Crossover Shipgirls: Building a Dimensional Empire from Scratch

Seasons changed, and as the distant forest's leaves began to turn yellow, the ocean breeze carried a faint chill.

The construction of the capital city had entered a new phase.

From the heights of the naval base, one could overlook Constantinople, now a bustling metropolis. At its center lay a palace-like administrative district, with residential areas, research zones, and other functional buildings sprawling out along the main thoroughfares. The streets were dotted with shipgirls and Bulins strolling about.

Many shipgirls from the port area had been drawn to this thriving city, eagerly signing up to either visit or move in. But by far, the largest population was composed of Bulins.

Thanks to the Controlled Bulin Fusion Plan, the colony's Bulin population had exploded exponentially within a short time. They were not just helpers to the shipgirls but also perfect workers.

With their growing numbers, the Bulins had been dispatched worldwide, further expanding the resource extraction efforts on Earth.

Far out in the Aegean Sea, dozens of enormous offshore drilling platforms could be seen extracting oil and natural gas from the seabed. Each platform was maintained and operated by hundreds of Bulins. Just a short while ago, building such massive structures would have been unimaginable for the settlement.

Beyond the main city lay golden waves of wheat stretching endlessly, tended to by Manjuus driving tractors.

Adhering to a philosophy of balanced agricultural, industrial, and military development, Setsuna ensured that even though shipgirls didn't need food, stockpiling ample grain was essential for unforeseen circumstances.

[Civilization Overview]

• Civilization Type: Technological Civilization

• Technological Level: Pre-Space Age

• Population: 36,271

• Species: Humans, Shipgirls

• Territory: 566,000 square kilometers

Inside the administrative building, Setsuna studied the displayed data.

In just a few months, the settlement's population had swelled to 36,000, and its territory had expanded from a humble 60-square-meter shack to 566,000 square kilometers.

Besides Constantinople and the surrounding waters, numerous simple outposts had been established across Earth.

Starting from scratch was always the hardest part. But after taking the first step and completing the initial accumulation phase, the civilization's development had accelerated exponentially.

From one person to 300, and now to over 36,000—each step marked a dramatic leap forward.

The infrastructure and productive capabilities brought by tens of thousands of Bulins were awe-inspiring. With enough resources, they could construct a medium-sized city in just a month, complete with water and electrical systems.

[Ding—]

[The system has detected that the host's civilization has reached the designated population and technological level. Initiating the next stage of tasks.]

A system notification sounded.

[Mission: Reaching for the Stars]

Mission Description:

When the first primitive human gazed at the stars for more than 30 seconds, humanity transcended being mere creatures of Earth—they became beings with the capacity to dream. For millions of years since, the purpose of civilization's advancement has been singular: to escape Earth's gravity and reach for the stars above.

Mission Objectives:

 1. Launch an artificial satellite into Earth's orbit.

 2. Build a spacecraft capable of interplanetary travel within the solar system.

 3. Master a power originating outside of this world.

Mission Rewards:

 1. Dimensional Anchor (Blueprint).

 2. Wonder Building: Sundial Array.

 3. Authority: Interdimensional Warfare.

"What...?"

Setsuna stood frozen for a moment.

It seemed that apart from world missions, the system would occasionally assign developmental tasks. Last time, it had been about establishing a civilization. This time, the directive was to head straight for the stars.

Skipping the Iron Age, Industrial Age, and even the Nuclear Age? Sure, why not.

He turned his attention to the three mission rewards:

[Dimensional Anchor]

A cross-world teleportation anchor point. Once placed in a world, it allows direct travel to that world from any other, with the owner's permission.

"This is just a teleportation anchor," Setsuna muttered, but he found it quite useful.

Previously, traveling back and forth between two worlds required him to manually open a space-time channel. Even Ning Hai and Ping Hai had to rely on him to help them collect resources from the Demon Slayer world.

Opening such a channel came with cooldown restrictions. But with the Dimensional Anchor, a single activation would allow for long-term, stable, two-way communication between worlds.

Additionally, since teleportation required the owner's consent, there was no risk of unexpected, malicious intruders.

He looked at the second reward:

[Sundial Array (Modified Version)]

A world wonder—a defensive superweapon requiring a large amount of resources to construct.

Once activated, it can deploy a "Ceasefire Field," nullifying all enemy special abilities within its range and halting all high-energy reactions and physical warheads.

The energy consumption of the Ceasefire Field scales with the strength of the enemies it affects.

"???"

Setsuna couldn't help but feel this resembled the Chronosphere superweapon from Red Alert 3, specifically from the Rising Sun faction. However, it seemed to be a heavily modified version.

Not only did it retain the original's ability to halt high-energy reactions and suppress firepower, but it also added an incredibly powerful function:

Nullifying all special abilities within its range.

Even the most overpowered gimmick-based entity would become a mere mortal within the Ceasefire Field.

It was perfect for home defense.

And it was a world wonder!

A civilization without wonders—could it even be called a civilization?

If not for resource concerns, Setsuna would've already started constructing a pyramid or the Petra Monument… After all, even a native wonder was still a wonder!

Finally, his gaze landed on the last reward:

[Authority: Interdimensional Warfare]

The ability to declare war on a target world and initiate a world-scale invasion.

