Crossover Shipgirls: Building a Dimensional Empire from Scratch

After confirming their next conquest target, Setsuna took advantage of the cooldown period for his spatial-piercing skill to distribute detailed information about the world of KonoSuba to his expeditionary companions.

The files included everything from factions and magic systems to enemy power levels.

The data was comprehensive, and the Butterfly Sisters, Fu Hua, Griseo, and the others studied it seriously—it was their first time dealing with a true magic-based world.

Mio and Tohru, on the other hand, didn’t seem to care much. Both were gods in their own right, though Setsuna privately thought that the ”official” goddess Aqua was several tiers weaker than Mio—the latter being more of a knockoff deity in temperament but terrifyingly strong in practice.

Tohru alone could probably make Aqua flee in tears.

Meanwhile, Setsuna continued managing the daily affairs of the Starsea Empire.

Each day, he would inspect the academy for the little lolis and oversee the empire’s interstellar development projects.

Unknowingly, the Starsea Empire had grown into a civilization spanning the cosmos.

Thanks to the fact that, within observable range, they were the only intelligent species in their universe—and with Bulins and Angeloids now mass-produced in vast numbers—the empire’s expansion rate had become exponential.

Every month, millions—sometimes tens of millions—of Bulins and Angeloids were either manufactured or summoned from starbases.

They would then travel hundreds of light-years away to expand imperial territory.

On barren planets, they would deploy colony ships and outposts, mine resources, and build more Angeloids on-site.

Other times, they were sent to vassal universes to develop local resources there.

Supported by over a dozen vassal universes, materials such as alloys, ores, and rare metals were continuously shipped back to Earth and the main starbases.

Even with factories and shipyards running at full capacity day and night, reports of storage overflows were still frequent.

Material abundance was absolute—development no longer suffered from any resource constraints.

As a result, the engineering departments of the Starsea Empire adopted a distinct philosophy:

No compromises. Only perfection. Cost irrelevant.

Whenever they designed something for the Commander or his companions, ”cost-performance” simply didn’t exist as a consideration.

Every aspect was to be executed at the highest possible level.

A few days later—

When Setsuna prepared to review supplies and expedition rosters, a message arrived from the repair shipgirls and Siren engineers.

”Commander! We’ve completed the Strelitzia’s modification, nya~!”

”It’s super strong now!!!”

...

”Ohhhhh—!”

Upon receiving the message, Gudako immediately dragged Setsuna to the engineering sector.

Joining them was the Klaxosaur Princess, curious to see how a mecha similar to her kin had been transformed.

They boarded a shuttle and flew north from the capital to the Eurasian engineering test zone.

Though the region’s latitude was high, climate control made the weather pleasant.

On an open testing platform stood a colossal red-and-white mecha over sixty meters tall, silent and imposing.

From the outside, it retained the Strelitzia’s signature curves and details—the elegant contours, the intricate limb designs, and the iconic spear-shield combination.

”Commander! This is the Strelitzia Custom, MK-I model!”

”Since you’re going on another interworld expedition soon, we mobilized thousands of Colorful Bulins to finish it quickly, nya~!”

Akashi leaped into Setsuna’s arms, rubbing her head affectionately against his chest.

”...”

Setsuna wanted to say that the Strelitzia wasn’t strictly necessary for the KonoSuba expedition.

After all, between the Eternal Snowfall, his human form, and powers like the Taixuan Eminence and Herrscher authority, he could practically sweep the world solo.

Still, it was a heartfelt gesture—and he couldn’t bring himself to refuse.

”Good work.”

He reached out and rubbed the cat-eared girl’s head.

”What about me?!” Observer protested, waving her tentacles. ”I spent days redesigning the blueprints! The Bulins finished in a day and a half thanks to me!”

”Commander, you can’t discriminate against Sirens—”

”Oh, right. Thanks. I’ll have the chefs at the Far East restaurant make something special for you.”

Setsuna reached out and patted the little Observer on the head.

