Crossover Shipgirls: Building a Dimensional Empire from Scratch

Clap—

With a snap of Setsuna’s fingers, time and space within and around the Eternal Snowfall distorted, plunging the outside world into a state of near-complete stasis.

He leaned back on the sofa as a maid approached, serving him drinks and snacks at just the right time.

”Snacks prepared by Erina, please enjoy~.”

Shoulder massage, tea pouring—the whole sequence flowed like water, clearly practiced to perfection.

Some of the maids were ones even Observer had rarely seen.

Aside from the original Royal Maids, there were now members from the Pleiades, the Dragon Maids, and even a few catgirls.

”...”

Observer blinked, a little dazed.

She had no idea why Setsuna had brought her aboard.

Was someone really interested in Siren girls? For real?

”Come here.”

Setsuna crooked his finger at the small loli.

”W-what… what do you want?”

For once, Observer showed a trace of fear. She had the distinct feeling she was about to be completely devoured.

—Talking big was one thing; actually doing it was another.

The strongest king of Chaldea had already proven that much.

”Didn’t you always complain that I was biased? Said I discriminate against Siren girls?”

”Well then, I’ll give you the same treatment as the others.”

Setsuna patted his leg.

”Guh…”

The Siren girl’s pale skin flushed red—a rare sight for her.

The pink on her cheeks only made her look cuter.

Step by step, she shuffled over to Setsuna, shyly sitting down beside him.

”Why so shy now? Weren’t you just acting all smug earlier?”

Setsuna pulled her into his arms.

One hand gently stroked her smooth, fair back and circled around her waist.

Her body was cold, like the sea itself, yet her skin was delicate and soft.

White hair, golden eyes, black beast-ear-like decorations on her head, and a black silk short top that barely covered her upper body.

That kind of outfit was usually what Setsuna had Kanae or the others secretly wear at night—but Observer naturally treated it as her everyday attire.

”Heh, who knew you actually had a little something going on there.”

Setsuna gently patted her head.

Though she looked like a loli, Observer’s figure was actually better than Nagato’s.

”Eh?”

After her initial shock, Observer suddenly felt something strange.

Warmth and safety.

It was odd—she had drifted across the seas for countless years, monitoring experimental zones and shipgirls, collecting data…

Yet no one had ever hugged her before.

The Arbiters were superiors, the Experimentals were colleagues, and shipgirls were enemies—they were always fighting.

The sea was cold, and so was space. But Setsuna’s embrace was warm.

That rare warmth calmed her anxious heart. She closed her eyes, curling up in his arms, wearing a blissful expression.

”You’re actually kind of cute when you’re quiet.”

Setsuna pinched her cheek.

”I’m always cute! I’m the cutest in the entire port area!”

The little loli puffed up her cheeks.

From behind her, several mechanical tentacles emerged from her floating rigging, waving threateningly at Setsuna in protest.

”Commander! You pervert!! Even Sirens aren’t safe from you, hentai!!!”

”Put those things away.”

Setsuna chuckled, tapping her lightly on the head.

”O-okay.”

Observer obediently retracted her rigging, her head rubbing against his chest like a cat.

”Fuu—”

”Hm?”

Before long, she noticed something unusual.

Blinking, she looked up with a sly smile.

”Commander, that’s naughty~”

”Can’t hold yourself back already? How shameless, such a lewd Commander~.”

”...”

Setsuna thought it was only natural that holding a cute, restless girl in his arms might stir some reaction.

But this little gremlin had such a mischievous personality—who knew where she’d picked up all these weird phrases.

He had originally planned to chat with her a bit, build some rapport, and let things flow naturally.

But a brat like this clearly required a firm hand.

”You little imp—can’t let you keep that attitude.”

”Yah?!—”

He scooped Observer up and carried her toward the bridge.

...

”Ugh…”

When sunlight once again filtered through the porthole, Observer groggily sat up, rubbing her eyes.

Because of the time distortion effect, the Eternal Snowfall simulated day and night through its holographic dome—so the sunlight was artificial, generated by the ship itself.

Half-asleep, she reached to the side—and accidentally touched something soft.

Turning her head, she saw tousled ivory twin-tails draped over a stunning, voluptuous body.

