Crossover Shipgirls: Building a Dimensional Empire from Scratch

After a brief introduction to the shipgirls, Setsuna brought the five Siren girls back to the naval base.

Richelieu, Taihou, Artoria, and Tohru all observed the unfamiliar ”partners” with a mix of curiosity and caution. While outsiders had little understanding of them, even the shipgirls knew relatively little about the Sirens.

”So, can you tell me what you’re capable of and if you have any specific needs?”

Setsuna sat behind his desk, looking at the Sirens. It was time for a preliminary assessment of the newcomers.

Purifier, as usual, acted overly familiar, plopping into a chair and taking the opportunity to tease Yukikaze.

The other four Sirens, however, stood in a row, silent and motionless.

”Here, as long as your requests aren’t too excessive, the Commander will do his best to accommodate you. This includes preferences for your dormitories, meals, or any activities you’d like to pursue,” Richelieu interjected.

”However, you must avoid conflicts with others and refrain from disrupting anyone else’s daily life.”

Welcoming new members to their settlement, especially those from different species, required careful handling. It was critical to understand their needs—be it living arrangements, dietary habits, or personal goals—and ensure they were properly integrated. This principle applied to shipgirls, ordinary humans, dragons, heroic spirits, and now Sirens.

The Sirens exchanged uncertain glances, their expressions hard to decipher.

For beings like them—created and raised as machines of war on the ocean—concepts like hobbies or personal needs were entirely foreign. Their lives had revolved solely around battles with shipgirls.

”I don’t know. We don’t really need anything,” replied a soft voice after a pause.

The speaker was Compiler, dressed in a white dress, her pale skin making her seem almost ethereal. Among the group, she appeared to hold the highest rank.

”What about food? Is there something you’d like to eat?” Artoria asked casually, snacking on some treats.

”We can absorb energy from the ocean. Technically, we do not require sustenance,” Compiler answered in an even tone.

”Then where would you like to live? In the city? Or here at the naval base with the shipgirls?”

”Uh, and don’t say you want to sleep in the Commander’s quarters. Richelieu and I are already taking up all the space.”

Taihou asked again.

”Anywhere is fine. We can even float at sea indefinitely.”

The response was cold and indifferent.

”Do you need to replenish ship fuel or cooling fluids?”

”No need.”

”Would you eat Stargazing Pie or Tohru’s Chaos Cuisine?”

”No.”

”…”

This drip-feed style of conversation left the shipgirls at a loss for words. Aside from Purifier, the other Siren girls exhibited minimal emotional fluctuation. They answered questions mechanically and didn’t engage in playful banter like the shipgirls did. Their demeanor revolved solely around combat and tasks.

”Uh…”

Setsuna tapped his forehead thoughtfully.

”How about this? I’ll have a small harbor built near the naval base just for you. You can temporarily stay there.”

”Some of the younger shipgirls are still a bit wary of you, so living together isn’t ideal for now.”

”I’ll provide docks, repair facilities, dormitories, and a bathhouse—everything modeled after the standards for the shipgirls at the port. If you need anything extra, just let me know.”

”…”

The Sirens processed his words for a moment, as if deliberating their meaning. Then, in unison, they nodded.

”Thank you.”

”Now, can you tell me what skills or abilities you have? In the future, we might need to coordinate in battles against enemies from other worlds.”

”You can think of me as an extra-large battleship. Bigger than Yamato or Musashi, and I could take on five—no, ten of them by myself.”

Purifier casually boasted while ruffling Yukikaze’s hair.

”If you modify me into a starship, I’ll definitely be the strongest in the fleet.”

”!!!”

Richelieu suddenly felt a sense of crisis, her instincts telling her that Purifier wasn’t exaggerating.

”My primary role is to observe the shipgirls and the development of the port. Here, my objective is to observe you, Commander, and your civilization.” Observer explained calmly.

”As for my abilities... I can perfectly mimic any shipgirl.”

As soon as she finished speaking, a flicker of electromagnetic interference rippled across her body, making her form shimmer and blur.

Within a minute or two, the distorted figure began to stabilize and take shape.

Standing before them was a shipgirl who looked exactly like Richelieu, down to her attire and mannerisms.

”Commander, this is my ability.”

Her tone perfectly replicated Richelieu’s cool and serious demeanor, making it nearly impossible to tell the real one apart from the copy.

”I can analyze the data I observe and simulate the appearance, voice, and even the rigging of other shipgirls.”