She was quite capable—but sometimes, like a mischievous brat, she loved to tease people just for fun.

”Cough—”

Purifier shot a strange glance at Observer before beginning the formal briefing about the mecha.

”This Strelitzia modification project was mainly designed by Observer, so if you have any questions, Commander, please direct them to her...”

”?”

Setsuna blinked. That sounded suspiciously like an attempt to preemptively shift blame.

”We’ve given the Strelitzia a full modernization overhaul,” Purifier continued. ”It’s now equipped with the most advanced weapons and technologies of the Starsea Empire.”

”It also has an independent power reactor installed—allowing it to operate autonomously. Its new engine can perform short-range faster-than-light maneuvers across interstellar space.”

A holographic interface appeared in front of them as she spoke.

”An FTL Gundam? That’s awesome...” Gudako’s eyes gleamed.

”Furthermore,” Purifier added, ”since Strelitzia is a bio-mecha, it’s fundamentally different from models like Strike Freedom or Barbatos.”

”It’s not purely technological—it’s also influenced by metaphysical factors such as spiritual energy, the pilot’s emotions, and the bond between its operators. Commander, I’m sure you understand what that means?”

Setsuna nodded.

In the original DARLING in the FRANXX, after the Klaxosaur Princess transferred her power to Zero Two, Strelitzia’s strength skyrocketed.

It could even fight in outer space—and its pilots’ emotional bond allowed it to evolve into the bridal-like Strelitzia True Apus form.

Unscientific, but undeniably… mystical.

”So,” Purifier continued, ”we’ve modified Strelitzia to support both single-pilot and dual-pilot configurations. After all, the power of love can be quite formidable. Cough.”

”Who knows, Commander—perhaps you and your co-pilot could trigger some sort of idealistic resonance.”

With that, she remotely opened the cockpit.

”Hm?”

Setsuna didn’t particularly care whether it was a single or dual-pilot setup.

But Gudako and several shipgirls, who had been eavesdropping eagerly, perked up instantly.

”Wait—does that mean we can form a dual-pilot bond with the Commander?!”

”In theory, yes...”

”LET ME TRY FIRST!!!—”

A crowd of shipgirls immediately swarmed together, each volunteering at once, creating total chaos.

”I’ll do it,” the Klaxosaur Princess said softly.

”Since FRANXX mechas were originally derived from Klaxosaur technology, I want to see what kind of transformation you’ve made to it.”

”...Alright, you go first.”

After a moment’s thought, Setsuna agreed.

The two entered the cockpit together.

”?”

The moment Setsuna sat down, something felt… off.

”Uh, Commander… it’s a bit cramped.”

The Klaxosaur Princess shifted slightly in the front seat, turning her head curiously.

Normally, she could pilot a FRANXX unit using her own powers without relying on synchronized physical positions.

Unfortunately, this customized version required proper seating—no shortcuts.

”...”

They were practically pressed together, and considering the awkward posture and the few ribbons casually draped over the Princess’s body… the scene was far from proper.

”Did you mess up the cockpit design?” Setsuna asked.

”No, sir. It was intentional—Observer’s idea!” Purifier declared immediately, throwing her colleague under the bus.

”She said that ’close physical contact between the male and female elements helps Strelitzia unleash its full potential.’”

”Seriously?” Setsuna asked, incredulous.

He had never heard of such a theory.

”I thought it was nonsense—but she swore it was true,” Purifier replied.

”...Drag her out and give her a good beating.”

”Understood~!” Purifier saluted cheerfully.

...

Boom—

Under everyone’s watchful eyes, Setsuna and 01 activated the Strelitzia.

The mecha blasted straight from the ground into the sky, streaking through the atmosphere like a meteor.

”Oh, its speed has improved a lot.”

Setsuna immediately noticed the most apparent enhancement—the mecha’s maneuverability had been boosted by several levels.

It could now rival a small frigate in performance and, thanks to its smaller frame, was even more agile.

