Crossover Shipgirls: Building a Dimensional Empire from Scratch

Only a few minutes had passed since the Guardians and the Pleiades were teleported aboard by the World-class item.

From the moment both sides began fighting, it was a completely one-sided massacre.

Soul Eaters, the Pleiades, Aura, and Mare were all swiftly defeated.

Demiurge was thoroughly rattled.

Something was off.

Even players facing the Pleiades couldn’t take them all down in such a short time.

And the shipgirls’ ”magic” was unheard of.

No, Demiurge couldn’t sense any magic aura from them at all—it was pure technological creation.

Mare and Aura, the two Floor Guardians, were the same.

Demiurge hadn’t even noticed how they went down.

Aura had trapped three Heroic Spirits inside her ”Depiction of Nature and Society.”

But only the three Heroic Spirits came out?

Under the effect of a World-class item, three versus two, and they still won against the two Floor Guardians?!

How was that even possible?!

As the brains of Nazarick, Demiurge rapidly calculated the opponent’s power, and a terrifying scenario began forming in his mind.

Things were completely different from what Lord Ainz had anticipated.

This ship wasn’t manned by weak, defenseless human crew—it was full of monsters on par with, or even stronger than, Floor Guardians!

”Did they already foresee Lord Ainz’s movements and concentrate their forces here, or... does this ship naturally have this level of defense?”

Demiurge analyzed two possibilities in his mind.

Either one was terrifying.

Bang — Crack —

While distracted, Elma charged at him with her trident.

”A dragon?”

Demiurge had killed countless dragons, but he had a bad feeling about this one.

He quickly sidestepped and retreated.

”Shalltear! Help me take her on!”

”Tch—”

Shalltear saw that the dragon girl wore barely any gear and couldn’t gauge her level.

The trident looked plain and simple, hardly a mythic item.

She stepped in front to block.

”Die!”

No words wasted—she thrust her lancet directly.

Crack—

Elma caught the weapon tip between two fingers. It couldn’t budge.

In close combat, Shalltear could suppress even the Sorcerer King, but before Elma, she was like a child.

”Die! Die!!”

Shalltear unleashed a furious flurry of attacks, but Elma blocked everything with just one hand.

”A vampire, huh...”

”I’ve dealt with many before. You’re much weaker than that True Ancestor over there.”

The dragon girl reached out with her other hand and pressed it against Shalltear’s chest—her body instantly froze.

Purify

Fwoosh—

A magic circle lit up on Elma’s hand, and a blinding holy light erupted. Under divine power, Shalltear disintegrated into ashes.

”This scene feels familiar.”

Setsuna remembered how Shalltear got played like this in the original story—ah no, that was Brain.

The gap between Shalltear and Elma might be even greater than the one between Shalltear and Brain.

That seemingly goofy, gluttonous dragon girl was actually on par with Tohru in strength—an honest-to-goodness demigod.

”!!!”

Seeing Shalltear defeated in a single move, Demiurge considered retreating.

The mission had failed. They weren’t a match for this enemy.

In that case, it was better to withdraw early, return to the Great Tomb, and bring this intel to the Sorcerer King.

Maybe Lord Ainz could come up with a way to counter these foes.

”Teleport!”

He waved his hand.

Nothing happened.

”?”

”Space is sealed?”

Demiurge was confused. His own spatial lockdown shouldn’t affect him.

”Spatial seal, disengage!”

Crack—

Crystalline structures in the air shattered.

But the teleportation spell still failed.

”What?!”

The next moment, Demiurge suddenly felt a chill down his spine.

He turned his head—and met Tohru’s gentle, smiling gaze.

The dragon girl’s crimson pupils locked onto him, and the oppressive force from her presence made even a Guardian like him feel a twinge of fear.

”You think you can offend the Commander and still walk away?”

”Did I say you could leave?”

Tohru asked, enunciating each word.

...

The Great Tomb of Nazarick.

Throne Room.

A vast hall filled with piles of gold stacked like mountains.

The Sorcerer King held his staff and struck it to the ground.

”Revive, Cocytus!”

Fwoosh—

A wave of energy spread from his staff.

After crossing into this world, the Sorcerer King—Suzuki Satoru—retained a portion of his YGGDRASIL powers.

For example, reviving allies by consuming resources.

Reviving a Level 100 Guardian without level loss required spending billions in gold. Fortunately, Ainz Ooal Gown’s guild was still quite wealthy.

