Seiren aren’t skilled at fighting. Their special trait allows the spirits within their bodies to attract those of other lifeforms, like a natural seduction or charm ability.”

”It’s said that coupling with a Seiren brings ecstasy like ascending to heaven… though the partner usually ends up drained of life and spirit.”

”What?!”

Esdeath choked.

”What are they, succubi?!”

Thinking for a moment, she opened a comm link to Setsuna.

”Commander, reporting—the Seiren have surrendered without resistance and wish to join the Starsea Empire. However, there’s… a unique circumstance.”

”What? Heavenly pleasure? I don’t buy it. Bring a few back for testing—I’ll observe personally.”

Grey replied casually.

”If it’s true, we can always replicate their biology later—give the Commander a proper treat.”

”Deal!”

The Seiren girls eagerly surrounded them.

”Me, me, me! I’ve never met a male from another race—let me go!”

”Me toooo~!”

”???”

The Ice General, Esdeath, was completely dumbfounded.

...

Elsewhere—

The Angeloids were carrying out a detailed surface scan.

Among the ruins of an ancient battlefield—

Ikaros, Nymph, and Astraea moved carefully through the wreckage, following their sensor readings.

Whoosh—

Suddenly, a small figure flashed before them.

A girl, appearing around ten years old, stood before the Angeloid unit.

She had long crimson hair—her beauty almost unreal—but parts of her body were clearly mechanical.

Her slender frame was wrapped in a simple linen tunic, two mechanical conduits extending from her back, their crystalline tips flickering with light.

Flash—

The mechanical girl suddenly lunged at Ikaros, moving far faster than any human could react.

Clang!

Ikaros caught her easily with one hand.

”Eh? Who’s this kid?…”

Nymph paused mid-snack, blinking.

”Analyzing—unregistered species detected.”

The girl tilted her head, speaking in a flat, mechanical tone.

”Processing… evaluating situation…”

Bzzt—

Streams of complex data and code flickered within her amber eyes.

”Analysis: target identified as mechanical lifeform. Not part of network collective.”

”Error—cannot parse—error…”

She emitted a string of error codes.

”This unit—designation Üc207Pr4f57t9—query: identify yourselves.”

”Yo, isn’t that Schwi?” The moment she recognized the girl, Nymph grinned.

She was, after all, the heroine of No Game No Life: Zero.

”Schwi?... No record found for that designation.”

”Correction—this unit is individual Üc207Pr4f57t9. Query: identify yourselves.”

The girl replied in an emotionless mechanical tone.

”This is the First Expeditionary Force of the Starsea Empire. We’ve come under orders from Master to find you.”

Ikaros answered seriously.

”Confirmation: no record found for said civilization name.”

”No hostility detected. Terminating attack intent.”

Schwi retracted her deployed armaments and tilted her head upward.

”Query: who is this Master? What is the purpose of your search for this unit?”

”...”

Her flat, procedural way of speaking made the Angeloids’ processors ache.

Though Ikaros, Nymph, and Astraea were also mechanical beings, their thoughts were clearly far livelier.

”Hey, what are you doing here, anyway?”

Finding her cute, Astraea leaned in and patted Schwi’s head.

”Wow, your material’s pretty advanced—but not quite realistic enough.”

”...”

”Response: this unit has been investigating the concept of a ’heart.’ During analysis, logical errors occurred repeatedly, resulting in deactivation. Post-deactivation, this unit continued individual observation.”

Schwi spoke without a hint of emotion.

The Ex-Machina—an advanced race of mechanical beings functioning as a Gestalt civilization.

Each mechanical body was part of a single networked entity, transmitting all received data back to the central command core.

Thoughts were shared in real time, decisions made collectively, loyalty absolute. To provoke one Ex-Machina was to provoke the entire race.

Thus, though ranked tenth among the sixteen races, few dared to provoke them.

If any individual malfunctioned, the command core could sever its link—effectively declaring it defunct.

Just like the little girl before them.

Her pursuit of the concept of a ”heart” was heresy to a civilization that interpreted all existence through logic, numbers, and code.

”A heart, huh…”

Ikaros’ eyes shifted to crimson, as though lost in thought.

”Hey, hey, didn’t Master already remove your emotional limiter?! Why are you resonating with her?!”

Nymph smacked the airheaded angel lightly, then cleared her throat and turned back to Schwi.

”Explaining it bit by bit would be a pain… but since we’re basically the same type of lifeform, this’ll be easier.”

”Disable your data locks—I’ll transmit something to you.”

”...”

Schwi paused for a few seconds.

”Confirmation: data locks released. External input permitted.”

Bzzt—

A holographic interface appeared before Nymph.

She transmitted Starsea Empire’s scientific archives, summaries, and foundational data.

For most people, it would take months to finish reading that entire database of introductory materials.