”Amazing. It’s much faster than when I first saw it,” said the Klaxosaur Princess in astonishment, closing her eyes briefly as if sensing its energy.

”This thing consumed quite a bit of resources,” Setsuna remarked as he pushed the Strelitzia to accelerate further.

Moments later, the mecha broke into light-speed travel. Outside the cockpit, the stars elongated into bright streaks of light.

An FTL Gundam. In practical space combat, it might not outperform a battleship—but it certainly looked cool.

Click—

Setsuna accessed the weapon systems.

”Commander,” Purifier’s voice came through, ”we’ve made some changes to the Queen Pike. Originally it fired magma energy, which was outdated.”

”We’ve upgraded it into a photon lance. Of course, you can still use it for close combat—its material strength allows it to pierce almost any substance we’ve encountered so far.”

”Oh?”

Setsuna controlled the mecha, drawing the massive white spear.

Compared to the original Strelitzia, the new weapon looked far more futuristic. Its spearhead had been replaced with a glowing cyan alloy.

Charging… Aiming…

BOOM!!!

A torrent of pale-blue energy erupted from the Queen Pike’s tip, shooting millions of kilometers into the void—

—and instantly vaporized a passing comet.

”The Queen Pike’s photon lance can’t match the larger version installed on the Juggernaut,” Purifier explained excitedly, ”but it’s a specialized close-range model—short charge time, high firing rate, perfect for stabbing an enemy right in the face.”

”...”

Setsuna couldn’t help but imagine a close-combat duel ending with a point-blank photon blast. The thought was… oddly satisfying.

”I love it!” Gudako exclaimed without hesitation.

”Make one for me too! Next time I’m in a Gundam fight, I won’t be afraid to brawl anymore!”

”I refuse to believe anyone can block a photon spear at zero distance!”

”Alright, I’ll have a personal version made for you,” Setsuna replied.

He then began testing the other weapons equipped on the Strelitzia.

In its original form, the Strelitzia mainly relied on the Queen Pike for combat. After the modifications, however, its internal systems concealed an astonishing arsenal.

Beep—

With a single command, a pair of armored wings extended from its back.

The design was clearly inspired by the Strike Freedom Gundam.

Mounted across the wings were numerous plasma cannons, micro electric arc blasters, and gamma laser units.

Boom boom boom—

Setsuna unleashed a barrage at a barren planet below, carving several massive craters into its surface.

”Additionally, we’ve installed the Turn A’s Moonlight Butterfly system! You said the Turn A looked ugly, Commander—so we put it on something much cooler instead!” Purifier proudly listed the mecha’s full loadout.

A light tap.

[Activating Moonlight Butterfly System]

Shua—

Brilliant, multi-hued wings unfolded behind the Strelitzia, stretching hundreds of meters wide.

This was the Turn A Gundam’s ultimate weapon—capable of planetary annihilation.

Unfortunately, since the Eternal Snowfall already possessed the Fallen Star Lance and Photoid weapons, which were far more efficient, Setsuna rarely needed to use this system.

”I want it!!!”

”I need it!!! I’ll use it!!!” Gudako shouted, bouncing with excitement.

Following Setsuna around, she always got the leftovers—but even those were god-tier.

He didn’t need mechas anymore, but she absolutely did.

”With this, I can wipe out entire planets! Finally, I can destroy those stupid Singularities and Lostbelts myself!!!”

”...”

”Are you a soup addict or something...?” Setsuna muttered dryly.

...

After piloting the Strelitzia on a few orbits through open space...

”Mm…”

The Klaxosaur Princess shifted uncomfortably in the front seat.

”Commander… it’s a bit cramped…”

”...”

’Cramped’ was putting it mildly, Setsuna thought.

He was already doing his best to keep his composure, but given the awkward cockpit setup—and the Princess’s outfit, which somehow managed to be more provocative than wearing nothing—it was impossible to avoid certain… situations.

