The Siren Executors moved with incredible speed.
With absolute firepower superiority, they swept through the area with little to no resistance.
In the Arpeggio world, humanity had focused nearly all its resources on fighting the Fleet of Fog. With maritime transport completely cut off, naval warfare between human nations was nonexistent.
As a result, land-based garrisons were minimal, and the troops lacked strong combat resolve.
When faced with the overwhelming surge of Siren shipgirls, the defenders attempted a token resistance using small arms, mortars, and howitzers.
But they quickly realized—
Their weapons had zero effect.
Even when tanks were brought in for close-range attacks within mere dozens of meters, the Executors merely staggered from the impact.
And in response—
Their ship cannons would teach the natives the true meaning of firepower.
Meanwhile, the looming starships above had yet to intervene.
Just looking at their main cannons was enough to instill the fear that, should they fire, the entire port—or even the entire city—would be reduced to ashes in an instant.
Thus, one hour later—
Setsuna stood in the plaza of Yokosuka Port, accepting the surrender of the local garrison commander.
"We will immediately withdraw all forces from this area. All personnel will disarm and cease resistance."
"We intend to retreat northwest to Kawasaki City. Please allow your troops to open a path for us."
A middle-aged man in a white naval uniform bowed slightly toward Setsuna.
He was the same vice admiral who had been fantasizing about an alliance with aliens to fight the Fleet of Fog just moments ago.
He discreetly observed Setsuna and the shipgirls behind him.
It was… strange.
They weren't the stereotypical aliens with oversized heads and glass helmets.
They were humanoid.
More than that—their average beauty was downright terrifying.
The man in front of him looked young, yet carried the unwavering presence of a seasoned commander. His gaze was firm, confident—exuding absolute certainty in his own strength.
"Good. Off you go."
Setsuna nodded, patting the vice admiral's shoulder.
"We will be issuing a formal demand for your government's surrender soon. When you return, make sure to inform them of everything you've seen today."
"And remind the others—don't do anything stupid."
As he spoke, he gestured toward the fleet of starships hovering in the distance and the perfectly assembled Siren Executor troops standing at attention behind him.
"!!!"
The vice admiral shuddered.
Though he was twice Setsuna's age, he couldn't suppress the instinctive tremble in his body.
This was a blatant, undisguised threat.
Demanding an entire nation's submission? Instructing them to remember what they had witnessed today?
What had he seen?
A single Siren Executor capable of wiping out an entire army division and shelling ground forces with warship-grade artillery? There was an entire battalion of them standing behind Setsuna.
Dozens of starships, each capable of obliterating Fleet of Fog warships in a single strike?
As for the part about "not doing anything stupid"…
The message was crystal clear—
Obey every demand. Roll over and be good little vassals.
Forget any thoughts of resisting with their pathetic native military technology. The moment the starships opened fire, it would already be too late.
"May I ask where you're from? What exactly do you intend to do? Are you affiliated with the Fleet of Fog…?"
He asked cautiously.
"None of your business. Now, get moving."
Setsuna had no interest in wasting time talking to insignificant natives. He simply waved him off.
The vice admiral didn't dare press further, fearing that any misstep might make Setsuna change his mind and wipe them out on the spot. He immediately led his troops into retreat.
"We were already being bullied by the Fleet of Fog at sea… and now we have to take a beating from aliens on land…"
"Is there no salvation for this world?!"
...
Once the entire Yokosuka Naval Base had been evacuated, Setsuna and his shipgirls officially took control of the area.
Atop the fortress's main building, the Azur Navy Flag and Starsea Alliance Banner were hoisted high.
The Siren Executors swiftly cleared the port and its surroundings of any remaining personnel, establishing blockade lines along both the coastline and major land routes.
Meanwhile, the Bulins efficiently tidied up the wreckage, working with seamless precision—almost as if they had rehearsed this scenario countless times before.
"Is this… how you wage war?!"
Takao was left dumbfounded.
As a Fleet of Fog shipgirl, she was used to intercepting human fleets at sea, occasionally launching attacks on ports to cripple coastal defenses.
But a full-scale amphibious invasion? This was a first.
The Siren shipgirls weren't just naval combatants—they were ground forces as well.
They were unstoppable.
"We conquered an entire planet in a single day last time. This is nothing."
Purifier scoffed at Takao's astonishment. Fighting weak natives wasn't even fun—she couldn't unleash her full strategic capabilities as a high-tier Siren.
"..."
"Now then, it's time to meet Iona."
"There's still a little shipgirl hidden away here."
Setsuna led his group through the fortress, weaving through passageways until they arrived at an underground dry dock.
There, floating silently in the still waters, was a sleek, futuristic submarine painted in shades of blue.
The surrounding personnel had long since fled, leaving the facility eerily quiet.
The hull bore the identifier: 401.
Even at a glance, it was clear—
This submarine's design was leagues ahead of 21st-century engineering.
I-401, Iona.
The protagonist of Arpeggio of Blue Steel.
