Crossover Shipgirls: Building a Dimensional Empire from Scratch

"It can project a person into any world, to any point in its historical timeline?"

The gathered shipgirls, there to watch the spectacle, were utterly stunned.

Chaldea's Spiritron Calculation Engine could only be used to alter the history of its own world, like eliminating the seven Singularities to restore proper Human Order.

Using Chaldea's device to project someone into another world was, of course, impossible.

However, the hybrid Spiritron Calculation Engine before them could do just that.

"It's not as fantastical as it sounds," Purifier scratched her head thoughtfully.

"After all, we don't have the Commander's kind of power to see the multiverse as a map and identify different universes at will."

"To be precise, this is just a mainframe used to perform Spiritron calculations."

"The prerequisite for using it is that you first travel to the target world and build a receiver there. That way, the mainframe can locate the world."

"Then we activate the device to Spiritronize you and project you onto that world's historical timeline."

She pointed to a nearby tower-shaped apparatus.

"That's still pretty absurd!" Richelieu exclaimed in admiration as she gazed at the enormous structure.

By simply adding the step of constructing a receiver, it essentially allowed unrestricted time travel across worlds.

"What are the usage limits and participant numbers?" Setsuna asked.

He recalled that Chaldea's device could only transfer seven people at a time.

"There's no limit on the number of participants, but cross-world traversal consumes a tremendous amount of energy... and each world's stability differs," Compiler replied indifferently.

"For now, the maximum range is about 30 to 60 years of temporal traversal. Each activation, depending on the number of people, will require at least 100 cubes…"

"?!"

"This thing eats cubes?!"

Setsuna was stunned. This was the first time he had heard of cubes being used as consumables.

"Cross-world Spiritron transfers require an enormous amount of energy as payment, Commander," Akashi's ears twitched as she explained.

"The most energy-dense resource we currently possess is the Wisdom Cube. If we used a nuclear reactor, it probably wouldn't even power up the Spiritron Transfer Device."

"Fair enough."

After some thought, Setsuna conceded. Even hundreds of cubes were affordable.

Still, this gave him a new perspective on its power.

Wisdom Cubes were Azur Lane's pinnacle black technology, containing unfathomable amounts of energy. For this machine to consume hundreds of them per use was staggering.

Cross-world temporal traversal indeed came with a steep price.

Fortunately, the base had plenty of Bulins, and resources from three worlds were available.

"But only 30 to 60 years? I recall that in Chaldea, you traveled from modern times to Rome, crossing over 2,000 years in one go," Nero tilted her head and asked.

"That's because it was calculating for its own world. If activated in the same world, sending you back 20,000 years wouldn't be difficult," Purifier answered while crossing her arms.

"Of course, if you build a mainframe in someone else's world, you could achieve a similar effect, but it's a lot of trouble."

"Are you interested in traveling to this world's past?" Purifier suddenly leaned in, gazing up at Setsuna and asking earnestly.

"…"

Setsuna thought about it for a moment.

"Forget it."

When he arrived, this world's humanity had already been extinct for thirty years, conveniently within the Spiritron Calculation Engine's temporal range.

However, projecting into the past meant even the smallest actions could cause butterfly effects, altering the future's course.

He felt everything was good as it was now.

The base's development was on track, and he was surrounded by shipgirls, Heroic Spirits, and dragon girls.

There was no need to change anything. Focusing on the future was more important.

...

Back at the administrative center, Setsuna immediately opened the Hyperdimensional Star Map and began examining it.

Though limited to traversing timelines of 30 to 60 years, there were still plenty of possibilities.

Whoosh—

A projection of dazzling stars appeared before him.

He scanned the nearby worlds.

"Goblin Slayer… hmm, could go back and find a pristine Sword Maiden? That sounds interesting, though the gods over there are a bit troublesome…"

"As for the Type-Moon world… after dealing with the Singularities, heading to Fuyuki to take out Zouken Matou and save Sakura would be straightforward. Not much trouble there…"

Suddenly, his gaze landed on a world mission that had been hanging in the Date A Live world for a while.

[World Mission: Date A Live]

Mission Objectives:

 • Resolve the threat of the Spirit of Origin and eliminate the Spirits' influence on the human world.