”Right, Commander,” Observer’s voice suddenly came through. ”Try activating Strelitzia’s alternate mode.”

”If the male and female elements achieve synchronization, Strelitzia can transform into a far stronger form—Strelitzia Apus.”

”Since the FRANXX mechas were originally designed by the Klaxosaur race, the Princess should be fully compatible. And Commander, since you can harmonize with powers from other worlds, theoretically, the two of you could unleash its full potential.”

”Hm…”

Setsuna thought for a moment.

”That makes sense. Shall we try?”

”Alright.” The Klaxosaur Princess nodded slightly.

Setsuna focused his consciousness into the Strelitzia.

He felt himself merging with the machine—his senses blending with its circuits and frame.

Then, another presence joined his mind.

01—the Klaxosaur Princess.

Their consciousnesses intertwined, and Setsuna’s perspective changed.

Suddenly, he saw her memories as if they were his own.

Sixty million years ago—she led her people, the Klaxosaurs, in battle against the VIRM.

After a brutal war and barely managing to repel a vanguard fleet, they were forced underground to survive.

To prepare for the next invasion, her comrades one by one transformed into magma energy or lifeless war machines—leaving the young princess utterly alone.

She never wanted to live so long. She simply endured, bound by duty—to protect her world.

Years passed in lonely slumber, manipulated humans fought endless wars above…

Until she met him.

Though she rarely showed emotion and seemed cold to everyone, deep in her subconscious, Setsuna could feel her happiness at his arrival.

Partly because he destroyed the VIRM.

And partly… for reasons beyond duty.

”So this is who you really are…”

The Princess, in turn, glimpsed fragments of Setsuna’s mind.

A life full of adventure and laughter—fighting across stars, fusing alien technologies, conquering countless worlds.

Always surrounded by companions, always moving forward.

She felt a faint envy.

”…Is this some kind of mutual memory-viewing embarrassment play?” Setsuna muttered.

Then—

He felt the mecha itself begin to change.

Clank—

Clank, clank—

In the void of space, the 60-meter-tall Strelitzia started to transform.

The power came partly from Setsuna and the Princess, and partly from the machine itself.

Some strange reaction was taking place between them.

The Strelitzia’s legs unfolded.

From its back spread a pair of massive metallic wings, their span rivaling a battleship’s.

The frame expanded exponentially, and a single white horn extended from its head.

Feather-like armor grew to envelop its body.

From the outside, it now resembled a giant bird forged of steel—a bird of paradise.

BOOM—

Setsuna lightly tested the controls.

Every system parameter had multiplied several times over.

Its mobility, defense, and firepower were now on an entirely different scale.

To call it battleship-class would not be an exaggeration.

Even the main cannon atop its horn—untested so far—was said to have once annihilated an entire VIRM strike fleet.

”What the heck is this?”

”Does this thing run on love energy?!”

The shipgirls below were left speechless.

Watching a Gundam transform into this… defied every law of physics. Even accounting for added armor and weaponry, there was simply no explaining where all that mass came from.

”Strelitzia’s special that way,” Observer explained smugly while pinning Purifier to the ground. ”It’s not a purely technological construct—it can draw and convert the pilots’ emotional energy into power. Amazing, right?!”

”I told you! I said that if the male and female elements synchronized, Strelitzia would unlock another mode! Now apologize! Say it!”

”...”

”But is that awkward cockpit position really necessary?” someone asked.

”It’s vital! Full physical contact helps the pilots’ hearts connect!” the little loli declared self-righteously.

”Oh, right, Commander,” Observer continued, ”according to the original story, Strelitzia has another form—the True Apus Mode. But that requires combining the powers of the male pilot, 02, and the Klaxosaur Princess.”

”So, when 02 grows a bit older, you can consider a triple synchronization—uh, I mean, a three-pilot formation.”

”???”

Setsuna froze.

”What kind of R-18 mecha is this supposed to be?!”

—

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