Illustrious-class No. 3 ship—Formidable.

”Eh?”

The little loli jolted upright instantly.

She quickly grabbed a piece of clothing from her rigging and changed, her legs still trembling slightly.

Too terrifying.

The Commander and the shipgirls were both too terrifying.

They’d ganged up on her—teasing, squeezing, bullying her from every direction.

Observer suspected Formidable had been taking revenge. Years ago, during a battle with the port, she had bombed Formidable’s deck.

So yesterday, Formidable teamed up with the Commander to ”retaliate” in every possible way.

She even said that next time, she’d bring Taihou, Richelieu, and Chen Hai along too.

”Eeehh—”

The little loli paled at the thought. If all the shipgirls came to settle old scores, she’d be doomed.

Especially Taihou—if she and the Commander got involved, Observer would definitely end up dizzy and dazed, making ahegao faces with heart-shaped eyes and peace signs.

Next time, she decided, she’d rather stick with Spirits, Heroic Spirits, or normal girls at least—she didn’t have grudges with them.

”How are you feeling?”

Seeing Observer staggering out, holding onto the wall, Setsuna asked with a chuckle while having breakfast.

”Hentai Commander, is that all you’ve got? No feeling at all~ You’re just a hentai Commander~”

—That was what Observer wanted to say.

But considering that further teasing might get her ”punished” on the spot, she held her tongue.

”A little tired,” the little loli muttered, pouting.

”Then rest for a bit.”

Setsuna signaled for a maid to bring her breakfast.

”Hm?”

Observer noticed that there were a lot more little shipgirls on the bridge now.

Little Formidable, Little Enterprise, Little Belfast, little cat-eared girls—all gathered around the larger shipgirls, chattering cheerfully.

Yat Sen was handing out presents to each of them.

”Here, little Cheshire, yours.”

”Little Eugen, yours—handle it carefully.”

”Little Belfast, this is the tea set you wanted…”

Each small shipgirl received a gift box and immediately began tearing it open with excitement.

Inside were things like magical trinkets, imported snacks from other worlds, and various curiosities.

They weren’t expensive, but they were new and fun—each little shipgirl hugged her present happily and ran off to share with the others.

While handing out gifts, Chen Hai was also taking notes.

”Hmm… there are quite a few children in the capital too. We’ll need to prepare some for them as well.”

”And don’t forget the ones at the Starbase. What was it that Kayo Senju liked again?…”

”What’s going on?” Observer tilted her head curiously.

”Well,” Setsuna replied, ”according to other-world customs, today’s Children’s Day. So every child gets a present.”

Since lolis made up a considerable portion of the Starsea Empire’s population, he figured renaming it ”Loli Day” didn’t sound too strange.

Nearby, Nagato was struggling fiercely against Musashi and Illustrious, refusing their attempts to feed her.

”I am a battleship!! Not a child!! I don’t want presents!!!”

”Stop giving them to me!!!”

”Eh?!”

Observer watched in amazement.

”Every child gets a present? That’s awesome!”

”Commander, Commander! I want one too!!”

She ran up to Setsuna, eyes gleaming.

”You?”

Setsuna raised an eyebrow.

Given that Siren girls were older than most shipgirls, and she just happened to look small, she really had some nerve asking for a Children’s Day gift.

”I already gave you one, didn’t I?”

”When?!” she protested, spreading her hands.

Setsuna pointed at her stomach.

”I gave it to you yesterday. Forgot already? If it’s not enough, I can give you more.”

”???”

”Wah! Commander, you hentai!!!”

...

[All ships in position. Each unit has integrated into the Dreamweaver Network.]

[Spatial beacon locked... target universe coordinates confirmed. Departure commencing.]

[Estimated travel time: 552 hours, 15 minutes, and 6 seconds.]

[Executor vanguard forces ready. Megastructure armaments activated. Confirmed—no hostile units detected.]

With a crisp AI prompt tone, a massive fleet of black and teal ships glided steadily through the void.

At the forefront were countless strange vanguard vessels—some shaped like giant eyes burning with cyan flames, others resembling sea monsters with sleek, aggressive designs.

