Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Whoa—”

Before long, the bridge of the Eternal Snowfall was bustling.

Dozens of shipgirls, Spirits, and ordinary girls had gathered together.

Even some goddesses recruited from the Konosuba world were present—alongside the long-time library shut-in, the dragon girl Lucoa.

”Is there any chance we can go to one of the new worlds?”

Kanae and the others were itching for action.

Previously, during the Re:Zero world expedition, each squad had performed admirably—accomplishing their assigned objectives to the best of their abilities.

Those expeditions, where they could demonstrate their power before the Commander and use their skills in real combat, had been wildly popular among the teams.

Now everyone was eager for another chance.

”Hmm... things are a bit different this time.”

Setsuna projected the star map before them.

At the same time, Yat Sen distributed simplified dossiers for the five newly discovered worlds.

Each file included basic information—worldviews, power systems, and general background.

”These five worlds—whether on the technological or magical side—are far stronger than any of the civilizations we’ve encountered before.”

”In fact, some of them contain true deities... and beings comparable to gods.”

”Eh?!”

Yukikaze scratched her head.

”Gods? Like Aqua?!”

”...Aqua is technically a goddess, yes—but do any of you honestly think she acts like one?!”

Setsuna’s expression went dark.

”...Probably not.”

Yat Sen sighed, massaging her temples.

Aqua was, by definition, a celestial goddess—one of the highest-ranking elemental deities of her realm, a senior figure in Heaven.

But within the Starsea Empire, aside from lazing around, eating, drinking, and letting the lunar research lolis bribe her into experiments, she didn’t exactly accomplish much.

In contrast, Eris was far more like a legitimate guardian goddess.

—Those who prayed to Eris often found themselves blessed: three gold ships in a ten-roll gacha, or miraculously guessing every answer on an exam.

”Uhh...”

There was far too much data this time. Worlds like A Certain Magical Index and Little Garden alone had mountains of setting lore.

Everyone only had time for a quick glance over their world structures and power hierarchies.

”Tsk, espers I can deal with—but actual gods?!”

Tohru frowned as she studied the Index dossier.

In most of the previous worlds, she’d never taken their enemies seriously.

But this time, these beings—those who could twist reality and reshape existence with a thought—these Magic Gods were on a completely different level.

”They’re even more ridiculous than the gods from my own world... Commander, you’d better be careful.”

”Umm... I’m not really good at fighting... sorry, Hero...”

Eris fidgeted with her hair apologetically.

Even though she was a goddess herself, she always felt she was on the weaker end compared to other divine beings.

”It’s fine. You can stay in the capital.”

Setsuna smiled reassuringly.

”Hmm... I find the Index world’s research into psychic abilities fascinating. It’s not purely magic—it’s more like a hybrid of science and sorcery, isn’t it?”

”And they even have a formal division between the science and magic sides? How interesting...”

Daedalus was particularly intrigued by the Index world dossier.

She read through it carefully, page by page.

There were plenty of elements that caught her attention—artificial heavens, white dwarf bombs, and research into AIM fields, for example.

The Index world’s magical and scientific systems were both complete and well-developed—essentially two fully-fledged tech trees.

”I think the magic side there is obviously stronger.”

Tohru rested her chin on her palm.

”I mean, come on—Magic Gods! When you’ve got people who can casually crush and reshape an entire world, what’s the point of science anymore?!”

”Commander, maybe if I studied for a few hundred thousand more years, I could fight them one day...”

The dragon girl pondered seriously.

Unfortunately, she was only a demi-god for now—her power wasn’t enough.

In the Index world, a Magic God was essentially a human mage who had fully transcended mortality and elevated themselves to true divinity.

She figured, given enough intelligence, she might be able to recreate the process of becoming one herself.

Tohru folded her arms, looking thoughtful.

”No... as powerful as the Magic Gods are, that doesn’t necessarily mean the magic side completely overwhelms the science side.”

Daedalus sighed lightly.

”Commander, do you remember? Back when we returned from Synapse, we discussed the relationship between magic and science.”

”No matter whether it’s science or magic, once either reaches its absolute peak, the end result is the same—they both rely on one’s will to alter the universe and bend its laws.”

”And now, we’re getting very close to that peak.”

”...”

The achievements of Synapse in technological advancement were beyond question.

They could use the Wishing Stone Tablet to create or destroy worlds—causing all things in existence to move according to their will.

Had they not decayed into a Fallen Empire over endless ages, Synapse might have become one of the most terrifying technological civilizations in the multiverse.

Now, the Starsea Empire was treading a similar path.

The Aetherophasic Engine and the Horizon Needle.

The former could elevate an entire civilization into higher-dimensional existence—turning them into literal gods of creation. The latter allowed for free manipulation of universal laws.

”So I believe that if we can achieve sufficient mastery in this area, we too could do the same as the Magic Gods.”

”If we could just reach the full power of ancient Synapse, that would be enough.”

”Moreover, we have an informational advantage—we can prepare countermeasures in advance. It’s not impossible for us to fight them.”

Daedalus spoke at length—likely the first time since leaving Synapse that she’d encountered such a worthy subject of study, such a meaningful opponent.

