Crossover Shipgirls: Building a Dimensional Empire from Scratch

”Eh? Who are you?!”

After returning from the Life Sciences Division, Griseo caused quite a stir in the administrative center.

Fu Hua stared blankly at the grown Griseo.

Strange. Some people couldn’t grow even after fifty thousand years, while others underwent a single procedure and, in just a few hours, went from a little loli to a 36D beautiful girl.

”What are you staring at, old fossil? You’ve lived for tens of thousands of years. Even if you switch to a juvenile form, it won’t help, you know?”

Senti, as usual, started running her mouth at the Immortal.

”Don’t tell me you used to be big and then shrank as you grew older? Stop staring. This technology won’t work on you.”

”???”

Fu Hua’s frosty expression twitched. Her hand moved to rest on the Xuanyuan Sword as she considered whether to give Senti a lesson.

”Ah, the grown Griseo is beautiful too~”

Cecilia, as always radiating maternal warmth, helped smooth Griseo’s hair and tidy her clothes.

”You should be able to get along well with Kiana. Oh, do you want to attend classes at St. Freya?”

”Griseo has already finished all the materials she needed to study. She came earlier than you. Don’t really treat her like a child.”

Setsuna said with a smile.

Little Griseo’s nature had always been more like clarity of heart and pure simplicity, completely different from childish immaturity.

”Eh, but if that’s the case, does that mean Kiana could turn back into little Kiana too...?”

Cecilia suddenly found herself missing the little white-haired dumpling from before.

Cute and adorable, speaking in a sweet, coquettish tone, and not yet trying to compete with her own mother for the Commander’s affection.

”...Kiana only wants to grow up now. She’d be one hundred percent unwilling to turn back.”

Setsuna laughed.

”Why don’t you try it instead...?”

”Eh? Me? My childhood self?”

Cecilia was startled.

”Th-That wouldn’t be appropriate, would it?!...”

”Commander, please do not use the greatness of biological science as a tool to spice up your personal life.”

Ritsuka Fujimaru voiced strong protest.

After the brief commotion, Setsuna looked at the grown Griseo.

”So, is there anything you want to do?”

”Mm...”

Griseo thought for a moment.

”I want to experience the lives of the other big sisters. Walk around the capital... and other places too.”

Ever since arriving in the capital, she had spent most of her time quietly sitting before her canvas, painting.

The colors of the Starsea Empire could never be fully captured. Now that she had suddenly grown up, Griseo found herself wanting to go out and explore.

It felt as if her mind had matured along with her body.

”That’s fine. You’re a MANTIS. Your strength shouldn’t be an issue.”

Setsuna agreed casually, then thought of something.

”But if you’re going out to fight... you’ll need a weapon, right?”

Buzz—

He extended his hand, Honkai energy condensing within it.

Using the authority of the Herrscher of Reason, he shaped a metallic object resembling a sword hilt.

Its blue-black casing was adorned with intricate star patterns, trimmed with dark-gold accents along the edges. It looked both magnificent and futuristic.

”Here. A gift for you.”

Griseo took it. The craftsmanship was exquisite. It felt heavy in her hand and reacted faintly with Honkai energy.

She infused a small stream of Honkai energy into it.

At once, a long, pale-blue beam blade extended from the hilt, much like the lightsabers wielded by Jedi in Star Wars.

At the same time, complex transformation mechanisms activated, allowing it to shift into a massive cross-shaped mechanical construct.

”Eh? What is this?”

The grown Griseo looked puzzled.

”It’s the Anchor of the Voyage · Interstellar PLUS edition. Your exclusive weapon. It boosts the entire team’s bleed damage... ahem, no, that’s not it.”

Setsuna cleared his throat.

”It’s a weapon I forged for you using Honkai energy. It’s no weaker than a Divine Key. Make good use of it.”

In theory, giving Griseo a space battleship and making her a starship pilot would be the fastest way to boost her combat power.

But watching a beautiful girl wield a lightsaber had its own kind of romance.

”Oh... thank you.”

Griseo only half understood. She could sense that this weapon was far more complex than it appeared. The authority of the Herrscher of Reason had constructed an incredibly intricate internal structure.

She nodded and casually swung it a few times.

Her movements were somewhat loose, imitating techniques she had seen in movies before.

Fortunately, with Honkai energy and her physical prowess, brute force was more than enough.

”If you want to learn swordsmanship, there are many people in the capital who can teach you.”

Setsuna smiled.

”Magic and other combat techniques using Honkai energy too. Cecilia, Fu Hua, Kallen, Himeko—they can all teach you.”

”Then can the Commander teach me?”

Griseo asked softly.

”I want... to get used to this kind of life.”

”Uh... if I have time, sure.”

...

The grown Griseo became one of the regular figures by Setsuna’s side.

She began experiencing a new life as an ”adult.”

During the day, she helped out in the administrative center, taking responsibility for various design projects across the Starsea Empire.

”Griseo, please! We’re counting on you for next semester’s art textbooks!!!”

”And don’t forget my illustrations!!!”

