Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Who’s next? Are there any other Witches nearby?”

After taking care of the troublesome Witch of Vanity, along with Echidna and the other small Witches, Tohru turned toward Mio, the one leading the group.

”Hmm...”

The Spirit of Origin tapped a few times on the holographic interface, releasing a faint spiritual pulse as she sensed the surroundings.

”The Witch of Envy.”

”Oh, her?”

Tohru and Elma glanced over the data.

At this point in time, it was still early before the spiritron transfer alignment—the Witches had only just begun awakening their powers, or hadn’t even awakened yet.

The girl who would one day devour half the world and be sealed by the Three Heroes was, for now, merely a young girl who had just obtained her power.

To abduct her would be the easiest thing in the world.

”In that case, perhaps we can try a different approach? Technically, this should still be the Satella personality...”

Mio thought for a moment.

Half an hour later—

Vmmm—

Another portal opened within a hidden refuge.

A silver-haired, violet-eyed girl in a long dress—identical in appearance to Emilia—stared blankly at the women before her.

Among them was even her colleague, and the Witch of Greed whom she could hardly stand.

”Who are you?...”

Whoosh—

Mio opened her Territory, and the world shifted into a still black-and-white.

”Satella, would you like to visit another world with the other Witches?”

”The Starsea Empire will grant every Witch of Sin the respect and treatment you deserve. You no longer need to live in misunderstanding and hostility.”

”Of course, we’ll also help you manage the Witch Factor within you—and the other personality—so there won’t be any future trouble.”

”???”

”Eh?! What—what are you talking about?!...”

...

One day later.

Lugnica Kingdom Administrative Center — Spiritron Transfer Site.

[Reverse Summoning System: Ready]

[Recall Targets: Eleven confirmed]

[Spacetime structure stable. No worldline distortion detected. Initiating recall sequence—]

Whoosh—

The massive spherical spirit-energy device roared to life, causing minor spatial distortions around it.

Blinding blue light converged and reassembled atop the platform before the device—gradually taking the shape of eleven figures.

They were none other than Mio, Tohru, and Elma’s trio—and the eight Witches of Sin.

The newcomers looked around with curiosity and astonishment at their new surroundings.

”Welcome to the world four hundred years in the future. You now stand within the borders of the Starsea Empire.”

The Observer operating the device waved a few tendrils in greeting.

”Hmm, the spacetime seems perfectly stable this time? Aside from a few minor bugs, extracting the Witches didn’t cause any significant disruption to the current timeline?”

”Excellent, excellent. Is that because the Commander’s presence stabilizes the worldline?...”

The small loli carefully read the data logs. Having partially mastered the laws of mathematical weaponry, the R&D Department now possessed limited capabilities to correct temporal distortions.

Thus, even recruiting from the past no longer produced severe butterfly effects.

Minor fluctuations—they could handle themselves.

”Starsea... Empire...”

The Re:Zero world four centuries later was vastly different from what the Witches had known.

Especially the newly built administrative complex, and the sight of Angeloids and shuttles soaring through the skies—it all left them utterly dumbfounded.

The Witches of Lust and Pride trembled in awe and fear.

Only Echidna, however, was entirely consumed by exhilaration—like a scholar who had just discovered a new continent.

Knowledge.

From the unfamiliar ships, buildings, angels, and even the people themselves, she saw an infinite expanse of knowledge waiting to be explored.

The Witch of Greed’s thirst for understanding urged her forward, compelling her to learn everything about the Starsea Empire—this interstellar superpower that spanned the cosmos.

”Ah... truly... magnificent...”

She crossed her arms, twisting slightly with a strange, satisfied smile—one that Tohru had only ever seen in certain... unspeakable situations.

Indeed, people’s tastes were different—Tohru sighed inwardly.

Clank—

A small spacecraft landed before them.

”Everyone, I’ll be taking you to meet the Commander.”

”Please follow instructions and maintain proper decorum.”

Mio led the group aboard the starship.

Though their time together had been short, the Witches already held immense respect—and fear—for the Spirit of Origin and the two dragon girls beside her.

Even the Witch of Vanity, who was usually the most eager to stir trouble, didn’t dare speak a word and obediently followed behind.

Vmmm—

After the ship broke through the atmosphere, the Witches saw the starry expanse of space through the windows for the very first time.

