Crossover Shipgirls: Building a Dimensional Empire from Scratch

After entering outer space, the Eternal Snowfall’s Wisdom Cube engine operated at full power, with the spaceship cruising through the cosmos, leaving a tail flame tens of kilometers long.

Within just a few hours, the red planet Mars could be seen outside the porthole, along with Saturn in the distance, appearing as though it were wearing a straw hat.

”Our current speed is four times the third cosmic velocity! Commander, I underestimated the engine’s power at the time, meow,” Akashi said excitedly, adjusting parameters on the control panel.

”With this speed, we could land on Mars in just over 10 days!”

The ship’s performance had exceeded Akashi’s expectations significantly.

At four times the third cosmic velocity—nearly 200 times the speed of sound—the ship’s acceleration was only possible in the vacuum of space, where there were no resistance constraints.

”Uh, let’s hold off on that. Our current hulls probably aren’t suitable for operations in outer space, and we don’t have spacesuits or anything like that…” Richelieu said after some thought, sounding a little regretful.

”Can we accelerate to the speed of light?” Setsuna leaned closer, glancing at the parameters on the screen, though he didn’t understand them.

”Uh…”

”Commander, that’s still a bit out of reach,” Akashi replied, scratching her head.

”Even in the port, among the Sirens, who are more technologically advanced than us, I’ve never heard of them building a light-speed spaceship or aircraft.”

”300,000 kilometers per second! That’s not something conventional acceleration methods can achieve. Otherwise, the hull would disintegrate during the acceleration process.”

”You could try researching hyperspace travel, warp drive, or jump technology,” she added.

Setsuna patted Akashi’s head. She was indeed clever, figuring out the principle behind light-speed travel versus conventional spacecraft on her own.

”What’s that? It sounds amazing! Don’t tell me you’re going to throw another pile of technical documents at me and make me work overtime!” Akashi’s ears immediately perked up, her expression vigilant.

Every time Setsuna assigned her a task, she felt as if the Wisdom Cube inside her was crying out in pain. The constant research on otherworldly technologies often left her mentally exhausted.

”Not yet, but once I have them, I’ll definitely let you study them,” Setsuna said with a smile, giving her a gentle pat before letting her return to her seat.

”Commander, does this mean we’ve officially entered the space age?” Taihou asked.

”It seems so,” Setsuna replied, opening the statistics interface.

[Civilization Overview]

• Civilization Type: Technological Civilization

• Technological Level: Space Age (Sub-Light Speed)

• Population: 67,235

• Species: Humans, Shipgirls, Heroic Spirits

”Oh?”

Compared to the last time he checked, the population had nearly doubled.

—Specifically, the Bulin population had doubled. The naval base was still continuously undergoing Bulin fusion.

The technological level of the civilization had officially reached the Space Age.

This marked the first legitimate advancement in civilization’s technological progress.

Previously, starting from the Stone Age, Setsuna had relied on the technologies of Azur Lane to leap directly into the Pre-Space Age.

The transition from a Pre-Space Age native civilization to the Space Age was something he and all the shipgirls had worked toward step by step.

The spaceship’s resources came from this world and the Demon Slayer world, with every screw painstakingly hammered into place by the Bulins.

”Wait, so the Space Age is defined by speed?” Setsuna realized this classification standard was rather peculiar.

[The technological level of a spacefaring civilization is categorized by the maximum speed of its spacecraft,] the system explained.

[Space civilizations are classified into Sub-Light Speed Civilizations, Light-Speed Civilizations, and Faster-Than-Light Civilizations.]

[A Faster-Than-Light Civilization is the pinnacle of the Space Age. Surpassing the speed of light signifies a complete overturning and breakthrough of existing physical theories, making them akin to gods in the eyes of lower-level technological civilizations.]

”...”

”So, after reaching the stars, the next goal is to surpass the speed of light…” Setsuna mused. He felt there was still a long road ahead.

Then, suddenly, a mission notification rang out.

[Mission completed: First interstellar cruise achieved.]

Swish—

The task interface appeared before him.

[Reaching the Stars]

1. Launch an artificial Earth satellite. (Completed)

2. Build a spacecraft capable of intra-planetary system navigation. (Completed)

3. Master a power from outside this world. (Completed)

[Rewards distributed: New Authority unlocked: Interdimensional Warfare.]

[Congratulations! Your civilization has entered the Space Age.]

[You can now detect more civilizations on the Hyperdimensional Star Map.]