”Can I commission a piece? Maybe paint a portrait for me?...”

Thanks to her unique aesthetic perception and painting skills, every department that needed artwork competed to recruit Griseo.

In her free time, she learned combat techniques from Setsuna or others.

Bang—smack—

In the training ground,

Setsuna casually formed a weapon out of Honkai energy and exchanged blows with Griseo.

Whoosh—

The beam blade swept through the air in dazzling arcs. Its destructive power was equally astonishing. With Honkai energy enhancement, each strike carried enough force to split mountains.

Boom—boom!—

Griseo darted and pivoted, leaving behind faint blue afterimages in her wake...

In an instant, she closed the distance to Setsuna.

With dazzling technique, she launched a barrage of attacks, the blue beam blade weaving a dense net of sword light.

Setsuna neither dodged nor retreated. He stood firmly in place, one hand behind his back.

Clap!

With two or three casual movements, he effortlessly dissolved her attacks into nothingness.

Swish—

Before Griseo could react, the tip of Setsuna’s blade was already poised before her.

He had not used any power beyond her comprehension. This was purely a contest of technique.

The purpose was instruction, not flaunting superiority or crushing his opponent.

”Your movements are a bit too flashy. If the goal is to kill the enemy, they need to be streamlined.”

”Mm... but from another perspective, your moves are very beautiful,” Setsuna added.

”You’re improving quickly. Before long, you’ll be able to spar properly with Cecilia and Kallen.”

Griseo had very little real combat experience. When she had followed him on expeditions to other worlds before, it had mostly been for gathering inspiration. She would usually remain on the ship, quietly painting.

To reach a level close to an S-rank Valkyrie in such a short time could only be described as exceptional talent.

”Mm... thank you, Commander.”

Griseo picked up the beam blade that had been knocked from her grasp and gave Setsuna a small bow.

Training was exhausting.

She sparred with Setsuna, with Cecilia, with Kallen, and even practiced against Gudako, Goddess Rhongomyniad, and Origami Tobiichi.

She had to think of every possible way to deal with her companions’ strange and varied techniques—Heroic Spirit Noble Phantasms, Gundams, Spirit magic...

It was far more tiring than sitting in a chair painting all day.

But it was interesting.

She could feel herself growing stronger day by day, learning to see the world from a different perspective.

Not as a child kept under protection, but as a member of a combat squad.

The colors of the world shifted in an instant, forming countless new inspirations in Griseo’s mind.

”...”

Bang—smack—

One day,

After yet another training session.

Setsuna handed the beam blade back to Griseo and pinched her cheek lightly. An Angeloid promptly stepped forward and offered them two bottles of drinks.

”Not bad. Aside from close-quarters combat, you should also learn some long-range methods.”

”Magic or Honkai energy—it’s up to you. Once the database scanning is complete, you can also use False Epigraphy.”

He was very satisfied with Griseo’s training results.

”If there’s an opportunity, you can start accompanying the combat personnel on missions.”

”Mm...”

Griseo looked at herself, then at the weapon in her hand, momentarily lost in thought.

”I can... go with them too...?”

She recalled how, in the Previous Era, she had always been protected by her seniors.

Mother Aponia, Sister Elysia...

Fragments of memory surfaced in her mind.

Suddenly, Griseo remembered something.

...

”Commander, can you take me with you... to save them? I want to go back and see Mother Aponia...”

After the routine training session ended, Griseo gently tugged at Setsuna’s clothes and looked up as she made her request.

”Oh?”

Setsuna paused.

”My companions... they’re all people from the past.”

”Commander, you once said we could return to the past and change it, right?”

After spending some time in the Starsea Empire,

Griseo had met many of the companions Setsuna had brought back from the Honkai world.

Kallen, Cecilia, Theresa... and the Valkyries from St. Freya Academy.

Unfortunately, the only person from her own era was Fu Hua.

The people she had once known, the ones who had taken care of her, had all vanished into history along with the fall of the Previous Era.

”If... I go back now, could I help them?”

”What would Mother Aponia and Sister Elysia think if they saw me like this now?...”

A flood of questions spilled from Griseo.

She wanted those companions to see who she had become.

”Mm...”

Setsuna thought for a moment.

”Strictly speaking, whether you participate in battle during the Previous Era doesn’t really matter. The Herrscher of Finality wasn’t something their era could defeat.”

”Then...”

Griseo tugged at his sleeve again, her eyes filled with hope.

”But I’ll take you there. So it’s fine.”

...

Two hours later.

In the administrative center, Setsuna projected the hyperdimensional star map and selected the Honkai world.

”Come to think of it, after returning from the Current Era last time, there was still a loose end.”

”We’ll settle it during the downtime before the next expedition.”

Previously, the hyperdimensional starship had traversed several hundred years within the Current Era. After merging with the Cocoon of Finality, Setsuna had decided to first fully familiarize himself with the Herrscher authorities before heading to the Previous Era.

After clearing No Game No Life, the Sixth Singularity, Transformers, and adding daily training along with the power of the Suniaster, he had now largely mastered and grown accustomed to the power of Finality.

