Crossover Shipgirls: Building a Dimensional Empire from Scratch

After getting a basic understanding of the harbor’s operations, Setsuna found himself at the seaside.

The salty breeze carried the scent of the ocean, mingling with the faint aroma of Richelieu’s elegant perfume as she stood before him. Her blonde hair swayed gently in the wind, catching the sunlight like threads of gold. Richelieu had decided to showcase the advanced technology of Azur Lane and the power of shipgirls.

”Mr. Setsuna, we are beings born from Wisdom Cubes—true machines of war.”

”Do you know what we’re capable of?”

Standing on the surface of the water, she radiated pride and confidence, a faint smile resting on her lips.

”I’m all ears.”

Setsuna gestured politely, smiling at the girl standing on the sea.

Of course, he already knew shipgirls had supernatural abilities, but in Richelieu’s eyes, he was still an unfamiliar visitor from another world. He decided to let her demonstrate her capabilities.

Click!

Richelieu raised her hand, and a projection of her battleship rigging materialized beside her.

Two quad-mounted 380mm main guns flanked her, while the bridge and command tower floated slightly behind her.

The pure white gun turrets bore the golden Lorraine cross—a symbol of Iris Libre. Intricate golden patterns adorned the base and top of the rigging, exuding the same elegance and nobility as their owner.

A long spear appeared in Richelieu’s hand, with a golden ribbon tied into a delicate fleur-de-lis at its hilt.

”How beautiful.”

Setsuna praised sincerely.

”Beauty is not a fitting term for weapons of war, but I will accept your compliment.”

Richelieu nodded.

”Can you project your true form?”

Setsuna asked curiously. He had never been aboard a shipgirl before.

Ahem, he had never been aboard a shipgirl’s actual battleship form.

”We can, but most of the time we prefer to fight in rigging form—it’s more agile. Using our full form is rare.”

Richelieu dismissed her rigging with a wave.

Flash!

On the sea near the harbor, a massive battleship, approximately 200 meters long, appeared.

At close range, the main guns on the deck were even more intimidating.

The tiered command tower rose dozens of meters high, surrounded by countless secondary guns. Setsuna had to crane his neck to take in the full majesty of the ship.

It was the Richelieu, the lead ship of the Richelieu-class battleships.

”Come aboard. You’re the first person to set foot here.”

”I rarely invite anyone to board my ship, so consider this an exception just for you.”

Richelieu extended an invitation to Setsuna, allowing him to climb onto the deck.

”I never thought I’d get to see this ship in person.”

Setsuna marveled.

If the French Army had lost face with its 39-day collapse in WWII, Richelieu was the last beacon of French pride.

She had fought across Europe, North Africa, and the Pacific, standing alongside the Iowa, North Carolina, Illustrious, and Saratoga, shelling the Japanese homeland and even participating in their surrender ceremony.

”You know quite a bit.”

Hearing Setsuna recount her history, Richelieu seemed genuinely pleased.

”Just a passing interest in history.”

”Still, you’ve made some impressive upgrades, haven’t you?”

Walking into the bridge, Setsuna noticed that the Richelieu was nothing like the outdated WWII battleship he’d envisioned.

The outer armor was not the steel-gray typical of early battleships but a sleek, silvery-white metal etched with golden patterns, giving it a luxurious and futuristic appearance.

The command room was equally extravagant.

Red carpets, gold-trimmed furniture, and an overall European aesthetic made it feel more like the Palace of Fontainebleau than a warship.

Advanced electronic devices were scattered throughout the space—technology far beyond anything from WWII.

”You’ve underestimated me, haven’t you?”

”My name comes from that battleship, yes, but thanks to Wisdom Cube technology and harbor upgrades, I’m far from an outdated relic.”

”In a pure naval battle, I could probably destroy an entire IJN or Eagle Union carrier strike group on my own.”

Richelieu raised her command baton, and her two turrets adjusted their angles, firing at the distant horizon.