Inside the larger ships stood Siren Enforcers—silver-haired women in black uniforms, each exuding an aura of authority.

Just as the Experimentals had mass-produced Sirens and low-tier Executers for logistical duties, the Arbiters too had their own subordinate units: Enforcers who acted in their stead, carrying out the will of the higher Arbiters.

The number of Enforcers-class Sirens serving as vanguard commanders was small, but each commanded a detachment fleet ranging from hundreds to thousands of ships.

They led the charge for the Arbiters—clearing the path ahead.

At the center of the formation were the twelve Siren Arbiters themselves.

Each had manifested her complete flagship form, surrounded by the Siren fleets like stars orbiting their sun.

Navigating the void was notoriously difficult—one wrong step could lead them astray into another dimension entirely. Fortunately, Siren mastery over spatial technology was unparalleled. Guided by the beacon signal, they quickly located their route.

Precise calculations soon produced the optimal trajectory and projected arrival time.

”Ah~ Finally, we can leave this wretched place~”

A silver-haired, blue-eyed Arbiter in a white chiffon dress leaned lazily against her bridge console, yawning.

”I was starting to rot from boredom here. Thank goodness Purifier and Observer Alpha managed to set up that beacon.”

”...That world they’re in contains lifeforms,” said another Arbiter softly, seated atop her jellyfish-like rigging. Her tone was as emotionless as Compiler’s—flat, steady, impossible to read.

”The Experimentals call one of them ’the Commander.’ There are also several other intelligent species present.”

”Mmhm~ I know~”

Lavos adjusted the tiny ornaments on her outfit.

”Let’s just hope we don’t scare them too badly, hmm? There should be shipgirls over there too, right?”

”Hmm, maybe we should recall part of the fleet? There’s no enemy presence anyway. We don’t need that many escorts.”

”A sky-darkening fleet might terrify those oceanic children.”

Considering how rude it might seem to suddenly appear in someone else’s world with a full invasion-sized fleet, Lavos seriously pondered whether to show a more peaceful posture.

”No need,” replied Temperance without emotion. ”According to fragmented transmissions from Observer, their civilization has already reached an extremely advanced level.”

”I don’t think they’ll be easily frightened.”

”Tch, a moon-sized ship capable of interstellar jump and stellar-scale destruction? If the Experimentals weren’t exaggerating, I really want to see that myself...”

Empress clicked her tongue.

”If they can really build something like that, maybe they should just become the next Arbiters instead.”

”...I don’t recommend joking about your own position,” Lavos muttered darkly.

She had a feeling that if any Arbiter ever made such a suggestion seriously, both Observer and Purifier would overthrow the hierarchy without hesitation.

”So, what have they been doing recently? Any more updates?” Empress asked again.

”Yes.”

”As our fleet draws closer to their universe, the Experimentals’ database synchronization has improved significantly,” Temperance replied.

”Unfortunately, all data from the early disconnection period is irretrievable.”

”We still don’t know how the Experimentals reached that new world, who its leader is, or what kind of civilization it truly is...”

”We’ve only been able to receive some of their latest transmissions.”

”...”

At first, Observer had indeed been diligently recording everything she saw. But as time went on—and with no contact from the other Siren fleets for an extended period—the little loli began to loosen up… and eventually went completely off the rails.

The contents she uploaded left the Arbiters utterly speechless.

”These are the most recent records. Take a look.”

Temperance synced the database feed to the other Arbiters.

[Observer’s Log]

Day 1:

Got caught and taken aboard the Eternal Snowfall by the Commander today. That hentai Commander! Even Siren girls aren’t safe! There are so many girls on board too!! …

The Commander and Formidable teamed up to bully me! It hurt a little, ugh…

Day 2:

Good thing Siren bodies are durable—I managed to hold out. Today the Commander brought the entire Illustrious-class carriers with him. Seriously?!

Indomitable is so lazy! Not proactive at all—but I really envy her figure…

Day 3:

Ugh, this is purely for observation purposes, really. Just one more time—for the sake of data collection!!! Definitely not because I wanted to!!!

...

Observer, oh Observer… how far you’ve fallen.