The mountain of gold gradually melted into a golden energy liquid.

It took shape on the floor, solidifying.

Eventually, it became Cocytus’ original form.

After a moment of disorientation, the insect king immediately bowed his head in apology.

”Lord Ainz, it was my incompetence in battle that brought you shame.”

”You even spent resources to revive me… this is…”

”Stand up, Cocytus. I don’t blame you.”

The Sorcerer King sat back on his throne.

”I merely intended to use you to test the enemy’s strength. They… are indeed very powerful.”

Ainz’s skeletal fingers tapped restlessly on the throne’s armrest.

He had been overthinking this whole time out of fear that this world might harbor an incredible being.

And now the nightmare had come true.

It turned out to be a bunch of people piloting starships who treated super-tier magic like basic attacks—completely different rules of engagement.

And they were from the technology side.

”Lord Ainz, what about the other Guardians?”

Cocytus looked around.

The usually lively throne room was empty.

Chatterbox Shalltear and Aura were absent. Strategist Demiurge was gone too.

Only Albedo remained at Ainz’s side, acting as his assistant.

”I sent them to launch a teleportation raid on the enemy Commander.”

Ainz replied.

Out of caution, he hadn’t used magic projection to monitor the assault team’s movements.

Demiurge was one of his most trusted Guardians, adept at adapting on the fly.

With Shalltear’s peerless combat power, and Aura and Mare bringing the Depiction of Nature and Society—

taking one ship should have been a trivial task.

It was a calculated gamble to turn the tide.

”Lord Ainz, with Shalltear and Demiurge’s abilities, they will surely succeed and bring back the enemy Commander’s head.”

Seeing Ainz agitated, Albedo tried to comfort him.

”...”

”Let’s hope so. But in the meantime, we must prepare for the worst—fortify Nazarick’s defenses and activate all traps.”

”Also, create another batch of undead. Prioritize the defense of Floors 1 through 3.”

Ainz pondered for a moment.

The Guardians had only been teleported aboard recently. Given the ship’s size, taking some time was understandable.

Still, if the enemy planned a full-scale assault on Nazarick, he had to be ready.

”From what we’ve seen, they seem completely immune to low-level magic. Regular spells can’t harm them...”

Ainz rested his chin on one hand, deep in thought.

Though Cocytus was instantly killed, he still gathered some intel—like how starships had shields and resisted conventional attacks.

”Immune to low-level attacks. That means... only rule-manipulating abilities can stand a chance?”

As the Overlord of Death, he had some instant-kill skills based on system mechanics.

”Grasp Heart? No, their levels are surely high. That skill would only stun them.”

”Falling Sky? Not strong enough—less powerful than starship weapons. Cut? Death is the end of all life?…”

Ainz pondered a while and really wished he had the Spear of Holy Annihilation.

A legendary item said to delete a target from the game entirely—one of the most unreasonable among the ”Twenty.”

Sadly, Ainz Ooal Gown didn’t have it.

”Forget it. I’ll go find Pandora’s Actor—I need to borrow a World-class item.”

Just as he was about to rise—

Beep—

A prompt sounded.

The YGGDRASIL interface opened before him.

In the Guardian roster, Demiurge, Aura, Mare, and Shalltear all had red crosses next to their names.

The Pleiades too.

”!!!”

”Ah?!?”

Ainz froze.

Scrape—scrape—scrape!!!

He Triggered his forced calm down several times before he sat back down.

What the heck?

The four Guardians he just sent out, the Pleiades, and dozens of Soul Eaters—all annihilated?!

”Impossible?!”

Ainz wondered if he had misclicked the coordinates and dumped them into a volcano or something.

—Given their strength, even dropping them anywhere on the planet shouldn’t kill them this fast.

”Lord Ainz, this...?”

Even Albedo was visibly shaken.

Four Guardians and the Pleiades perished almost simultaneously—an extremely rare event in Nazarick’s history.

Fear.

Ainz felt a pure and overwhelming fear.

He couldn’t comprehend what had happened or how the enemy did it.

This was no longer theoretical strategy against an invisible opponent, pretending the enemy might be strong.

The enemy was strong—incomprehensibly strong!

Those starships were sitting right in front of them and could one-shot a Level 100 Cocytus.

Even under surprise attack, the ship’s crew wiped out four Guardians and the Pleiades in short order—without even sending a single message back.