Once war is declared, a two-way teleportation channel will be established between the worlds until one side is completely destroyed or surrenders.

The victor will gain supreme administrative authority over the defeated world, including all its technology and powers.

Note: Initiating interdimensional warfare will pit you against all forces within the target world, including high-dimensional entities of godlike power (if present).

"???"

Setsuna was stunned.

"This ability… isn't this a bit too thrilling?!"

Initiating warfare between worlds and completely subjugating the enemy.

Setsuna's understanding of this authority was straightforward: flip over the entire target world, crush everyone in it, and reap all their resources.

Interstate wars on Earth seemed trivial in comparison.

This would be a true "world war"—a battle where everyone, from ordinary mortals to god-like entities, would be involved.

The victor would gain ultimate administrative authority over the defeated world, along with all its technologies and powers.

The rewards sounded immensely tempting: winner takes all.

Defeat a god-like being, and you'd gain their powers.

Of course, choosing the right target for war was a skill in itself.

If the target was a weak world, there wouldn't be much to gain, and the cost of war wouldn't justify the effort.

If the target was too strong, one could easily be smacked down by some incomprehensible monstrosity.

Let's not forget—the teleportation channel worked both ways. Having one's home base invaded first would be farcical.

Setsuna glanced at the neighboring worlds.

Forget it.

The Demon Slayer world was already under his control, so there was no need to overdo it.

Azur Lane was an ally.

As for Type-Moon, Date A Live, and Honkai—those worlds were not only challenging to conquer, but each also had its share of "waifus."

Better to stick with peaceful development for now.

He could revisit the idea when a more suitable target emerged.

With that thought, he activated his communicator.

"All personnel, assemble! There's new work to be done!"

Half an Hour Later

Dozens of shipgirls gathered in the conference room.

"Commander, are we going on another adventure to another world?"

"Can I come along this time?"

Yukikaze was practically bouncing with excitement.

"Uh…"

"Well, sort of. But there are other tasks to assign first."

Setsuna laid out the three mission objectives:

"Launch a satellite, build a spaceship, and master a power from another world."

"How long will the first two take?"

The shipgirls all turned their attention to Akashi, who was in charge of research and development.

"Launching a satellite isn't hard. With the technologies from Azur Lane and Gundam, it's easy to send one into Earth's orbit, meow~."

"But building a spaceship capable of interplanetary travel… that'll take some time."

Akashi rested her head on the table, pondering.

Although the shipgirls had no prior experience with aerospace engineering, the Gundam technology tree provided by Setsuna not only included various models of mobile suits but also designs for spacefaring warships such as the Archangel, Izumo, and Minerva.

These vessels served as both carriers for Gundams and combat-ready starships capable of interstellar navigation.

Once the underlying principles were understood, replicating or reverse-engineering one was entirely feasible.

"Oh, if we can build spaceships, wouldn't that mean we could also upgrade our rigging…"

Formidable's eyes sparkled.

"That's exactly right."

Setsuna nodded.

"We could use starship construction techniques to upgrade you into space carriers, interstellar battleships, or interstellar cruisers…"

"!!!"

Several carrier and battleship shipgirls immediately became restless.

They had long envied the destroyers darting through the skies with their rocket backpacks, and now the possibility of breaking through the atmosphere and venturing into space excited them to no end.

"Akashi, my future depends on you—"

"I want to soar through the galaxy with the Commander, completing the grand harmony of love amidst the stars…"

Taihou clung to Akashi's head and ruffled her hair affectionately.

"Stop it! I can't breathe!!!"

The cat-like ears shipgirl managed to poke her head out from the suffocating embrace, gasping for air.

Setsuna, watching the scene, found his eyes glued in place.

"What about the third task?"

"To obtain a power from another world? Commander, do you have any leads?"

Richelieu shot Taihou a sidelong glance before asking.

"This one… is pretty straightforward. We have plenty of neighbors, don't we?"

Setsuna projected the multidimensional star map.

"We currently hold Azur Lane and Gundam technologies. If we can obtain another type of knowledge—be it a different branch of science or magic—it should fulfill the task."

"Looking at our neighbors, we have worlds using Honkai energy, the magecraft of the Type-Moon universe, and the spirits of the Date A Live world."

"Their systems are fully developed, so we can figure out a way to acquire something from them."

A dozen heads crowded around the star map.

"Commander, which world are you planning to visit?"

"Hmm…"

Setsuna studied the map carefully.

The Date A Live world still displayed an unresolved world mission:

[Resolve the Threat of the Original Spirit].

It didn't feel solvable yet—he had no clear approach to tackling it. Mukuro Hoshimiya was a truly daunting adversary.

"Honkai, huh… Honkai energy sounds pretty intriguing, but then we'd have to deal with Herrschers."

"The stronger the civilization, the stronger the Herrschers. What kind of nightmare Herrscher would show up here?!"

He pondered for a while, then turned his gaze toward the Type-Moon universe.

[Type-Moon/Fate/Grand Order].

This wasn't tied to a single storyline like Fate/Stay Night or Fate/Zero; the Nasuverse was home to countless Lostbelts and Singularities.

[Diplomatic Communication].

Bzzt—

The screen flickered with static.

[Connection Established: Starsea Alliance - Chaldea].

"Hello? Hello? Is Gudako there?!"

"Let's save humanity together!!!"