Crossover Shipgirls: Building a Dimensional Empire from Scratch

”So, you’re a teacher at the Starsea Empire’s Imperial Valkyrie Academy, and your Astral Express isn’t Akivili’s tool, but purely a technological creation?”

After their initial meeting, the two Himekos immediately began an in-depth exchange.

”Mm... it’s the Second Divine Key, manufactured and modified by Vill-V.”

Murata Himeko studied her other self with a hint of surprise.

”You repaired your Astral Express yourself?”

”Yes.”

The girl opposite her nodded.

”It had run aground on my home planet back then. I spent many years repairing it, then piloted it into the stars to Trailblaze more new worlds.”

”We met March 7th while the train was traveling. She was sealed inside a drifting block of Sx-Phased Ice at the time, so she boarded along the way.”

”How wonderful...”

Murata Himeko could not help but sigh.

Her former dream had been to become a scientist. In university, she had majored in interstellar navigation dynamics.

After entering St. Freya, she had worked for a time as a Valkyrie instructor. Then, in the Starsea Empire, she once again had the opportunity to step into the sea of stars and explore the universe.

And now she had met another version of herself who embodied that ideal. She could not help but marvel at how miraculous fate could be.

The two of them had completely different backgrounds and life experiences.

Yet they possessed identical appearances, identical names, and even strikingly similar ideals and personalities.

By sheer coincidence, they had each piloted an Astral Express and met here.

It was practically a bond that transcended time, space, and even the universe itself.

Glug glug—

Murata Himeko pulled out a bottle of red wine and poured two glasses.

”To you, to me, and to ourselves.”

”I usually drink coffee, but red wine works too.”

The two clinked glasses.

”But I still don’t understand. Why are there two completely identical Instructor Himekos?”

Raiden Mei looked left and right, still visibly conflicted.

”It’s not that big a deal. When the Commander explored the Tree and Sea before, didn’t he bring back a girl named Astrologos from another world bubble?”

Kiana recalled for a moment.

”Astrologos looks exactly like Aunt Theresa too, right? Mm, it’s probably just ourselves from parallel worlds or other world bubbles.”

”The Commander also said that in this universe, encountering counterparts isn’t anything strange. Look, over at Chaldea, aren’t there Jeanne Alter, Jeanne d’Arc, the King of Knights, the Lion King, Saber Alter, Lancer Alter, and all sorts of variations...”

”That makes sense.”

Thinking about the two Theresas in the capital, along with that whole pile of Artorias, everyone felt that running into counterparts did seem reasonable.

”?”

Himeko and March 7th had no idea who Jeanne Alter or the King of Knights were, and were thoroughly baffled by the odd explanation.

But since the other side had provided a theory that at least sounded logical, they accepted it for the time being.

”Another me from another universe... interesting.”

The two Himekos clinked glasses again.

”Tell me about your side of things?”

Talking to oneself always came unusually easily.

They began with childhood experiences, moved on to their student years and choosing their majors in university, and then to the different paths they had taken in their respective worlds...

And finally, they had met again because of the Starsea Empire’s expedition.

The two were engrossed, one sipping coffee and the other red wine, chatting from afternoon all the way until deep into the night.

They felt as though they had met too late.

That was the only feeling shared between Himeko and Himeko.

They had the same dreams and the same beliefs, yet each possessed a different story.

The Astral Express’ Himeko listened to Murata Himeko recount her experiences at St. Freya and her encounter with the Starsea Empire, as if she were personally reliving her life.

Murata Himeko deeply admired the way the other Himeko could freely explore among the stars. She had achieved the dream Murata Himeko once held as a child.

When conversing with oneself, there were no barriers at all. They were even slightly curious—if they were to switch identities, what would they become?

The next morning.

Kiana, still bleary-eyed, knocked on Himeko’s door.

”Instructor Himeko, today we need to—whoa!!”

A wave of alcohol fumes hit her face.

Both of them were drunk, likely having talked through the entire night.

The Astral Express’ Himeko had an arm slung around Murata Himeko’s shoulders, speaking with a slurred tongue about all sorts of strange things.

”H-hey... tell me more? Have you dated anyone over there...”

”No!! There was so much going on at St. Freya, how would I have time?”