”What kind of absurd ability is this?! Change back right now!”

Richelieu looked at the perfect replica of herself and instantly panicked, rushing over to grab Observer’s shoulders and shaking her.

”Can you mimic other people? Like Tohru or Jeanne d’Arc?”

Setsuna grew curious and pointed toward the dragon maid and Jeanne d’Arc.

”No, they come from another world, separate from mine.”

”This ability is limited to shipgirls,” Observer explained as she reverted to her original form.

”Interesting...”

Setsuna mused, realizing Siren technology was even more fantastical than that of the shipgirls. He no longer bothered trying to understand how they managed such feats.

”My specialty is eliminating enemies,” Testifier and Omitter stated curtly, unwilling to elaborate further.

”...”

”I am responsible for the construction of Siren fleets, as well as research into Mirror Seas and other technologies,” Compiler said, her voice devoid of emotion, like a machine.

From what Setsuna recalled from the game, Compiler was indeed the one responsible for the creation of Mirror Seas—a technology capable of generating isolated dimensional spaces. However, arriving in this world early meant that this technology was likely still under development.

”Uh, would you mind sharing some Siren technology with us? Anything at all?”

”After all, we’re all on the same team now,” Richelieu asked, crouching slightly to engage the loli-like Compiler in conversation.

”...”

Compiler remained silent for a moment.

”Requesting permission… Tribunal Authority and higher command are out of contact… Proceeding with autonomous judgment...”

”Confirmed. I can provide the manufacturing technology for mass-produced and Executor-class Siren warships,” Compiler stated as she projected a jellyfish-shaped rigging, retrieving several storage-like devices and handing them to Richelieu.

When opened, they contained hundreds of pages of incomprehensible schematics and text.

Setsuna observed that Compiler seemed to be the researcher among the Sirens.

”What’s this?” Akashi looked baffled as she examined the materials, unable to decipher the Siren data.

”The Siren fleet is divided into three tiers,” Purifier began, casually explaining to the shipgirls.

”We, the Elite Sirens, are the highest tier. We possess physical bodies, independent thoughts, and consciousness.

”Below us are the Executors, such as Explorer, Tracker, and Oceana. They’re weaker than us and can be controlled to some extent by our thoughts.”

She paused, then continued, ”The lowest tier consists of the mass-produced ships. Those are the cannon fodder you encounter all the time—carriers, battleships, cruisers, destroyers, and so on. Both we and the Executors can control them with a single thought.”

”What she’s provided you with is the method to create those last two tiers of Siren warships.”

”Uh…” Setsuna considered this for a moment.

”So, basically artificial intelligence warships?”

High-level Sirens controlled Executor-class Sirens, and the Executors commanded vast numbers of mass-produced ships. This hierarchical command system was reminiscent of AI-based armies from certain fictional works.

”You could put it that way, but we use consciousness, not programming,” Purifier clarified, scratching her head.

”So, we can use this technology to churn out a fleet of unmanned warships?!” Setsuna’s realization dawned.

If the Bulins were versatile workers, then the Executor-class Sirens were like military-grade Bulins, capable of commanding mass-produced warships in battle. Lacking independent will and cheap to produce, they could be sacrificed without concern for losses.

Siren expertise, after all, lay in overwhelming enemies with sheer numbers.

”This feels like it could complement us well...” Enterprise’s eyes lit up.

”For large-scale battles, having some mass-produced Siren warships on our side could be handy.”

Shipgirls excelled in individual combat, but with the port’s limited roster of five or six hundred, they could easily be outnumbered in large-scale conflicts.

Incorporating Siren unmanned ships into their forces could enable the creation of hybrid fleets consisting of elite shipgirls supported by a massive swarm of expendable warships. As long as resources and production capacity were sufficient, they could drown the enemy in numbers.

”Hmm…” Bismarck furrowed her brow in contemplation.

”Could this mean we’ll have a combined port-Siren fleet in the future? That’s… quite the novel idea.”

In a sense, Sirens were also shipgirls, though their ship designs and technological philosophies were fundamentally different.

The image of Azure Lane shipgirls leading an army of Siren warships into battle was something they had never dared to imagine before.

”Of course, while we’re at it, let’s recruit the Fleet of Fog and Abyssal Fleet too,” Setsuna quipped, jotting down his ambitious idea in a notebook. ”Then we can form an interdimensional shipgirl coalition.”

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