As a member of the Experimentals, your duty was to closely monitor the Commander’s actions, analyze the Starsea Empire’s structure, and archive all relevant data for study…

You can’t go on like this!!

Day 4: The Commander said my body’s soft and perfect to hold. Ehehehe… so embarrassing…

Day 5: I want to give birth to a little Siren for the Commander! But he said I’m already too small… uuu…

”???”

The group of Arbiters stared in stunned silence.

In their limited exchanges with the Experimentals, the data they received had always been bizarre—but this, this was on another level entirely.

From making shipgirls to building super warships, and now… this?

What was this—Siren Girl Corruption Arc??!

What self-respecting Siren keeps a diary like this??!

Empress wanted to fly over immediately, grab Observer by the collar, and interrogate her about what in the world the Experimentals had been doing lately.

”So… we have a traitor among us?” Lavos tilted her head.

”...Or maybe it’s better to say… our traitor’s been converted?”

”...”

A few Arbiters suddenly began to worry they might one day face a… chastity crisis.

...

Elsewhere—

After thoroughly savoring the Siren girl’s charm, Setsuna gave glowing reviews and sent her back to the port before returning to work on the transdimensional starship.

Occasionally, the little loli would still sneak aboard the Eternal Snowfall, pretending to complain while secretly enjoying it.

Soft, cool… yes.

When his skill cooldowns were nearly reset, Setsuna refocused on the remaining worlds displayed before him.

Shua—

The star map projected several neighboring universes at a distance.

”The last batch of discovered worlds are mostly dealt with. Maybe it’s time to find a few new neighbors.”

Neon Genesis Evangelion, Re:Zero, Puella Magi Madoka Magica—

Counting the half-completed Honkai world waiting for the transdimensional ship’s completion, that made three and a half remaining targets.

Their world conquest speed was unmatched.

”Next up… hmm, EVA or RE:Zero?”

Setsuna pondered.

Neither world was particularly powerful—sending a fleet would crush them easily.

EVA’s Angels and Human Instrumentality Project had certain research value, and conquering it would also expand the selection of available mobile suits.

”Hmm…”

”Summon the fleet. We’ll discuss our next—”

As he spoke, Kanae tugged lightly on his sleeve.

”Commander, can we have a turn this time?”

The girl puffed her cheeks, her expression a mix of cuteness and frustration.

”Commander, look—we’ve been here so long, but we’ve barely joined any expeditions. We’ve changed gear so many times and learned all these new skills, but never get to use them!”

Her two companions, Shinobu and Kanao, nodded rapidly.

”Yeah! Every time, it’s either the shipgirls or the Angeloids who flatten everything—or Mio and Lady Tohru wiping out the opposition. We’re always just cleaning up afterward.”

”I’ve been training under Senju for ages in the Taixuan Eminence style. I think I’m pretty strong now!”

As she spoke, Shinobu demonstrated a few elegant sword moves.

”Don’t you girls often go dungeon diving in the Goblin Slayer world? Or help the goddesses fight Demon Kings?” Richelieu asked curiously.

”That’s different!” Shinobu protested earnestly.

”We’ve run the Goblin Slayer world so many times, I practically have the entire dungeon layout memorized…”

”We just want to help the Commander expand the empire’s worlds! We’ve lived in the Starsea Empire for so long, learned so much—we want to prove ourselves, you know?”

”Otherwise it feels like we’re always hiding behind the frontlines. It’s embarrassing…”

”...”

Since the shipgirls, Spirits, and dragon girls were all incredibly powerful and reliable, Setsuna usually took them on expeditions.

The starship + Angeloid combination could wipe out most native civilizations with ease.

Mio, the human cheat-code incarnate, and Tohru could also handle most magical worlds effortlessly.

The only issue was that the normal girls never got much of a chance to shine.

Most of their time was spent in the capital, waiting to see what new loot or technologies the latest expedition would bring back.

”Hmm…”

Setsuna paused to think. She had a point—it wouldn’t hurt to give them a mission of their own, a chance to prove their progress.

Wearing top-tier gear and mastering advanced skills just to run routine dungeons was indeed dull.

”Notify the other squads,” he ordered after a moment.

”This time, I’ll be assigning you your own conquest mission. Do your best.”

—

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