”Hic!—I mean now! Do you have a partner?!”

”Are you some marriage-urging auntie?!”

Himeko clung to Murata Himeko, determined to dig out some gossip.

”No!! There are too many people in the Starsea Empire! When would I even get the chance?!”

”Silly! If you can’t find an opportunity, create one... tsk tsk... wait, no, someday let me see what your Commander actually looks like...”

”What the heck???”

Kiana was stunned.

”Instructor Himeko, it’s only been one night! Your relationship has already progressed to gossiping about private matters?!”

”Hic—”

Murata Himeko let out a drunken hiccup and beckoned to her.

”What gossip? We’re clearly the same person.”

”Come, Kiana. Let me introduce you. This is my newly acknowledged little sister—my dear younger sister from another world, with different parents.”

”?”

The Astral Express’ Himeko, equally flushed from drink, slammed her wine glass onto the table.

”Don’t take advantage of me! I’m the older sister! Call me big sister!!”

”You’re the younger one. I’m the senior.”

”Not convinced? Let’s spar a bit. Whoever’s stronger is the older sister!”

”Bring it on! Whoever loses changes her name!!”

The two grabbed their coats and staggered toward the door with utterly incomprehensible drunken steps, determined to settle who ranked higher.

”???”

The white-haired girl felt her worldview crack on the spot.

...

One hour later.

”Ahem—”

After sobering up, the two Himekos summoned their respective train crews.

”So, that’s the situation. Both the Astral Express and the Starsea Empire’s advance team will be staying at Herta Space Station for a period of time.”

”Mm... we can use this chance to learn more about each other. If there’s time, I’d like to visit the Starsea Empire.”

Himeko said.

After one night of conversation, she and her other self had reached a consensus and become cross-world sisters.

She had also developed a strong curiosity about the place Murata Himeko lived in—a world even the Aeon of Trailblaze had never set foot in.

”No problem! The Commander will definitely welcome you!”

Kiana thumped her chest in assurance.

”Mm... then please rest at the space station for now. I’ll arrange accommodations for everyone.”

Asta clapped her hands.

”Perfect. I also want to get in touch with the Starsea Empire... mm.”

After much thought, she had finally decided to take that step and see a more distant starry sky within the Starsea Empire.

”Oh right, Miss Asta and Madam Herta have both decided to join the Starsea Empire. So does that mean Herta Space Station is practically merging into the Starsea Empire too?”

Kiana scratched her head.

”Don’t worry, don’t worry. This young lady will protect you all!!”

”Mm... but I’ve heard Madam Herta has lots of interesting collectibles here. Could you take me to see them?”

”Ah?”

Asta’s expression turned slightly awkward.

”The Nameless Domain is Madam Herta’s private collection vault. Only she has the authority to enter... mm, perhaps you could ask her?”

”Is there something in particular you want to see?”

”Of course—the one-of-a-kind greatest treasure of this space station!!”

...

At the far edge of the distant stars.

A small spacecraft was warping toward Herta Space Station.

Inside the main control cabin, a woman dressed in a white fitted top, black shorts, and black tights sat leisurely, listening to classical music.

Her long purple hair was tied in a ponytail. A pair of sunglasses rested on her forehead. Her mature features carried a trace of seductive charm.

Keeping time with the music, she lightly waved her hand in steady rhythm, as though intoxicated, conducting a grand symphony across empty space.

Buzz—

The piece came to an end.

Kafka opened her eyes and gazed at the azure planet slowly rotating in the distance.

”We’re almost there,” she said softly.

”This mission is very simple. Just as Elio’s script describes, we only need to place the target inside.”

”Understood.”

Beside her, a holographic interface unfolded, transmitting the calm and indifferent voice of another girl.

”In 27 hours, 14 minutes, and 26 seconds, the space station’s main control system will be struck by a pulse shock, causing widespread paralysis. We will act in sync at that time.”

”There’s space at the station’s platform. You can land there.”

”Mm.”

Kafka nodded lightly.

Knowing what would happen in the future was equivalent to obtaining the script in advance—to seeing fate.

Acting became extremely simple.

”But I have a small question.”

Silver Wolf paused briefly.

”Did Elio mention why there are two Astral Expresses here?”

”If it’s not written in the script, then it isn’t important.”