”Tsk, so you’re saying we should focus on completing both Ascension Wonders first, huh?”

Setsuna rubbed his chin, considering it.

”Yes. They’ll be invaluable for our continued research into law-based weaponry—tools capable of countering divine authority.”

Daedalus nodded firmly.

”When a civilization reaches a certain level, mastering the laws themselves becomes inevitable.”

”...”

”Understood.”

Setsuna drew a circle over a section of the star map.

”Once the first batch of Wonders is complete, immediately begin research and construction of the Aether Engine and Horizon Needle.”

”Daedalus—you’re in charge.”

Sharpening the blade before cutting the wood—having the Wonders’ massive resource reserves would make later development far easier.

”Understood~!”

Daedalus, Grey, and the research lolis—all those on the technological front—were brimming with confidence.

To challenge godhood through the power of science—it was the ultimate test.

”Please wait a moment, Little Setsuna.”

”Besides technological means, there’s something else that caught my attention...”

Lucoa, who had been listening quietly, suddenly opened her half-lidded eyes.

”In that world, there’s a belief that mastering all 103,000 grimoires correctly allows one to ascend and become a Magic God, isn’t there?”

”Uh... not just that. There’s a lot more preparation involved.”

Setsuna thought for a moment.

To master 103,000 ’little yellow books’—no, grimoires—meant reaching an almost incomprehensible level of magical understanding.

As for ascending to Magic Godhood, there were undoubtedly countless additional rituals and arcane steps involved.

”No matter how difficult the conditions, a method of evolving into a Magic God clearly exists.”

Lucoa’s expression turned serious.

”I agree with Tohru. Through the Index world’s system, we could take our magical side to an entirely new level.”

”Whether it’s you, me, Elma, Mio, or the Spirits—it applies to us all.”

”Oh...”

Mio blinked, then gently poked Setsuna’s arm.

”Husband, I was thinking the same thing. I’m really interested in the Magic God phase...”

”If I could expand the Ain Soph to a universal scale, wouldn’t that make me ridiculously strong too?”

Among the top-tier magic users of the Starsea Empire, few had seen major growth since arriving in the capital.

As a Feathered Serpent God, Spirit of Origin, or demi-god dragon girl, their current ranks were already extremely high.

But in the Index world, they now saw the possibility of breaking through even further.

”Hooh—”

”A Mio whose authority spans the entire universe? You’d practically be a full-fledged God.”

Setsuna tilted his head, amused—and admittedly, excited to see his wives grow stronger.

”By the way, aren’t there some female Magic Gods too...?”

One of the less serious nanobot girls suddenly raised an eyebrow.

”Othinus, Nephthys, Niang Niang... who else was there again...?”

”I remember they’re basically mummies and immortal daoists or something? Since you already went after a Cthulhu, Commander, I doubt you’ll stop there, right?”

”Tsk, Commander—your XP system evolves faster than your power level.”

”???”

Amidst the lively brainstorming session, Setsuna finalized the plan: the A Certain Magical Index world would be conquered simultaneously through both technological and magical approaches.

Harnessing the power of both sides to master the Magic God’s authority would undoubtedly propel the Starsea Empire’s strength to an entirely new level.

Of course, such a high-tier world would require time to prepare for properly.

Afterward, they briefly discussed the remaining worlds.

”What? Outer Gods?! Nyarlathotep?! Oh—she’s a cute girl version? Never mind, then.”

”Drills that pierce the heavens? A fifteen-billion-light-year-tall Gundam?! Huh?! Commander, you’re kidding me, right?!”

”Another Cosmology? Solar Sovereignty War?! Last Embryos? What even is all this?! It all sounds so ridiculously epic...”

Some of the worlds’ settings were so over-the-top they left everyone stunned.

Grey even started pondering a few useless questions.

”Uh... the Little Garden power ranking system is actually pretty interesting, huh?”

”If native small-scale hydrogen bombs are about 7-Digit, and 4-Digit beings can shatter planets—then by that standard... aren’t we casually tossing Photoids and blowing up stars every day?”

”So, what digit are you guys at?!”

”...”

Comparing power levels was always an entertaining pastime—especially when there was a formal classification system involved.

Shipgirls, Spirits, and Heroic Spirits all started chattering noisily, each estimating their own combat ranking.

”Do external artifacts count? With spell scrolls I could probably wipe the surface clean... without them, maybe around nation-level?”

Antilene matched herself against the scale and realized she was kind of weak.

Most of the ordinary human squads felt the same. Their personal strength usually hovered around nation-level or continental-level combat capacity.

With Starsea Empire equipment factored in, that number rose somewhat—but not enough to matter.

Erina Nakiri and Ryuu Dragonbane, who were serving dishes to Setsuna, froze for a moment before deciding not to join in.

”We’re just cooks. Blowing up cities, countries, or stars is way out of our pay grade.”

”At most, we blow up kitchens. If we can make the Commander’s clothes explode, that’s accomplishment enough.”

The shipgirls, meanwhile, cheered gleefully.

”Yay!”

”If a 4-Digit can blow up a star at full power, then I can fire multiple Photoids at once and smash a bunch of stars—so that makes me peak 4-Digit, right?!”

