Crossover Shipgirls: Building a Dimensional Empire from Scratch

To demonstrate Chaldea’s sincerity, Romani brought Setsuna to a room resembling an engineering department.

A young woman in a red and blue dress, with long black hair, greeted them.

”Hello, I am Leonardo da Vinci, Chaldea’s technical advisor. I’ve heard about your situation from Doctor Romani,” she said. ”You’re looking for some magic materials from our world, correct?”

Da Vinci greeted the group warmly.

Before Setsuna could respond, one of the shipgirls behind him tilted her head with a puzzled expression.

”Da Vinci?! How is Da Vinci a cute girl?!”

Looking at the graceful young woman with long black hair and green eyes, they couldn’t reconcile her image with the legendary artist and inventor they knew.

”Welcome to the Nasuverse. It’s a magical place,” Setsuna said with a smirk. ”Here’s another secret for you: King Arthur is also a cute girl. So is Nero, and they even look alike.”

He ignored the shipgirls’ stunned expressions and addressed Da Vinci directly.

”I need a comprehensive magic system—oh, and the summoning arrays for Heroic Spirits as well.”

Da Vinci considered his request, then handed him several worn tomes.

”We have some scattered magic documents here. The rest will take time to organize and gather. Once you’ve resolved the Singularities, I’ll ensure everything is delivered to you.”

”As for Heroic Spirit summoning,” she continued, ”it’s relatively straightforward. What we summon are not the Heroic Spirits’ true forms but their Servant projections. You simply need to draw the summoning array, recite the incantation, and follow the prescribed steps.”

”However, summoning hinges on the relics. You must possess an item associated with the Heroic Spirit in life. Additionally, the Heroic Spirit must willingly respond to your call.”

Setsuna scanned the provided materials. The summoning array itself didn’t seem complicated—straightforward enough to replicate.

As for relics, Chaldea didn’t have many to spare, but Setsuna believed he could find substitutes in other worlds.

”Servants require their Master’s mana supply to sustain themselves. Without magic circuits, it’ll be difficult for summoned Heroic Spirits to remain stable…” Mash warned, her tone kind.

”No problem,” Setsuna replied confidently. ”I have a magic cube. Let’s hope the Heroic Spirits can integrate with it. If not, I’m open to ’mana transfer’ techniques.”

”M-Mana transfer? What’s that?” Ritsuka Fujimaru asked, her eyes widening in confusion.

...

After acquiring the magic texts and summoning instructions as a ”down payment,” Setsuna began preparations to assist Chaldea.

The group descended to a smaller chamber, where a glowing blue globe was suspended mid-air within a forcefield.

”This is the ’Chaldeas Simulated Global Environment Model,’ one of Chaldea’s most critical devices,” Romani explained.

”With this device, we can observe Earth’s future and use it as a map of human history.”

Romani gestured toward several points of light on the globe.

”The recent Incineration of Humanity has created seven Singularities. Each one represents a critical juncture for human survival. Currently, we’ve managed to pinpoint the first Singularity, which seems to be located in 1431 France.”

Romani briefed the group, detailing the situation.

”After entering this world, recovering the Greater Grail and correcting the historical anomalies, this Singularity should return to normal.”

”The Dragon Witch War, huh? I’m quite familiar with it,” Setsuna said with a knowing smile.

”Jeanne Alter and Jeanne d’Arc? I’ll try to bring them both back.”

”How are we going to get there?” Formidable asked curiously.

”Spiritron transfer,” Romani explained, leading everyone to a massive machine.

”This is the Spiritron Calculation Engine. It can convert Masters into a spiritron form, projecting them into different eras.”

”This technology is extremely dangerous. It could even be used as a time machine, which is why every use requires UN approval.”

”Of course, now that humanity has been wiped out, we don’t need anyone’s permission.”

”...”

”That’s incredible… I heard that the Sirens were researching parallel world technology, but I’ve never seen anything like this in person,” Richelieu remarked, deeply impressed.

Crossing through time was a pinnacle achievement in any world.

”So… if there are no further questions, prepare yourselves. I’ll project you to the Singularity,” Romani said, preparing to count the participants.

”Wait!!!”

”Can I get a copy of this machine’s blueprint? I can trade resources for it—gold, silver, or anything else you need,” Setsuna interrupted, his gaze fixed on the Spiritron Transfer Engine.

”Huh? Normally that wouldn’t be allowed, but since you’re from another world, I suppose it doesn’t matter…” Romani hesitated briefly before nodding. ”After we resolve this situation, I’ll try to get you a copy.”

”Do you plan to use it to rewrite history?”

”No, no, nothing like that—for now,” Setsuna answered with a wave of his hand.

”It’s just that with this, I can accomplish a lot of things.”

”?”

Seeing their confusion, Setsuna elaborated.

”When ordinary people use Spiritron Transfer to travel into the past, they can only return through the device, and they can’t bring back anything from that era.”

”But I’m different. I have the authority to open space-time portals, which means once I’m sent to an era, I can open my own portal to return.”

”This capability doesn’t just cover regrets but also solves some particularly troublesome problems.”

”For instance, that Spirit of Origin hanging on the mission list for ages.”

...

”Now then, let me go over the mission objectives one last time.”

