Crossover Shipgirls: Building a Dimensional Empire from Scratch

Tokyo Bay, Offshore.

When the towering forms of two armored aircraft carriers, accompanied by a battleship and two cruisers, emerged over the horizon, the entire nation was thrown into upheaval.

Their sheer size dwarfed the ironclads and armored cruisers in the harbor, the disparity like that of mountains towering over hills. The red-and-gold eagle banner billowed in the wind, drawing every gaze.

At this time in Earth’s history, even battleship technology hadn’t fully matured, making these aircraft carriers appear as if they were otherworldly constructs.

The port and its surrounding areas were packed with onlookers, along with coastal guards working hard to maintain order.

People stood on tiptoes, straining to catch a glimpse of the mysterious fleet.

Magnificent. Enormous. Oppressively powerful.

Unlike the Imperial Navy’s monotone black ironclads and hastily constructed wooden warships, the Azure Lane shipgirls’ fleet had a stunning appearance.

Their designs retained the aesthetic of World War II-era warships but had undergone significant modern modifications.

Richelieu, with her pristine white hull trimmed in gold, double-tiered command tower, and immaculate deck, looked like a work of art rather than a battleship.

The two armored carriers, Taihou and Illustrious, displayed a more rugged aesthetic, with their decks bristling with aircraft of unfamiliar make and model.

”Hmm, their navy feels rather... nostalgic,” Belfast remarked as she eyed the torpedo boats and ironclads in the harbor.

”Reminds me of a certain unrefined pirate in the Royal Navy—someone so uncouth that many don’t even acknowledge her as one of us,” she added with a faint smirk.

”You’re talking about that sailing ship, right?” Setsuna chuckled.

While the magical sailing ships of certain worlds might rival steamships, this navy clearly lacked the ability to challenge higher-tier technology.

The fleet slowly docked.

Standing on Richelieu’s deck, Setsuna scanned the crowd gathered to greet them.

Due to the nation’s economic underdevelopment during this era, most of the people were quite short, their stature a clear sign of malnutrition.

Even the coastal guard commander, who appeared to be the official representative, stood a full head shorter than Setsuna and had to look up to meet his gaze.

Fear. Confusion. Anxiety. Shock.

The crowd’s expressions were a complex mixture of emotions.

For older observers, the scene dredged up memories of a similar event that occurred some fifty years prior.

Back then, Matthew Perry, commander of the East India Squadron of the United States Navy, had led four warships to Edo Bay, using force to compel the ruling shogunate to open the nation to trade.

At the time, the black ironclad warships of Perry’s fleet were the first of their kind that the Japanese had ever seen, exposing the massive technological gap between Japan and foreign powers.

This culminated in the signing of Japan’s first unequal treaty with Western powers, the Treaty of Peace and Amity, which marked the end of the country’s isolationist policies and ultimately contributed to the downfall of the shogunate.

This event became known as the Black Ships Incident.

Today was eerily similar.

However, Setsuna’s fleet evoked an even greater sense of awe. Aircraft carriers were creations far beyond the comprehension of this era.

The gathered crowd could only silently pray that the visitors harbored no ill intent.

”Commander, I feel like we’re the foreign powers now,” Illustrious quipped.

”We absolutely are,” Setsuna admitted with a nod.

”Why didn’t I think of this sooner? Being a colonial power feels amazing!”

”In the future, we should aim to become an interstellar hegemon, forcing the natives of other worlds to sign unequal treaties,” he added with a sly grin.

Escorted by guards, Setsuna and his shipgirls made their way ashore and headed toward a palace constructed in traditional Japanese style.

The building resembled a fortress, surrounded by moats and high walls, exuding a commanding presence.

This was Nijo Palace, the administrative center of the shogunate and the residence of the shogun—a symbol of national authority.

After traversing a maze of corridors, they arrived at the main hall.

Seated at the center was a middle-aged man wearing a yellow lacquered ceremonial robe and a crown. Beside him stood an older man dressed in black formal attire.

Following protocol, attendants bowed low before respectfully withdrawing.

”Is that the shogun and the emperor?”

Setsuna glanced at the two figures but made no effort to bow or greet them.

Nearby, Taihou whispered, ”Why are these locals putting on such a show? It’s just pomp and ceremony…”

”May I ask who you are?”

The two dignitaries turned their gazes toward Setsuna and the shipgirls.

The newcomers, all wearing black-and-red military uniforms with identical insignias, appeared to belong to a unified organization or nation.

Given the terrifying fleet docked at the harbor, their strength was undeniable.

”We are the Starsea Alliance Expeditionary Fleet. We’ve already informed you of our arrival.”

”We come from another world to discuss cooperation.”

With a snap of his fingers, Setsuna signaled Richelieu, who stepped forward and produced a document.

Bang!

Setsuna strode up and slammed the document onto the table before the shogun and emperor.

”On behalf of the Starsea Alliance, I demand your subjugation. From this moment forward, your nation will become a tributary state under our alliance.”

”All agricultural, industrial, and commercial production will be managed by us, with annual tribute quotas to be fulfilled.”

”All military forces are to be disbanded, except for essential security units.”

”These are the additional clauses...”

The two men stared at the document and then at the young man before them, utterly stunned.

Although young, Setsuna exuded an intimidating presence.

The shogun cautiously flipped through the document.

It detailed the yearly tribute requirements, including quotas for minerals, timber, textiles, agricultural products, and more.

The tribute percentages ranged from 20% to 50%. Agricultural contributions were relatively modest, but the extraction rates for metals and coal were significantly higher.

The terms showed a precise understanding of the nation’s productive capacity and societal structure, extracting resources without entirely collapsing the local economy—but effectively crippling their ability to develop further.