The starship crew were all stronger than Level 100 Guardians?!

That was terrifying.

If your crew were this powerful, why even bother flying the ship?!

Ainz screamed in his mind.

Where’s the logic in this?!

Fine, your tech weapons killed Cocytus in one hit—I’ll concede that your engineering is myth-tier.

But silently taking down that many Guardians—what the hell?!

It’s like a warrior finally closes the gap on a mage for a melee, only to have the mage toss aside their staff and beat the fully armed warrior barehanded.

Where’s the Depiction of Nature and Society? Mare? Do something!!!

”Damn.”

Ainz shut down mentally.

He felt this game’s balance was deeply flawed.

After all his time being a heavy-spending whale, he’d finally run into a hacker from another world.

After the battle ended, aboard the Eternal Snowfall, the maids and Angeloids began cleaning up the battlefield.

Fortunately, the starship’s structure was sturdy enough. Even with shipgirls using small-caliber supergravity cannons inside, and Heroic Spirits casually tossing around Noble Phantasms, there was no real damage.

Only a few wall sections had changed color, and the floor was littered with sticky, wet goo.

Soul Eaters exploded into foul-smelling liquid upon defeat.

Tohru, unable to bear it, used magic to clean everything up repeatedly.

”Commander, you’re really something.”

Gudako praised sincerely.

”I expected the Eternal Snowfall’s outer defenses to be tough, but you’re just as solid on the inside?”

”Artoria, Jeanne Alter, and Nero must’ve thrown at least seven or eight Noble Phantasms just now, plus attacks from the Royal Maids—and you didn’t feel a thing?”

She leaned close to inspect the wall. Aside from the marks Belfast left when executing the Pleiades, there wasn’t even a scratch.

”Of course. You can try it yourself sometime. Shipgirls all say it’s great.”

Setsuna rubbed Gudako’s head and made a casual joke.

”Commander?!”

Mio nudged him with her elbow, blushing.

”Ahem—”

”Seriously though, the ship’s hull is an extension of my body—inside and out, it’s all the same.”

”I can even activate the Klein Field internally. Pretty amazing, right? So boarding actions are meaningless.”

Setsuna explained.

Shipgirls or ships born from the Allspark didn’t have traditional ”weak points.” Trying to sabotage them from the inside wasn’t any easier than blasting them from the outside.

Even if someone managed to board the ship, they’d still face a shipgirl—in essence, a full-fledged starship.

Not to mention, there was a very simple countermeasure to boarding:

—Just retract the ship. Anyone inside would get ejected immediately.

”Tch, definitely broken.”

Gudako clicked her tongue, feeling that Setsuna was even stronger than she’d imagined.

Not long after—

Belfast walked over with a large sack.

”Commander, while cleaning up the battlefield, we found some loot. Please have a look.”

Clatter—

The head maid dumped out a pile of strange items onto the control console.

Most of it came from Demiurge, Shalltear, and the others—equipment left behind after they were defeated.

There were scrolls, potions, and oddly shaped trinkets.

Setsuna and the others casually picked up a few but weren’t interested.

Summoning demons, fireballs, lightning storms, ice spikes—none of that was needed.

They’d been to more than one sword-and-magic world, and these things were all functionally similar.

The only thing that caught Setsuna’s attention was the scroll Aura had pulled out earlier—

the World-class item: Depiction of Nature and Society.

Because Nero broke it with her Noble Phantasm, ownership had transferred over.

Setsuna spread it out on the table and opened it.

Fwoosh—

The scene before them changed instantly, entering an alternate-dimensional space much like before.

”Oh?!”

The dragon girls, shipgirls, and Heroic Spirits all looked around, surprised.

”World-class items have greater rule manipulation than regular skills.”

Setsuna rubbed his chin thoughtfully.

World-class items were balance-breaking artifacts in the game, each with unique effects or rule-bending properties—a level above ordinary skills.

They were the most valuable items in the Overlord universe.

Would their rule-level control still work outside this world?

Setsuna was very curious.

He stored the Depiction of Nature and Society away.

”Let’s study it back home. It’s quite an interesting artifact.”

Its effect was similar to a Reality Marble—pulling enemies into a separate dimension.

However, the Depiction of Nature and Society had plenty of options. From the anime, it could generate sealed spaces, thunderstorm weather, deserts, and other extreme conditions.