And above the planet—an enormous fleet of starships, stretching beyond sight.

For a moment, they were completely dazed.

For those who had lived their entire lives in a feudal world for decades—or centuries—the sudden leap into the cosmos was overwhelming. Even powerful Witches couldn’t help but huddle together nervously inside the shuttle, afraid something might go wrong.

Clank—

Before long, the shuttle docked with the battleship carrying Setsuna, sliding smoothly into its hangar bay.

The Witches of Sin followed cautiously behind Mio, walking down a long corridor.

After passing through inspection and identification by Angeloids, they entered the starship’s command center.

”My dear husband~”

”I’ve brought back the people you wanted~”

The moment she saw Setsuna, Mio transformed completely—leaping straight into his arms.

”See? I was fast, wasn’t I? Faster than anyone else, right?”

”Mmm, husband, honestly... making me go fetch other girls for you. Next time, you’re not allowed to do that~”

Mio pouted, snuggling close. The soft pressure against Setsuna’s chest was warm and intoxicating.

”You’ll have to make it up to me tonight~”

The Witch of Vanity nearly went blind from the scene.

What’s with this woman?!

A moment ago, she had been terrifyingly ruthless—Pandora had no doubt the Spirit of Origin could crush her into paste with a single thought.

And now, she was acting like a harmless, lovestruck girlfriend?

”Alright, alright—” Setsuna soothed Mio gently.

”Commander, we’ve successfully recruited eight Witches of Sin—or rather, seven, to be precise.”

Elma, watching Mio and Tohru getting all affectionate, felt entirely out of place.

Deciding to change the topic, she began making introductions seriously.

”This is the Witch of Envy, Satella. This is the Witch of Greed, Echidna. This is the Witch of Pride, Typhon...”

”...”

The Witches didn’t respond immediately—they were studying Setsuna instead.

The aura he exuded was unlike anyone they had ever met. Even the great heroes of the world paled in comparison.

He carried himself with the confidence and majesty of a true ruler.

The kings of the surface world meant nothing to them—but this man clearly stood on a different plane from those pampered monarchs trapped in their gilded palaces.

He possessed a pride that looked down upon all creation.

Even just seeing how the Spirit of Origin adored him made it clear—this was no ordinary man.

”Oh...”

The Witches’ attire and appearance were somewhat eccentric by the standards of the Re:Zero world, but in the Starsea Empire, no one batted an eye.

After all, shipgirls, Spirits, and Heroic Spirits all had their own distinct fashion.

The only one who stood out was the Witch of Gluttony, Daphne.

The gray-haired girl, appearing even younger than Emilia, confined herself within a black coffin.

Her body was bound by restraints, her eyes covered by a blindfold.

The coffin itself floated, supported by magical appendages that allowed her to move freely.

”Direct eye contact with her Mystic Eyes induces uncontrollable hunger. To prevent accidents, the Witch of Gluttony normally appears in this form,” Tohru explained.

”But once we study and decode her Authority, we might be able to make it manageable.”

”So... a different version of Medusa, huh...” Gudako commented with curiosity.

Beside the gathered Witches stood a young girl with long purple hair, looking slightly younger than the rest.

There was no trace of any Witch’s aura coming from her.

”And who might this be?...”

Everyone stared at the unfamiliar yet strangely familiar girl, unable to match her with any Witch they knew.

”I... I’m Sekhmet...”

The girl’s voice trembled slightly, breaking in fear as she spoke.

”The Witch of Sloth?!”

”No, Commander—she hasn’t awakened her Witch powers yet,” Elma clarified, shaking her head.

”When we found her, Sekhmet had been exiled to the wastelands by her tribe and family. They used forbidden rituals, attempting to summon their so-called progenitor, and Sekhmet was the result of that experiment. But it seems her kin weren’t pleased with the outcome.”

”When we discovered her, she had just been abandoned. So, we decided to bring her back.”

Since she had not yet awakened the Authority of the Witch of Sloth, Sekhmet was, for now, just an ordinary girl.

Faced with an unfamiliar environment, she trembled with fear, hiding behind Elma’s back.

”P-please... don’t hurt me...”

The purple-haired girl lifted her head timidly, glancing up at Setsuna.

”...”