Mission Rewards:

 • Spirit Sealing Technique.

"…"

This anime was something Setsuna was very familiar with.

It was basically the story of an ordinary high school student legally building a harem by sealing the powers of Spirits.

He had seen plenty of fan works featuring Kurumi before, including many full-color ones like "Kurumi X Refrain" which were part of his collection.

After thinking for a moment, he realized there were two ways to tackle this mission.

One was to bring a large force over, eliminate the Spirits and the Spirit of Origin entirely, and bring lasting peace to the world.

The other was to figure out how to win over the Spirit of Origin.

All the Spirits had originated from the Spirit of Origin.

If he could conquer her, he could solve the problem at its source and potentially take the rest of the Spirits with him.

Setsuna figured building a team composed entirely of Spirits would be a nice addition—time to expand the species compendium.

He had postponed this mission previously because the Date A Live timeline was notoriously complex, and the Spirit of Origin was absurdly powerful in the early stages.

It wasn't impossible to end up defeated as soon as he landed.

But now, he could intercept events earlier.

He turned his attention to the mission reward:

[Spirit Sealing Technique:]

You can seal the spiritual power of Spirits.

With mastery, you can temporarily borrow the abilities and Angels of the Spirits around you.

"???"

This sounded suspiciously like Shido Itsuka's signature skill, minus the conditions of needing to kiss and make the other party blush.

As for borrowing a Spirit's Angel…

Their combat strength varied, but some of their abilities in time and rule manipulation were incredibly powerful.

Soon, he called together a few shipgirls and Tohru, the dragon maid.

"We're heading to another world to bring back a Spirit."

"???"

Everyone froze in confusion.

"You mean those fair-skinned, slim-limbed, pointy-eared, blonde, scantily-clad creatures who are always being kidnapped by orcs and goblins?"

Tohru wagged her tail as she spoke.

"What kind of ridiculous stereotype is that?!"

Setsuna exclaimed, stunned.

"That's how Elves are in our world," Tohru said, shrugging. Next to her, Kanna nodded in agreement. (Note: "精灵" is technically the same word for both Elves and Spirits.) 

"Uh, no. Spirits in Date A Live are created from Spirit Crystals and look no different from humans," he explained.

"The one we're looking for is the Spirit of Origin. Solve her, and everything else is resolved."

Setsuna then gave everyone a brief introduction to the plot and the situation.

The shipgirls and Heroic Spirits all exchanged peculiar glances.

"So, the mission in this world is to help the Commander… romance the Spirit of Origin?"

"Why does this feel so strange?!"

Once again, Taihou's expression morphed into her trademark yandere face.

"As expected, pests from other worlds… it's better if they disappear, isn't it? Hehehehe…"

"Calm down!"

Setsuna began to reason patiently, appealing to logic.

"If we don't resolve the issue with the Spirit of Origin, she will be entangled with various organizations in the future, and whenever other Spirits manifest, they will bring disasters to that world."

"Taking her away in advance can save many lives…"

He then explained several disasters caused by the Spirits.

"…"

Taihou's attitude softened immediately.

"So… you're doing this to save humanity in that world?"

"Well, sort of? This way, the Date A Live world stabilizes, allowing for sustainable—no, let's not get into that now."

Setsuna nodded.

"Then, Commander, you mustn't neglect me afterward…"

Taihou snuggled into his arms, pouting like a spoiled child.

Setsuna patted her head, coaxing her with a few kind words, and soon, her face broke into a smile.

"As long as it's for you, Taihou will help with anything you need."

Richelieu and Yat Sen thought it over. They were more curious about the identity of the Spirit of Origin.

After hearing her backstory, they realized that Date A Live was essentially Mio Takamiya's tragic tale.

Helping her didn't seem like a bad idea at all.

"…"

Jeanne Alter and Gudako, however, were dumbfounded.

"Master, how do you make going to another world to build a harem sound like such a righteous act of saving the world?!"

"Ahem—"

Setsuna cleared his throat and stood up.

"This is saving the world."

"Target: Date A Live World. Mission: Go on dates with Spirits!!"

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