Crossover Shipgirls: Building a Dimensional Empire from Scratch

Arpeggio of Blue Steel World

Over the Pacific Ocean—

Buzz—

As space distorted, a fleet of over twenty starships, led by the Eternal Snowfall, emerged into the world.

Judging by their hulls, nearly all were battleships or aircraft carriers—large-scale warships.

When venturing out, the fleet executed an advanced shipborne shipgirl tactic: smaller shipgirls such as destroyers and cruisers remained inside the hulls of larger shipgirls, ready to sortie at a moment’s notice.

Inside the bridge of the Eternal Snowfall, Setsuna was surrounded by several Sakura Empire shipgirls.

The little loli Nagato leaned against the window, gazing at the distant ocean.

Amagi and Musashi sat by the main console, scribbling on the holographic interface, seemingly deep in thought.

Yukikaze, Ayanami, Fubuki, and several other small shipgirls were also gathered inside the cabin.

This was the first time Setsuna had taken so many Sakura Empire shipgirls on an expedition.

Most of them were beast-eared girls, and the swaying tails of Amagi and Musashi made Setsuna itch to reach out and stroke them.

”Tsk, this world’s ocean coverage is almost the same as Azur Lane’s, huh?”

Purifier and Observer looked down from above.

Due to rising sea levels, much of the land in the Blue World had been swallowed by the ocean, leaving humanity to survive on higher-altitude inland areas.

According to their scans, ocean coverage had already surpassed 85%, making it essentially a marine planet.

At the same time, clusters of black-and-red battleships could be seen patrolling the sea surface aimlessly.

”That’s the Fleet of Fog? They seem smaller than the battleships we built.”

”Feels like I could blow them up with a single shot.”

Observer commented with a glance.

”Those are mass-produced models, don’t mind them. The Fleet of Fog’s classification system differs from ours.”

Setsuna explained.

Ships like Kongou, Hiei, Kirishima, and Haruna were considered cruisers in Azur Lane, while Nagato, Mutsu, Bismarck, and Prince of Wales were categorized as battleships.

However, in the Fleet of Fog, all of them were classified as ”Great Warships.”

Above them were the two ”Super Battleships” of the Fleet of Fog—Musashi and Yamato.

Different ship classes had varying access to Super-Graviton Cannons and Klein Fields, while most mass-produced Fog ships only carried conventional artillery and torpedo weaponry.

”Ho~~~ well then, never mind.”

Observer hummed as she looked around but didn’t spot any Fog shipgirls among the mass-produced units.

She had no interest in cannon fodder—she only wanted to capture a genuine alternate-world shipgirl for study.

”Master, do you have a strategy for conquering this world?”

Amagi asked. As the strategist of the Sakura Empire fleet, she quickly began offering suggestions:

”Based on the three objectives you proposed, I recommend first establishing contact with the local humans to understand the current state of this world.”

”Additionally, the protagonist of the Blue World, the submarine shipgirl known as Iona, should be in Yokosuka Harbor. Perhaps we should meet her first?”

”Mhm.”

Setsuna nodded. Entering a new world, the first step was naturally to find the main heroine.

The I-401 was a Fleet of Fog submarine that had been captured by humanity years ago and was kept at the Yokosuka Naval Academy for research.

The current timeline was still early—Chihaya Gunzou was probably still playing in elementary or middle school.

This was a good opportunity to abduct the little shipgirl and use her to establish contact with the Fleet of Fog.

Shua—

The fleet quickly engaged their propulsion engines and set course westward.

Along the way, they spotted numerous patrols of mass-produced Fleet of Fog warships. Humanity in this world had been completely trapped on land.

All maritime trade between nations had been severed. As for air transport... since this world had yet to develop spaceflight technology, aircraft were likely to be shot down by the Fleet of Fog as well.

Before long, the outline of the island nation appeared on the horizon.

”Their territory has been heavily submerged too, huh?”

As they drew closer, Setsuna noticed that the country looked quite different from his impression.

The rising sea levels had fragmented the islands into scattered remnants.

Suddenly—

”Everyone, be alert.”

Amagi’s expression turned serious as she activated the holographic radar, displaying a screen filled with bright red dots.

”Commander, we’ve detected a large-scale naval battle ahead.”

”It looks like the Fleet of Fog is attacking a human fleet!”

”?”

Setsuna blinked in surprise.

”A naval battle? The humans still have the strength to fight the Fleet of Fog at sea?”

He activated the detector and deployed several carrier-based aircraft.