Years ago, humanity had fought a desperate battle against the Fleet of Fog for control of the seas.
But their advanced Super-Graviton Cannons and Klein Fields had utterly crushed human navies, leaving them with no choice but to abandon the oceans entirely.
During that conflict, Iona had been intentionally captured.
All her systems had been locked down, and ever since, the Yokosuka Naval Academy had attempted to study her.
But no matter what methods they tried—whether brute force or electromagnetic interference—they couldn't breach her hull.
Nor did they have any idea whether a Fog shipgirl even existed within.
"If we follow the original storyline… Iona should have remained dormant here, waiting for Chihaya Gunzou to accidentally awaken her. But now…"
Setsuna mused to himself, placing his hand against the submarine's hull.
Bzzzt—
A faint static charge pulsed against his palm.
A clear rejection.
Iona had been programmed with a pre-existing order—
She would only obey Chihaya Gunzou.
"Hmm. Do you want me to take her apart and check inside?"
"You do have plenty of Bulins on hand…"
Gudako suggested casually.
"No need. It's just a simple command lock… and we have ways to fix that."
Setsuna smirked, then turned to Mio.
"Can you reset her?"
"Huh? Me, Setsuna?"
Mio brightened at the thought of being useful.
She stepped forward, examining the submarine.
"Hmm… I don't know much about machinery, but if there's a consciousness inside, deleting a single line of memory isn't hard…"
As she spoke—
Shua—
[Ain-Soph: Paradise of Samsara]
With a wave of her hand, the surroundings transformed into a monochrome world of black and white.
The Spirit of Origin unfolded her domain.
Here, she could rewrite reality itself.
Mio stepped forward, phasing through Iona's hull as if it wasn't even there.
Inside the submarine, a white-haired girl in a sailor uniform lay asleep against the control console…
Mio gently reached out and stroked Iona's head.
"Such a cute child…"
Then, she tapped her forehead lightly, releasing a wave of spiritual energy.
For the Spirit of Origin, locating and modifying a single memory was effortless.
"?"
Iona's eyes slowly fluttered open.
Bzzzt—
As her engines hummed to life, layers of blue energy barriers peeled away from the submarine's hull.
Then—
Clank—Clank—Clank—
The ship's exterior shifted and unfolded, transforming before their eyes.
A girl emerged from within—
She wore a blue sailor uniform, black thigh-high socks, and bore silver hair with striking green eyes.
Her appearance was somewhere between a destroyer and a cruiser—sweet, delicate, and undeniably adorable.
"Setsuna…?"
Iona gazed at him blankly, her voice emotionless, almost mechanical.
She had been created as a weapon of war—
Unlike the Azur Lane shipgirls, she lacked rich emotional depth.
Her instincts were to obey orders—nothing more.
"I inserted some information about you into her memory."
Mio explained.
"Mm. From now on, you can call me Commander."
Setsuna ruffled Iona's soft hair.
She was small and incredibly cute—just a little too cold and expressionless.
"401!!!"
Takao gasped in shock upon seeing Iona.
"That's the traitorous 401! The Fleet of Fog's orders are to eliminate this rogue submarine!!"
"..."
"You're… Fog as well?"
Iona immediately identified Takao's origins, her gaze wary.
"Enough, enough—none of that 'traitor' nonsense. From now on, we're all family."
Setsuna gave Takao a firm pat, signaling her to calm down.
"We'll establish a Blue Steel Fleet for you all, set up a naval base, and with Azur Lane and Siren fleets alongside it, we'll have a Three-Fleet Alliance."
"..."
"She… seems older than our submarines."
Musashi mused, glancing at the Azur Lane submarine shipgirls.
A small, red-haired beast-eared submarine girl stepped forward and cheerfully greeted Iona.
"Hello! I'm I-19, a submarine shipgirl. It's nice to meet you!"
Her voice was bright and youthful, but filled with sincerity.
Iona tilted her head slightly, hesitated, then replied:
"…Hello?"
"Can I take a look inside your ship? What kind of weapons do you have? I can show you mine too!"
I-19 asked eagerly.
Among shipgirls, one of the quickest ways to build trust was by sharing details about their ships.
"Understood."
Clank—
Iona's hull shifted again, expanding and unfolding as she displayed her full arsenal.
"This is everything."
She responded flatly.
Still in pure combat mode, she lacked any real social instincts.
"Whoa?!——"
The shipgirls were stunned by what they saw.
The sheer amount of equipment on a single submarine was outrageous.
Torpedo launch racks, anti-air guns, and even a 50-caliber 140mm naval cannon mounted on the stern.
"You're really a submarine?!"
I-19 blinked in disbelief.
"You shouldn't think of her as a normal submarine."
Setsuna chuckled, ruffling I-19's ears.
"Right now, Iona hasn't even been upgraded with a Super-Graviton Cannon yet. Once she reaches her final form, she'll be a fully-fledged Underwater Assault-Type Mobile Battlecruiser!"
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