Setsuna closed his eyes and sighed softly.

”Let her live a normal life for now.”

According to the original course of events, she would awaken her Witch powers only after enduring great suffering.

Bringing her here early might actually be better.

Besides, having an unawakened ’candidate Witch’ could prove useful for researching this world’s magical systems.

As for one less of the Seven Witches of Sin? It didn’t matter.

The Witch of Vanity could fill that role perfectly.

”What about the Warlock of Melancholy? I remember he was one of the masterminds behind some incidents, wasn’t he?” Albedo asked casually.

”We took care of him along the way. Nothing impressive at all,” Tohru shrugged.

”...Fair enough.”

Setsuna decided that as long as the result was correct, the process didn’t matter.

With Mio and the two dragon girls involved, clearing this world single-handedly was never an issue anyway.

Whoosh—

He brought up the holographic interface, reviewing the mission objectives.

”World conquest—complete. Witches of Sin—recruited. Emilia, Ram, Rem—secured. Relevant data—acquired...”

”All objectives achieved. Major victory. Triumphant return!!”

...

Passing through the teleportation anchor, amid the cheers of lolis, shipgirls, and other companions, Setsuna returned, bringing with him the native girls from the Re:Zero world. Their ship descended onto the starship landing base near the capital.

”Come on, take a look at your new home.”

When the hatch opened and everyone set foot for the first time on the territory of the Starsea Empire—time seemed to stop once more.

Whether it was Ram and Rem, chattering excitedly beside the Royal Maids, or the Witches of Sin led by Mio—they all stood frozen, eyes wide, mouths slightly open, unable to respond for a long while.

”Ah...”

The colossal city stretched for kilometers, beyond the horizon.

Starships and Angeloids flew gracefully among futuristic anti-gravity structures, while countless Bulins worked tirelessly with incomprehensible technology to expand the outer sectors of the city.

The Empire’s administrative complex alone dwarfed the capitals of any kingdom or empire they had ever known.

A capital of the interstellar age—where ultimate prosperity met science fiction.

Countless forms of magic and technology intertwined here, forming systems so advanced that even a lifetime of study would not suffice to comprehend their intricacies.

Only now did Pandora, Echidna, Crusch, Anastasia, and the others truly understand what Albedo had told them earlier:

”We are but a tiny, insignificant fragment of the Starsea Empire.”

Compared to the interstellar empire before them, even the undead legions that once swept across their world seemed trivial.

The dark-glimmering starships cruising through the skies alone exuded enough pressure to make them tremble.

The entire Re:Zero world was but one of dozens of vassal worlds under the Empire’s dominion—an unremarkable one at that.

A world conquered, assigned to the Sophons, and long since beneath Setsuna’s personal concern.

”So they really did hold back—”

Echidna, the most intelligent among the Witches, was the first to react.

Through the Book of Wisdom, she had already learned roughly how the undead legions had conquered the Re:Zero world.

Now, she had no doubt that if the Starsea Empire truly unleashed its war machines, they could crush an entire planet in moments.

—Far more terrifying and efficient than Satella devouring half the world, as foretold in prophecy.

”...”

Pandora, who normally wore a serene smile, had lost it completely.

Her blue eyes swept across the ships, the angels, and the naval base in the distance.

Her expression remained composed, but within, her heart surged with chaos.

Beyond comprehension.

Spaceships, anti-gravity, beings transforming between starships and human forms...

This was something even greater than the Spirit of Origin’s power—it was beyond the Witches’ understanding.

The last flicker of ambition she’d had—to manipulate reality or meddle with fate—was gone.

She loved control, yes—but she didn’t have a death wish.

Best to behave for now.

”Scared again?”

Only when the welcoming shipgirls and lolis surrounded them did the Re:Zero girls finally snap out of their daze, quickly following behind Setsuna and the Royal Maid Corps.

”Don’t mind them. Every newcomer acts like that their first time in the capital.”

Leading the group, Formidable glanced back at the giggling Butterfly sisters.

”What are you two laughing at? You were just as bad when you arrived.”

”!”

”The city wasn’t even this big back then! And there weren’t any starships, okay?! Just farmland and tractor-chickens—wait, no, Manjuus!”

Shinobu protested indignantly.

They suddenly realized how much they had changed—how their sense of belonging had shifted completely.