Focusing on the battlefield—

About 30–40 nautical miles ahead, a crescent-shaped formation of over fifty black-and-red Fog warships was encircling a smaller human fleet.

The human fleet consisted of only twenty to thirty vessels, mostly smaller cruisers and destroyers.

They had formed a ring formation around a slightly larger white transport ship, guarding it tightly.

That transport ship must have been carrying something highly valuable, as the entire fleet was shielding it at all costs.

However, the Fleet of Fog had both superior numbers and firepower.

Each volley shattered the enemy’s bridges, turrets, or, in the worst cases, punched gaping holes into their hulls, allowing seawater to rush in.

Before long, over half of the escort ships had been reduced to wreckage.

At the center of the Fleet of Fog formation was a dark-red heavy cruiser. Its deck housed hundreds of missile launch silos and a disproportionately large main cannon.

Standing at the bow was a blue-haired girl in a white dress, her high ponytail swaying as she watched the distant fleet with a look of contempt.

”Takao?”

Setsuna recognized the heavy cruiser shipgirl of the Fleet of Fog.

Then it dawned on him.

”The humans are making a move, and the Fleet of Fog is intercepting them… This setup…”

”Are they transporting vibration warheads?!”

In the Blue World, to counteract the Fleet of Fog’s Klein Fields, the island nation’s scientists had developed a specialized weapon—the vibration warhead.

However, they couldn’t mass-produce them domestically and had been trying to transport them to the Eagle Union.

They hoped this weapon would help them defeat the Fleet of Fog once and for all.

In the original story, their attempts had failed multiple times, and it was only when the protagonist was assigned a similar escort mission that the major events of the plot were set into motion.

”Quick, all units listen up!”

Setsuna immediately issued orders.

”Capture that transport ship. If we get a sample of the vibration warhead, it will save us a lot of trouble later.”

”Take down the Fleet of Fog and Takao as well. Since we’ve run into them, not a single Fog shipgirl is allowed to escape—capture them all.”

”…”

Buzz—

The fleet immediately accelerated, dispersing as they dove toward the ocean below.

At the heart of the battlefield—

Takao stared coldly at the battered human fleet struggling to hold out.

Their determination was more tenacious than expected.

However, under the absolute superiority of the Fleet of Fog, all they could do was delay their inevitable defeat by a few minutes.

”It’s time to end this.”

Seeing that most of the enemies had been eliminated, she raised her hands, an energy wave surging across her hull.

Ka-ka-ka—

The deck and bridge of the warship split apart, revealing a black sphere about four to five meters in diameter, hovering in the air like an orb of darkness.

Super-Graviton Cannon.

This weapon didn’t rely on traditional turrets and barrels to fire energy. Instead, it constrained heavy particles and released gravitational waves to obliterate its targets.

Buzz—

Takao’s Super-Graviton Cannon began charging in mid-air, growing larger and trembling slightly.

Even the surrounding space seemed to ripple.

The humans on the transport ship felt a deep sense of dread.

If that attack hit them directly, not only would the vibration warheads be lost, but the entire ship would likely be vaporized in an instant.

Suddenly—

Shua—!

Boom—!

A vast shadow fell over the sky.

Towering starships blotted out the sun as several positron fortress cannons fired down from the Eternal Snowfall, obliterating the encircling mass-produced Fog warships.

Boom—!

The high-energy beams struck the ocean surface, instantly creating a thick veil of white steam that engulfed the entire battlefield.

”What the hell?!”

”Does the Fleet of Fog have spaceships now?! No... wait... they’re attacking the Fleet of Fog?!”

The humans were left dumbfounded.

Even Takao momentarily forgot about firing her Super-Graviton Cannon, staring blankly at the sky.

The starships above had familiar designs—some resembled battleships, others aircraft carriers—but she had no idea where they had come from.

Then—

Clank, clank, clank—

The bottom hangar of the Eternal Snowfall opened.

A Siren girl, perched on an octopus-like rigging, descended. Beside her floated a twin-tailed girl in a sailor uniform, sporting oversized glasses.

Behind them, a hundred mass-produced Siren units were deployed, quickly launching a boarding assault on the human transport ship.

”Are you Fog too...? No, I don’t recognize your model...”

Takao furrowed her brows as she observed Observer and Purifier.

Neither of them had manifested their hulls, and their ship rigs were unlike anything she had ever seen.

”No, we’re Sirens. You can think of me as another world’s version of the Fleet of Fog.”

Observer clapped her hands, leading the Sirens as they surrounded Takao.

”Come on, let me see how you differ from Azur Lane’s shipgirls.”

”Be good and let me check~~~!!”

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