”...”

Boom—

A pile of blueprints fell into Setsuna’s storage space.

There were two notable items: a Dimensional Anchor, enabling free travel between two worlds, and a Wonder Building: the Sundial Array.

Setsuna didn’t bother with these for now. He planned to hand them over to Akashi once he returned.

What intrigued him more was the new authority and the ability to see more civilizations.

Swish—

Opening the Hyperdimensional Star Map, he was astonished to find a significant number of new ”neighbors” nearby.

On the star map, a few more world bubbles appeared, slightly farther from the five existing worlds he had already explored.

[Miss Kobayashi’s Dragon Maid (Pre-Space Age)]

[Overlord (Tier-II Magic Age)]

[Transformers (Space Age)]

[Goblin Slayer (Tier-III Magic Age)]

”???”

”What’s with this stuff?!”

Setsuna felt that two particularly strange worlds had somehow snuck in. One seemed like it wouldn’t pass a content review, and the other felt out of place among anime and game-related settings.

”Huh? Are we going to have shipgirls fighting Autobots now? Though… I wouldn’t mind getting my hands on the AllSpark…”

”Goblin Slayer… ugh, let’s skip that for now.”

The worldview of Goblin Slayer was disturbingly grim. While the goblins themselves weren’t much of a threat, the existence of ”gods” in that world was far more troublesome.

Besides, Setsuna wasn’t interested in meddling with secondhand issues. Once the Spiritron Calculation Engine was completed, allowing for precise control of time and space travel, it would make more sense to visit and carefully select people to recruit.

As for the other two worlds, he was familiar with Dragon Maid, having watched it before. Tohru and Kanna were cute and lovable.

But Overlord…

”Wait, is this the original world of Ainz Ooal Gown, or is it the game world?!”

Setsuna was puzzled and clicked into the diplomacy interface.

[Overlord (Tier-II Magic Age)]

A world with abundant magical and extraordinary forces. Powerful individuals possess the ability to destroy nations, though no deities with complete control over rules have appeared yet.

Comparison of Strengths:

• Technological Level: Comparable.

• Military Strength: Comparable.

• Economic Power: Like a God.

[Options:]

• Diplomacy

• Traversal

• Declare War

”...”

So it was a game world.

Setsuna was already used to seeing ”Godlike” under economic strength when comparing worlds. After all, his civilization currently had no trade activities whatsoever.

But that didn’t matter—as long as the ”gun” was strong enough, the neighbors could farm for him.

At the same time, the Declare War option had also been unlocked.

He clicked to view its details.

[Interdimensional Warfare]

Declare war on a target world to initiate a world-scale invasion and total war.

Upon declaration, a two-way portal between the worlds will be established, remaining active until one side is completely annihilated or surrenders.

The victor gains supreme administrative rights over the defeated world, as well as access to all its technologies and powers.

”Hmm…”

The ”supreme administrative rights” over a world intrigued him—especially for a game-based world, where this might function like an admin panel.

However, since their current strength levels were close, he decided to spare them for now.

With that in mind, Setsuna casually opened the diplomacy interface to see who he could contact.

Bzzt—bzzt—

The screen flickered before stabilizing.

On it appeared a skeleton clad in a black robe, holding a staff.

Ainz Ooal Gown sat on his throne, staring in astonishment at the suddenly activated interface in front of him.

This was clearly not part of the game—it was something from another world entirely.

”Uh, so I ended up contacting Nazarick after all…” Setsuna thought, unsurprised, given that Ainz was the main character of this world.

Several shipgirls peeked over at the screen.

”Whoa, what’s that?! A skeleton?!”

”So ugly!!!”

”???”

The skeleton on the other side was shocked, immediately casting dozens of defensive spells on himself. After confirming that Nazarick hadn’t been invaded, he cautiously addressed Setsuna.

”Who are you?”

”...”

Setsuna thought for a moment and decided to mess with him.

”I’m an YGGDRASIL Administrator. Let’s end this mystery game here.”

”!!!”

Ainz was utterly horrified. He leaped from his throne and began casting a barrage of bizarre spells.

”Guardians, assemble!!!”

”Activate High Alert! Nazarick is now under maximum security!!!”

”Shalltear! Albedo! Prepare for combat!! Protect me!!!”

”...”

The shipgirls watched, utterly baffled.

”What’s going on? Why is he so panicked?”

”No idea. Maybe I scared him too much. He’s probably about to fight the air now.”

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