Demon Slayer, Akamae, or any other worlds they once called home? Unfamiliar now—so unfamiliar.

...

Later that evening, inside the grand banquet hall of the administrative center—

After a grand victory celebration, Setsuna began the routine debriefing for the recent conquest.

All team members sat upright, both nervous and eager for their Commander’s assessment.

”Hmm...”

”This world conquest operation was carried out independently by each squad. Overall, the campaign went smoothly.”

”All squads have completed their assigned objectives.”

Setsuna opened the holographic interface, which clearly displayed every squad’s mission data.

Each small objective, when combined, formed the grand strategy for world conquest.

”Casualties this time were far lower than expected. Aside from Shalltear, no other squad required resurrection scrolls or revival spells.”

”Losses among the ordinary undead troops are considered renewable resources—so that’s of no concern.”

”By leveraging information superiority, anticipating the enemy, and preemptively developing countermeasures against powerful foes—you all performed admirably.”

He didn’t hold back on his praise.

Akame, Kanae, and the others tried to contain their excitement, their eyes shining with a restrained joy.

Compared to receiving equipment or gifts from their Commander, proving their worth in a world conquest and earning his personal approval was far more satisfying.

”...”

Meanwhile, Shalltear—who had self-detonated with the Sword Saint—found herself to be the only unexpected casualty. Still, upon reflection, taking down the strongest combatant in the Re:Zero world singlehandedly was a fair trade.

After all, she could always count on the Commander to bring her back.

”The Great Tomb squad conquered three nations and eliminated multiple Sin Archbishops. Their performance was the most outstanding. As promised, I’ll grant them their reward.”

”The Demon Slayer Corps, Night Raid, Chaldea... yes, all performed well too...”

Setsuna smiled as he reviewed the achievements of each squad.

Mio, Tohru, and Elma were considered exceptions and not counted in the evaluation.

The Konosuba squad, on the other hand, had nearly caused another incident—as expected of them.

”Commander, please let us handle the next world conquest too!!!” Kanae raised her hand eagerly, prompting a round of cheers from the others.

”Yeah, yeah! You just sit back and watch, Commander—we’ll take care of it~”

”Let us go play in more worlds~”

”Ahem. If I find a suitable target, perhaps.”

Setsuna thought for a moment, then nodded.

”I’ll browse the starmap later and look for other worlds.”

Watching each squad wage war across worlds from the comfort of his flagship—leisurely and entertaining. Perfect for lower-tier worlds.

After analyzing the overall operation, he reviewed their routes and tactics, noting a few minor flaws and potential improvements.

”Shalltear, remember to follow Albedo’s commands next time—don’t act on your own.”

”Iris, think twice before charging the background bosses with the Crimson Demons—recklessness won’t help.”

Since the operation had gone smoothly overall, there were few mistakes to address.

Each of the named individuals nodded in acknowledgment.

The Crimson Demon lolis, however, looked rather disappointed—they hadn’t even gotten to finish their god-slaying project before being called back mid-way.

”Hmm...”

After the debriefing concluded, it was time to tally the spoils of war from the Re:Zero world and arrange housing for the new arrivals.

”All the books from the Sage’s Tower have been safely transported, including the Book of the Dead and several Re:Zero grimoires.”

”Everything has been stored in the Imperial Grand Library for Rukoa to catalog.”

Most of the loot, of course, came courtesy of the Konosuba team, so Setsuna unhesitatingly dumped the sorting work on the librarian.

”As for everyone else...”

”As usual, the younger ones will attend school first to learn about the Starsea Empire’s fundamentals. Ram and Rem—join the Royal Maid Corps under Belfast’s command.”

”The rest can form a new operations squad, led by Emilia.”

”Eh? Me?!” The silver-haired girl blinked in surprise.

She had barely thawed out from her ordeal, and already she was being appointed squad leader—completely caught off guard.

”As for the Witches of Sin...”

Setsuna thought for a moment.

”Mio, they’re under your care for now. Make sure the younger ones receive proper education, and have the Magic Academy study the Witch Factors and Authorities.”

”In addition to our shipgirls, Spirits, and Heroic Spirits, we’ll establish a new Witch Corps in the future.”

”Witches, and someday... magical girls. They’ll have to get along peacefully.”

—

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