It also had features like enemy duplication and spawning mobs out of thin air in the dimensional space.

Aura even kept her magical beasts stored inside it.

Its downside was obvious—if an opponent escaped from the alternate space, the item’s ownership would transfer.

”Commander, do we need to search for other World-class items? If we deploy the Angeloids for a full-grid sweep, efficiency would be high.”

Belfast asked.

”No need.”

Setsuna shook his head.

”This is a world conquest. Once we win, everything will be ours.”

”At the very least, I expect to receive one of each World-class item, right? Ideally, a blueprint too—if those even exist.”

As long as this world was conquered, all lost or vanished artifacts would be treated as spoils and distributed.

While discussing, Richelieu sent a transmission:

”Commander, I heard some noise from the flagship earlier. Did something happen?”

”Ah, it’s fine. The Sorcerer King sent some people to attempt a boarding raid. Already handled.”

Belfast replied casually.

”Eh eh eh?!”

Richelieu was shocked.

The next moment, Taihou jumped through a porthole and wrapped Setsuna in a passionate hug.

”Commander-sama!!!!”

”Are you hurt?!”

Other shipgirls hovering nearby also jumped over, crowding around Setsuna with questions.

”Were the enemies strong? Did they cause any damage? How did they even get here?”

”...”

The Royal Maid shrugged.

”No idea. They yelled something about friendship, bonds, and Supreme Beings, then charged in.”

”Then we blasted them into the floor.”

”...”

”Please have more faith in your Commander, thank you.”

Setsuna cleared his throat, motioning for everyone to return to their stations.

”Now that the farce is over, let’s get to the real task.”

The unexpected boarding assault had thrown Setsuna slightly off rhythm.

He hadn’t expected World-class items to be used like that.

Still, before the overwhelming firepower of a space fleet and conventional superiority, this was just the Sorcerer King’s desperate resistance.

Aside from offering four Guardians and the Pleiades as warm-up practice—and dropping some loot—it accomplished nothing.

”Search target: locate the Great Tomb of Nazarick.”

With one command—

The Eternal Snowfall’s sensors activated at full power.

Hundreds of carrier aircraft launched from the hangar, dispersing in all directions.

On the holographic radar interface, scans of the surface streamed in.

The Sorcerer King had hidden Nazarick’s presence using World-class items and various spells.

Without a meticulous grid search, it would be hard to pinpoint its location.

That wasn’t a problem for Setsuna. He’d read the lore and roughly knew where the Tomb was.

Located near the center of this world’s continent, bordering several human nations: Re-Estize Kingdom, Slane Theocracy, Baharuth Empire.

Once the general area was determined, scans became more precise.

Whoosh—whoosh—

Waves of carrier aircraft skimmed low.

Many adventurers and villagers looked up in awe, staring at the starships and planes overhead.

Primitive minds couldn’t comprehend such advanced technology. They assumed it was divine intervention or some epic spellcasting.

Soon, the onboard AI reported:

”42.3 km northwest, underground region shows abnormal high-energy readings.”

”Sensor interference detected—unable to complete full holographic modeling of subterranean space.”

A large red dot appeared on the map.

”This is it.”

Setsuna snorted.

The starship fired its thrusters and quickly arrived at the marked location.

Below was a barren wasteland. Nothing seemed unusual to the naked eye.

But sensors indicated otherwise—as if a massive underground space was concealed there.

Boom—

Several Angeloids descended.

After breaching the ground, they exposed a layer of purple barrier.

”Oh, a defensive ward?”

Gudako peeked over.

”Commander, can Mio and Tohru break this? Ainz is hiding underneath, right?”

”Shall we go find him ourselves?”

She looked eager to pilot Barbatos and go duel the Sorcerer King.

”What, go dungeon-crawling through Nazarick?”

Setsuna was amused.

”Start from Floor 1, solve puzzles, avoid traps, defeat each Floor Guardian, then reach the Throne Room to challenge the Sorcerer King?”

”What are we—adventurers?”

”Ahf?”

Gudako blinked, confused:

”We’re not? The Sorcerer King’s probably hiding on the tenth floor or even deeper, right?”

”I don’t like such dumb procedures. Makes me and my ship look stupid.”

Setsuna locked the main cannon onto the target and began charging.

”Wouldn’t it be simpler to just blow the lid off Nazarick?!”

”I don’t believe it can withstand a planet-destroying cannon.”

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