Boom! Boom! Boom!

The shells caused massive waves to surge skyward.

Whether in range, speed, or power, her weaponry vastly outclassed modern naval artillery.

”Wisdom Cubes significantly enhance our combat abilities, boosting both weapon power and hull durability.”

Belfast explained.

”Hm...”

Setsuna pondered.

”So, essentially, they’re ability amplifiers for shipgirls?”

Their weapons only appeared to be antiques.

For example, Richelieu’s 45-caliber 380mm main guns, Belfast’s 533mm torpedoes, or the single-wing propeller planes on carrier shipgirls—all were deceptively vintage in appearance.

Wisdom Cubes greatly augmented the energy levels of these weapons, making their actual destructive power far greater than they seemed.

”You could think of it that way, but we were born from Wisdom Cube technology. Shipgirls and the Cubes are inseparable.”

Belfast considered her words before explaining further.

”Fascinating. Truly a magical lane.”

Setsuna’s curiosity about the shipgirls’ Wisdom Cube-based power only deepened.

The Richelieu carried Setsuna and Belfast out into the open sea.

This world was a water-dominated planet, with only small portions of land and scattered islands.

The population was sparse. Beyond the harbor, the islands were either overgrown with dense forests or reduced to ruins.

Given that the Crimson Axis had yet to split from the harbor, Setsuna surmised that this world’s timeline was still in its early stages.

After a few hours, the air around them suddenly grew colder.

Far off on the horizon, storm clouds churned, starkly contrasting the bright skies above the harbor.

”Up ahead is the deep sea where the Sirens appear.”

”For safety, we shouldn’t get too close, or it’ll become troublesome.”

Belfast cautioned.

”Got it.”

Leaning on the railing, Setsuna gazed into the distance. Strange black warships patrolled the sea, their silhouettes ominous and otherworldly.

Among them, a humanoid Siren with blue skin was staring back at their ship.

These must be the shipgirls’ enemies.

”How long have you been fighting the Sirens?”

”I can’t quite remember. The harbor has been at war with the Sirens since I was born.”

Richelieu thought for a moment.

”Three years? Five years? Maybe longer. We’ve fought countless brutal battles, trying to eliminate each other completely.”

”But over time, we realized neither side had the strength to deliver a decisive blow. We couldn’t penetrate their deep-sea territory, and they couldn’t breach the harbor. So, we’re at a stalemate.”

”Are the Sirens that powerful?”

”They’re extraordinarily strong. We’ve rarely gained the upper hand in large-scale naval battles. It seems they possess some unknown technology.”

Richelieu paused in thought.

”Our discussions have led us to conclude that the power of this world alone is insufficient to defeat the Sirens.”

”That’s why I hope you can bring advanced technologies or magic from other worlds to help us overcome this enemy.”

The final stop on Setsuna’s tour of the Azur Lane world was their research facility.

At Setsuna’s request, Belfast and Richelieu brought him to see the Wisdom Cube.

At a small shop in a corner of the harbor, Setsuna was greeted enthusiastically by a green-haired shipgirl with cat-like ears.

”Commander, are you here to buy some crates, meow?”

She wore an ill-fitting navy uniform, and her rigging resembled a massive crane. Her oversized sleeves were stuffed with wrenches, pliers, and other random tools.

This was Akashi, one of the few repair ships in the harbor.

She wasn’t much of a fighter; her main duties involved repairing other shipgirls and overseeing the harbor’s research activities.

In her spare time, she also sold refurbished crates—turning blue gear crates into purple ones and purple ones into gold.

”If you didn’t get anything in your ten-pull, it’s just bad luck! The drop rates are perfectly fine.jpg.”

”He’s a guest of the harbor, not the Commander.”

Belfast reminded her.

”If you buy something, Akashi will call you Commander, meow~”

Akashi’s peculiar speech patterns and slightly shady demeanor made her seem like a bit of a con artist.

”Oh? What do you sell? Is it just crates of paint?”