After Setsuna’s intense interest in the Spiritron Calculation Engine caused some delays, Dr. Romani addressed the gathered group once more.

”You will be traveling to the first Singularity, which is set in France during the year 1431.”

”There are two main objectives. First, investigate and correct the Singularity. This means identifying the decisive historical turning point for humanity during that era.”

”You need to determine exactly what occurred and take the necessary steps to fix it.”

Setsuna nodded, signaling he had no questions. As a veteran Master, he already knew the issues plaguing the first Singularity. With his knowledge, he could go straight to the target, skipping much of the preliminary investigation.

”Second, you must investigate the Holy Grail. During your investigation of the Singularity, you will undoubtedly uncover information related to the Grail.”

”Even if you successfully correct the timeline, leaving the Grail behind would render all efforts futile.”

”Thus, the Holy Grail must either be destroyed or recovered.”

”Understood.”

Ritsuka looked somewhat uncertain, but the sight of Setsuna and the shipgirls accompanying him gave her a small boost of confidence.

Having more companions when venturing into an unknown world was always reassuring.

”The entire group is going? The Spiritron Calculation Engine can only send seven people. Any more, and there won’t be enough power,” Romani explained as he glanced at Setsuna’s entourage.

There was Richelieu, Taihou, Formidable, and another girl with golden hair, blue eyes, and an elegant rapier at her hip. Together with Ritsuka and Mash, they made seven.

”Hello, I am Jeanne d’Arc, the light cruiser from Iris Libre, Triomphant-class.”

Jeanne introduced herself gracefully.

”???”

Romani and Ritsuka only understood the first half of the introduction and were utterly baffled by the second.

”Jeanne d’Arc?! What?!”

”You have a Jeanne, and I have a Jeanne. Let’s not get caught up in the details.”

Setsuna smirked. Bringing Richelieu and Jeanne—two French ships—on a mission set in France felt like a natural choice.

”...”

”Alright, fine,” Romani relented, giving up on unraveling the mysteries he couldn’t comprehend.

”Once you’re transferred to that era, your first task is to locate the ley lines and establish a summoning circle.”

”This will allow you to summon additional Servants freely. However, any summoned Servants will most likely be tied to the era and location you’re in.”

”Understood?”

He spoke like a father fussing over his children.

”Understood,” Mash replied with a firm nod.

”Very well then… initiating Spiritron Transfer!”

”Good luck out there—may you all return safely!”

The group of seven stepped into the Spiritron Calculation Engine.

[Reverse Summoning System: Activated]

[Beginning Spiritron Conversion]

[Time Until Spiritron Transfer Begins…]

”5”

”4”

”3”

”2,” ”1”...

[Process Complete!]

[First Singularity: Orléans]

Boom—

Swish—

Accompanied by the mechanical broadcast, the scene before them abruptly contracted into a black void.

The bodies of Setsuna’s group instantly became semi-transparent, existing in an ambiguous state between life and death.

Then, it was as if no time had passed—or perhaps an eternity had gone by.

Setsuna opened his eyes again.

”Ugh, a bit dizzy. This is worse than the commander’s space-time tunnel,” one of the shipgirls muttered, shaking her head to clear her senses.

The seven of them took a moment to observe their surroundings.

A bright blue sky and scattered clouds stretched above a vast expanse of grasslands and rolling hills. In the distance, smoke curled gently from the chimneys of a medieval-style village.

They had arrived in 1431 France.

”This should be during the Hundred Years’ War between England and France,” Mash assessed as she scanned their surroundings. ”But it seems the fighting hasn’t reached here yet. The area feels relatively peaceful.”

”Does anyone speak French or know the local customs?” Mash asked.

”Leave it to me,” Richelieu responded with a soft laugh.

As the flagship of Iris Libre, a pure-blood French noble, a cardinal, and the embodiment of old Parisian traditions, there was no one better suited to the task than her.

”First, let’s find a leyline and summon some Servants,” Setsuna instructed as he cleared his throat.

”Understood,” Ritsuka and Mash replied, unconsciously falling in line with his commands. There was an air of natural leadership about him that was difficult to resist.

The area where they had been transferred was desolate, almost devoid of people. Even sightings of common soldiers were rare.

As they walked, Setsuna explained the situation regarding this Singularity to the group.

In the original timeline, during the Hundred Years’ War, Joan of Arc, the Saint of France, had been condemned by the Inquisition and burned at the stake in 1431.

However, in this Singularity, due to some mysterious power, Jeanne had been resurrected three days after her execution. Returning to the world as a blackened, vengeful Servant, she sought to destroy France and summoned seven powerful allies with the Holy Grail to aid her cause.

Resolving the Singularity required dealing with both Black Jeanne and the Holy Grail.

As for the comparative strength of the two sides...

The enemy team consisted of Black Jeanne and her seven Servants. On their side, there were four shipgirls, plus Ritsuka and Mash.

A large-scale battle seemed inevitable.

But Setsuna was confident. In the original storyline, Ritsuka and Mash managed to resolve the conflict by themselves. With their current team, victory seemed assured.

”No matter how you look at it, the Battle of Orléans will be four shipgirls versus eight Servants. The advantage is clearly mine!”

...