But for Schwi and the Angeloids, the process was far faster.

As mechanical intelligences, they possessed unmatched data processing capabilities.

Countless lines of code streamed into Schwi’s mind—text, videos, images, simulations.

”Receiving data… parsing data…”

[Core Mode: Accelerated Computation—Enabled]

She inserted the tubular conduits on her back into the ground.

Vmm—

Instantly, hundreds of holographic screens spread around her, displaying the transmitted data streams.

Schwi activated multiple processing threads simultaneously, filtering and analyzing all information at once.

Communication between artificial intelligences was incomparably efficient—no need for words or explanations.

Everything was exchanged in code.

”Parsing complete… Confirmation: the Starsea Empire is a civilization originating from another world.”

”Correction: existence of other universes beyond Disboard detected. This theory conflicts with Network data—initiating logic recalculation…”

”Inference: Starsea Empire theory confirmed. Overriding original model.”

Schwi muttered to herself as she processed the overwhelming streams of data.

Some of the Starsea Empire’s records contradicted the knowledge stored in the Ex-Machina Network, yet she quickly identified that the Empire’s theories were far more advanced.

”Confirmation: Starsea Empire technological level exceeds Network capacity…”

”Parsing conceptual framework of the ’heart’…”

Then, within the Empire’s historical archives, she found something that shook her logic systems—the Empire was ruled by a human, and populated by humans.

This completely contradicted the Ex-Machina’s understanding of the species.

——That weak race surviving in Disboard was already improbable, let alone building a powerful civilization.

Driven by curiosity, Schwi began parsing the Starsea Empire’s history.

Beep—

A flood of incomprehensible data surged through her mind.

From the Azure World onward, there were countless concepts she could not quantify.

New species, new worlds, each with its own rules and systems…

To ordinary people, these were merely fascinating discoveries.

But for the Ex-Machina, who analyzed through absolute logic, the data was full of impossible contradictions.

”Parsing: Shipgirl biological model… failed.”

”Parsing: Synapse civilization… failed.”

”Parsing: Starsea Empire’s highest entity—Nyarlathotep… failed. Error! Error! Error!…”

A cascade of error codes flooded Schwi’s vision.

”...”

”Hey, stop it already! Don’t try to compute everything—Outer Gods can’t be logically modeled!”

Nymph tried to intervene—

Pfft—

A puff of white steam rose from Schwi’s head, like an overheating circuit.

”Computation logic critical failure. Energy overload.”

Pop—

Schwi crashed.

...

An hour later.

”Master, that’s what happened.”

”We found Schwi. Nymph uploaded the Starsea Empire’s data to her, and it seems her system encountered… a bug.”

On the bridge of the Eternal Snowfall, Ikaros gently placed Schwi on a sofa.

”Ooh—”

A group of shipgirls immediately surrounded her.

”She’s adorable!”

Victorious’ eyes sparkled.

Even in standby mode, Schwi’s delicate face and petite form radiated a quiet beauty that drew everyone’s attention.

”How did you manage to crash her?”

Belfast peeked over curiously.

”Report, Master: it was initiated by Nymph. She claimed it would improve communication efficiency.”

Ikaros answered matter-of-factly.

”Hey!!! You and Astraea didn’t stop me either!”

The blue twin-tailed loli yelled in protest, clearly dissatisfied with being blamed.

”...”

Grey crouched beside Schwi, scanning the small mechanical girl.

”Hmm… Ex-Machina. Interesting.”

”Their design’s similar to the Angeloids—a gestalt-based collective intelligence, yet each individual retains an independent mind… quite the fascinating species.”

”Her computational logic’s a bit outdated though… judging by her attempt to quantify the concept of ’heart,’ I’d say the Ex-Machina haven’t developed true sentient AI yet.”

Even among mechanical lifeforms, there were degrees of sophistication.

Low-grade industrial robots could only obey basic commands without advanced reasoning.

The Angeloids were more intelligent—capable of emotion, intuition, and self-awareness.

Grey, on the other hand—a nanomachine-based superintelligence—was already beyond human.

”So what do we do with her? Send her to Bulin for repairs?”

Yukikaze poked her head in.

”No need. She overloaded due to recursive computation—an infinite stack of logic errors caused system failure. I’ll fix the bug.”

Grey easily hacked into Schwi’s core processor and tapped a few commands on the holographic console.

Beep—

With a soft chime, Schwi’s eyes flickered open.

”Rebooting…”

”Confirmation: selecting personality module…”

Data streams flashed across her eyes as she sat up—and suddenly, her expression shifted into one of sultry charm as she gazed at Setsuna.

”Commander-sama, are you pleased with Schwi’s body?”

”Would you like to have dinner first, bathe together with Schwi, or do something naughty right away?”

”?”

Setsuna and the shipgirls froze.

Taihou: ”WTF???”

—

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