Setsuna glanced at the counter.

”Ship fuel, coolant, cannons, planes, torpedoes—everything a shipgirl might need, meow!”

Akashi pulled out a pile of miscellaneous items, most of which were only useful to shipgirls.

Even if Setsuna bought a WWII fighter plane, it would just be a relic to anyone outside the shipgirls.

”Do you have Wisdom Cubes?”

Setsuna cut straight to the point.

”Wisdom Cubes? Those are for research purposes and not for sale, meow.”

Akashi paused, glancing at Richelieu and Belfast. After scratching her ears and thinking for a moment, she added:

”If the Commander really wants to see one, I can show you—but don’t mess with it! Wisdom Cubes are very precious, meow.”

She opened a hidden door behind the shop and led them through a maze of corridors to a laboratory-like space.

The 300-square-meter room was filled with strange equipment. Some devices resembled laser cutters, others looked like X-ray machines.

Stacks of documents littered the tables.

Setsuna flipped through a few pages, finding mostly experimental data on military equipment.

The Azur Lane world’s tech tree was hilariously skewed—almost entirely focused on military advancements.

After all, with only around 500 shipgirls, they had no need for agriculture or light industry.

Squatting in front of a safe, Akashi fiddled with it for a moment before the lock clicked open, revealing a black box inside.

She retrieved a key, opened the box, and carefully placed a translucent blue cube on the table.

”This is a Wisdom Cube, meow.”

”Creating one is incredibly difficult—it takes a lot of resources and time. The harbor has stopped making new cubes; this is the last one, meow.”

”What were you using them for before?”

Setsuna asked curiously.

”To make Bulins.”

Richelieu answered on Akashi’s behalf.

”Regular shipgirls can’t be directly summoned with Wisdom Cubes; they require real-world warships as their basis.”

”But Bulins only need a small amount of resources and a Wisdom Cube to be created. We produced many Bulins to help build the harbor.”

”Now that we have enough Bulins and our resources are limited, we’ve stopped making new cubes.”

”Ah, I see.”

Setsuna nodded in understanding.

”Based on my research, Wisdom Cubes are essentially perpetual motion machines with limitless energy. They power shipgirl rigging and materialize human cognition into physical forms.”

”They also significantly enhance shipgirls’ physical abilities. Isn’t that amazing, meow?”

Akashi boasted, hands on her hips.

”If the Commander wants to buy it, I can give you a friendly discount—30 million Yen or the equivalent in crude oil!”

”...”

Belfast and Richelieu stared at her as if they’d seen a ghost. ”Is it really that expensive?”

”...”

Setsuna didn’t respond. Instead, he fixated on the Wisdom Cube, sensing an immense energy within.

The last Wisdom Cube—an ultimate technological achievement of the Azur Lane world.

Judging by Akashi’s protectiveness, its value was incalculable.

Compelled by an unknown impulse, he reached out and picked it up, turning it over in his hands.

The cube felt cool to the touch and emitted a faint glow.

”Don’t drop it, meow!!”

Akashi warned nervously.

Suddenly—

Swish!

The Wisdom Cube emitted a blinding light, dissolving like liquid into Setsuna’s palm.

A surge of immense power coursed through his body.

Overwhelmed by the energy, his vision went dark.

”???”

As he lost consciousness, a thought struck him:

What had the system compensated him with after throwing him into the Stone Age due to a bug?

”Significant enhancements to mental strength and physical compatibility,” it had said.

So he could handle and master the unique energy systems of various worlds—whether Wisdom Cubes, Honkai Energy, Magic, Originium Arts or Spiral Power.

Had he unconsciously overlooked this compensation until now? Was it finally activating?

Would he become a shipgirl—or rather, a shipguy?

Akashi, seeing the cube disappear, let out a panicked ”Meow!” and pounced on Setsuna’s unconscious body.

”Ahh! I knew I shouldn’t have shown it to you! Give me back the cube!!!”