”If cooperation is your aim, this treaty seems… excessive,” the emperor hesitated, carefully choosing his words.

”This is the final offer—no negotiation,” Setsuna replied coldly, tapping the table for emphasis.

”You have three days to decide. If I do not receive a favorable answer by then, my fleet will initiate an attack.”

Swish.

With that, Setsuna turned on his heel and left, the shipgirls following in tow.

The remaining officials were left slack-jawed, while cold sweat dripped from the brows of the emperor and the shogun.

The shogunate was in turmoil.

The fleet’s arrival had caused an upheaval even greater than the Black Ships Incident fifty years earlier—and in some ways, it was far more outrageous.

At least back then, the Black Ships were led by Matthew Perry, a recognizable admiral from the United States East India Fleet. Everyone knew he represented a Pacific nation, and his demands were relatively mild: opening trade ports, permitting consulates, and granting most-favored-nation status.

But this fleet? It wasn’t even from Earth, let alone tied to any known nation. Their technology was entirely alien. If not for Setsuna’s humanoid appearance, the shogunate might have suspected them of being extraterrestrials.

Their demands were also far more ruthless.

”Acknowledge the Starsea Alliance as your suzerain. All production, economic activities, and trade will be managed by the Alliance.”

”An annual tribute of resources must be paid. Beyond this, the Alliance will not interfere excessively with your internal affairs.”

After the shogun finished reading the document aloud, the court ministers exchanged uneasy glances.

It was brutal—far too brutal.

This was no simple request to open ports or cede territory. It was a direct order to bow down and serve.

The treaty didn’t even bother with trade—why trade when you could just take?

Signing it meant turning the nation into a resource colony under the Alliance, stripping it of any self-determination or prospects for development.

”Surrendering without resistance and signing such a treaty will provoke national outrage,” said a military officer.

”As soldiers, we must put up some resistance for the sake of our honor.”

”Then who’s going to fight?”

The shogun’s mind flashed back to the massive aircraft carriers, their size dwarfing cities. He shuddered.

”The army?”

”What about launching a surprise attack on their ships? Could we seize one of them?”

”Let the navy idiots do it! This isn’t our jurisdiction!” shouted the army general.

”Tokyo Bay is your defense zone! You go!” the navy officers snapped back, accusing the army of cowardice.

”Cowards!”

”Fools!”

The room devolved into a shouting match as both sides cursed each other’s ancestors.

To suggest using torpedo boats for a boarding assault on aircraft carriers was absurd even by Showa-era standards. If this were two decades later, someone might have actually greenlit such a reckless operation. But in the Taisho era, the military lacked the creativity for such daring stupidity.

The atmosphere failed to reach Showa-era recklessness.

”Direct confrontation is unfeasible. Perhaps we could try to win over the fleet commander instead?”

The shogun rubbed his temples, trying to calm himself.

”Let’s arrange another meeting and see if there’s room to negotiate the terms of the treaty.”

The next morning.

Yawning, Setsuna emerged from his cabin aboard Richelieu.

Down by the docks, a commotion of drums and trumpets filled the air.

A military band, clad in ceremonial uniforms, was performing near the port, while an official accompanied by two squads of attendants waited respectfully.

”Commander, envoys from the shogunate have requested an audience,” Belfast’s voice came through the communicator.

”They claim it’s an urgent matter.”

”Oh?”

Setsuna stretched, shaking off his drowsiness, and proceeded to the reception hall.

In the hall, the shogunate envoy stood with utmost politeness, accompanied by attendants carrying several chests.

”This is a small token of the shogunate’s goodwill,” the diplomat said, clapping his hands.

The attendants opened the chests, revealing gold, silver, and jewelry—clearly the fruit of years of savings.

Setsuna glanced at the offerings but neither accepted nor rejected them, merely nodding.

”Additionally, we deeply regret our inability to properly welcome you upon your arrival.”

”If you wouldn’t mind, we’d like to invite you to tour the city this evening, followed by a banquet in your honor.”

”The Ichiban District is quite popular among locals and foreigners alike. Would the general be interested?”

The diplomat’s demeanor was impeccable, exuding the characteristic humility of the Japanese.

”Ichiban District?”

Richelieu, Belfast, and Illustrious all looked puzzled.

”Kabukicho,” Taihou interjected, the word rolling off her tongue with a smirk.

She nudged Setsuna, whispering mischievously, ”Commander, you’re not planning to visit such places, are you? Isn’t having me enough?”

”Not interested.” Setsuna dismissed the offer flatly.

”I’m not like some Cao Cao figure who starts every visit by asking, ’Are there any courtesans in the city?’”

”I have no interest in your diplomatic rituals, your high-ranking officials, or your local customs. All I want is a simple answer: will you accept or reject the treaty?”

”Don’t overthink it, and don’t waste time with unnecessary gestures. They’re meaningless.”

”Please return and relay this message to the shogunate: think carefully about your decision.”

The envoy froze, the carefully rehearsed speeches stuck in his throat.

From start to finish, Setsuna’s stance was resolute—he had no intention of negotiating.

Swallowing his pride, the diplomat hesitated, then asked hoarsely:

”Why… why did you choose us?”

”Japan’s resources are scarce. Even as a tributary, what we can offer is limited. If you’re seeking overseas markets, wouldn’t other nations be more suitable?”

”You’re close, so you’re first.”

Setsuna stood, signaling the meeting was over.

”Every nation on this Earth will eventually fall under the Alliance’s dominion. Whether it’s the British Empire or tribal chiefs in the African savanna, they’ll all become tributaries.”

”Miners will mine, farmers will farm, fishermen will fish—

You all have a bright future ahead.”