Chang Chun hugged her tiger hat proudly.

”Where the heck did you even get that logic from?”

An Shan frowned.

”By your reasoning, since Yat Sen and Harbin carry even more Photoid cannons and lances, doesn’t that make them half-step 3-Digit?!”

”?”

”...What weird webnovel nonsense have you girls been reading lately?”

Hai Tien couldn’t help but sigh at the younger shipgirls’ antics.

”...Interesting metric system, though.”

Lucoa, Tohru, and Mio glanced over the classification chart, silently estimating where they stood—then smiled knowingly without comment.

After a few minutes of chatter, Setsuna gestured for everyone to quiet down.

”In any case, that’s the situation with the new worlds. Their overall power levels are far higher than anything we’ve encountered before.”

”Conquering these worlds will grant us greater rewards as well. From now on, this will be a long-term campaign of the Starsea Empire.”

”For the foreseeable future, aside from internal development, our primary focus will be world conquest operations.”

”Eh...”

Kanae and Akame both looked disappointed, puffing their cheeks as they glanced up at Setsuna with pleading eyes.

”Commander... does this mean you won’t be needing us anymore...?”

The new worlds were on such a high tier that only Setsuna himself and the Empire’s strongest elites could participate.

The Great Tomb Unit, the Demon Slayer Squad, the Night Raid Team, the Konosuba group—most of the ordinary human and hybrid squads, as well as many Spirits and Heroic Spirits, realized their power was now inadequate.

If they went, they’d just end up as cannon fodder.

It felt like they’d returned to the early days of the Starsea Empire—when they could only cheer from the sidelines.

”As if I’d ever abandon you all.”

Setsuna pulled the two girls closer with a reassuring smile.

”Counting Madoka Magica, these world conquests are basically the main storyline missions.”

”When my mind’s had a bit of rest, I’ll open some side missions for you all.”

”In this vast multiverse, locating a few simpler worlds shouldn’t be hard, right? The ones we’ve found this round are already tough enough.”

If he wanted to, Setsuna could spend all day sitting before the Superdimensional Star Map, unlocking new worlds endlessly.

But typically, he preferred to explore a few at a time—then conquer them before expanding further.

This latest batch was full of high-tier worlds. Dealing with them constantly was exhausting. Every once in a while, it helped to bully some low-level natives for fun.

”Commander, you’re the best!”

Kanae hugged Setsuna’s neck and planted a kiss on his cheek.

Main quests or side quests—it didn’t matter. As long as she could contribute, she was happy.

And who knew? If they completed enough side missions and gathered enough experience, maybe someday their power would qualify them for the main storyline.

Each of the girls held onto that small, daring hope—that one day, they’d stand on the same stage as those transcendent beings.

...

Later that evening, most of the girls who had come to see the new world data returned to their posts, carrying piles of documents.

They buried themselves in study.

The worlds’ settings and plots were too complicated. Even if they couldn’t personally join the expeditions, they still wanted to understand what kind of realms they were dealing with.

Setsuna, meanwhile, was already plotting his next move.

”Hmm... shame Gudako wasn’t here just now.”

”If she’d seen the Tengen Toppa Gurren Lagann world, she’d have exploded from excitement. Tch...”

He chuckled to himself.

He could already imagine it—Gurren Lagann’s outrageous mecha designs wouldn’t faze Gudako one bit. She’d 100% beg him to build one for her.

Even if it meant offering herself up in return... who knew what kind of form she’d take by the time she faced Goetia again?

”Fine, the Evangelion world can stay hers. Since Ritsuka’s so eager to pilot Strelizia against the Angels, I’ll let her go. A single Singularity run won’t take long anyway...”

”The META division’s still conducting research—it’ll probably take half a month. In the meantime... let’s find an easier world to warm up with.”

He swept his gaze across the star map.

His eyes landed on the Haiyore! Nyaruko-san universe.

Officially categorized as a Tier-IV magic world—technically higher than No Game No Life.

But in a way, Setsuna found it the easiest target.

All he had to do was recruit Nyaruko and her fellow Cthulhu girls.

Sure, that world had its share of Eldritch abominations and ”Old Ones,” but it was far from the grim horror of Lovecraftian myth.

In that setting, the so-called Outer Gods were actually part of a galactic organization called the Space Union, strictly abiding by cosmic law.

They handled things like protecting undeveloped planets, cracking down on illegal pet trade, and preventing interstellar trafficking.

As long as he didn’t plan to conquer the entire universe, dealing with those Outer Gods shouldn’t be hard—in fact, they might even be comedic.

—And Setsuna had no interest in fighting gods or horrors for no reason. Too much work, not enough gain.

It would be just like the Dragon Maid world again—with a bit of effort, he could easily charm a few top-tier powerhouses onto his side.

”Alright, let’s go pick up some Cthulhu girls.”

He snapped his fingers and stood up.

”I’ve heard there’s a cosmic proverb over there: ’The happiest life is to marry Shub-Niggurath, live in a non-Euclidean house, hire a Shoggoth as your maid, and keep Lilith as your mistress.’”

”Time to see for myself...”

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