”Oh...”

Cecilia, Theresa, and the others from the Current Era gathered around, flipping through materials about the Previous Era.

To them, Kallen was a historical figure from hundreds of years ago. The Thirteen Flame-Chasers of the Previous Era were myths from tens of thousands of years past.

Without the data provided by the Starsea Empire, most people of the Current Era would never even realize the Previous Era had existed.

”So... these were our predecessors in the fight against Honkai?”

Cecilia leaned her head against Setsuna’s shoulder.

”Each era gives birth to Herrschers one by one, meant to end human civilization. They ultimately failed the trial of the Herrscher of Finality.”

”But if not for the legacy left behind by the Previous Era, humanity might have been destroyed by the Herrschers all over again, right?...”

”Of course. The technological level of the Previous Era was higher than that of the Current Era.”

Setsuna pinched her cheek lightly as he spoke.

For a considerable period, the Current Era had developed its technology largely through archaeology.

”Hah?!”

Tesla, who had been working nearby, looked up in protest.

”No way. I don’t believe that.”

”The knowledge you previously learned about Honkai energy was discovered aboard Griseo’s Ark. The Starsea Empire only refined and corrected parts of it.”

”The data stored on the Ark was preserved by the Previous Era to rebuild civilization. It contains all the scientific achievements and cutting-edge theories of that time.”

”Can you honestly say you’ve fully understood all of it?”

The nanorobot twirled a pen in her hand.

”Eh...”

Tesla obediently fell silent.

She had to admit that without the Starsea Empire’s assistance, she was still some distance away from the scientists of the Previous Era.

”...”

After reviewing the general situation of the Previous Era,

Everyone came to the same conclusion.

Tragic. Too tragic.

With no prior experience and starting from scratch against Honkai, everything had been unknown.

Each new Herrscher—the Herrscher of Corruption, the Herrscher of Binding, even the Herrscher of Flames—had inflicted devastating casualties through sheer surprise.

Even so, they had managed to leave behind hope for future generations to defeat Honkai.

”Mm... those predecessors were truly remarkable.”

”The Starsea Empire’s Honkai technology originated from the legacy of the Previous Era. And now we’re using their technology—from the future—to go back and save the past?”

Einstein leaned back in her chair, gazing at the holographic dome.

”When you think about it... it’s rather romantic, isn’t it?”

It reminded her of a certain science fiction film, where future humanity reached across time to help those in the present.

”The Commander just wants to rescue more girls...”

Before Gudako could finish her sentence—

Bonk!

She took a direct hit to the head and crouched down, clutching it while glaring at Setsuna.

”Why did you hit me?!”

”Because you told the truth out loud.”

Setsuna cleared his throat.

”Fifty thousand years. Using the spiritron transfer system before would have been troublesome. But with the hyperdimensional starship, it just means spending more time traveling through higher dimensions.”

”And now that I’ve fused with the Suniaster and the Cocoon of Finality, resolving the problems of the Previous Era will be easy.”

”Mm...”

Einstein stared at Setsuna and Griseo for a long moment.

”Commander, I’ve discovered a bug.”

”You fused with the Cocoon of Finality. You are the future Herrscher of Finality. But logically speaking, the Cocoon of Finality in the Honkai world has always been a single entity from beginning to end.”

”If we travel back again, what will happen?...”

”Also, with authority over Finality, the other Herrschers are theoretically split from your power. When the time comes... the situation might become very strange.”

Einstein rubbed her temples. Her already messy hair looked even more chaotic.

Technically, traveling back to solve Honkai wasn’t difficult.

But the more one thought about it, the more minor issues appeared.

”And the people of the past? Fu Hua and Griseo are both from the Previous Era, right? What happens if they meet themselves?...”

”Temporal paradox? We might need to revise relativity again.”

”...We ran into this kind of problem long ago in the Date A Live world.”

Setsuna tapped the table lightly.

”As long as we’re careful not to create a temporal bug, it’ll be fine.”

”As for the Cocoon of Finality... I have absolute control over Honkai energy. When the Herrschers of the Previous Era see me, they should be the ones kneeling.”

The Cocoon of Finality was the sole imaginary singularity and Herrscher core, controlling everything related to Honkai at the edge of the Imaginary Tree. All Herrschers were connected to it in some hidden manner.

They were merely shadows of Finality—projections upon the real plane.

Now that the Eternal Snowfall had merged with the Cocoon of Finality, for other Herrschers to face Setsuna was akin to facing Finality itself.

”...You’re going to scare the locals.”

Tesla clicked her tongue.

Soon, Setsuna began assembling the team that would travel to the Previous Era.

Planck, Tesla, Einstein, and the other scientists naturally signed up eagerly, hoping to conduct research and exchange knowledge with scholars of the Previous Era.

The girls from the Honkai world also expressed their desire to see fifty thousand years in the past.

A few days later.

Flash—

The Eternal Snowfall departed from the capital, passed through a transmission anchor point, and after a burst of blinding light, descended upon the Honkai world.

—

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