”...Are you sure?”

”Mm.”

...

After staying at Herta Space Station for two days, the two train crews gradually grew familiar with one another, and even became acquainted with Asta.

”Miss Asta, I want to see Madam Herta’s collectibles~”

”She already agreed!”

Kiana spent all day eyeing Herta’s collection of curios.

Originally, Herta’s collection was something of an urban legend within the space station. The vast majority of researchers had never even laid eyes on it.

Fortunately, Herta herself was currently immersed in the Starsea Empire’s new technologies. After instructing them to pay attention to safety, she casually granted permission.

”Uh... originally, only Madam Herta herself had access to the Nameless Domain. Since she has given you authorization, then... please follow me.”

After passing through a complex identity verification system, Asta led the group deep into the station’s storage area.

All sorts of strange and unusual devices were sealed within display cabinets.

”This is the prototype Astro Rod, invented by space station researcher Hosea Lazaro. It’s a tool used to survey extraterrestrial geological structures.”

”No matter how hard a planet’s geological structure may be, simply insert the drill lightly into the surface, and it can extract a large amount of geological material without effort...”

They carefully examined each item one by one. Herta’s collected curios might not all possess overwhelming power, but many were extremely interesting.

”This is Joy Filtration Set—a set of twenty-one small portable devices, each separately sealed within cubes of unique material.”

”Different devices can identify and collect joy and joy-like emotions.”

”And this is the Rating Pistol. Aim it at an object, and it will automatically assign the target a score. The principle behind it is unknown.”

”Ooh!”

Kiana was instantly drawn to the device, which looked somewhat like a forehead thermometer gun.

An eye was embedded in the gun’s body, half-lidded. When held, it rolled around mischievously, giving off a somewhat lecherous vibe.

Click!—

She aimed it at a bouquet of flowers. 2 points.

Then she pointed it at herself.

Beep—

Unable to determine! After the eyeball spun in circles three times, it suddenly widened, held for a moment, then closed wearily.

”What the heck? Is it because I’m an alien?”

The white-haired girl puffed out her cheeks and immediately aimed the Rating Pistol at Bronya, Raiden Mei, and Himeko.

”No. It’s too ugly. Bronya refuses to be rated by it. Bronya gives it zero points.”

”Instructor Himeko, do you think your score will be higher, or the other Sister Himeko’s?”

”Does that even matter...?”

The group quickly devolved into playful chaos, having the time of their lives.

Suddenly—

Wooo—

A thunderous alarm echoed throughout the interior of the space station.

[Alert. Emergency response mode activated.]

[Alert. External signal intrusion detected.]

Boom!—

Outside the station, hundreds of collapse points abruptly appeared, and bizarrely shaped warships poured out from within.

”That is...?”

A researcher beneath the transparent dome looked up.

Within space itself, countless black teleportation points lit up one after another.

Boom!—

Imaginary power tore open black rifts in space.

Countless monsters clad in dark armor quantum-leaped directly from the outside into the interior of the space station.

Blue-violet flames burned across their bodies. They wielded all manner of strange weapons. Even meeting their gaze for a single instant brought a suffocating sense of evil and destruction.

”The Antimatter Legion!!!”

A researcher was the first to scream.

They were the vast army commanded by the Aeon of Destruction, Nanook. Their purpose was singular—to bring chaos and devastation to countless worlds.

Every appearance and assault of the Antimatter Legion spelled disaster for civilized worlds.

At the same time, in the station’s Master Control Zone, data warnings blared wildly.

[Alert! Alert!! The Base Zone is under attack.]

[Research sector breached! Entrances sealed!]

An overwhelming number of Antimatter Legion forces launched a full-scale invasion of Herta Space Station.

Using quantum leaps to jump directly into the station’s interior, they began frantically attacking every lifeform they encountered.

”Guide the evacuation! Move quickly!!!”

Asta was the first to react.

Within the Master Control Zone, she hurriedly directed the staff to take shelter.

”The station’s anti-gravity defense net won’t hold for long. Head to the safe zone!!!”

”Miss Kiana, Miss Himeko, everyone—I’m very sorry, please evacuate with me.”

Out of her duty as station chief, she called out to Kiana and the others.

They were guests from the Starsea Empire. She could not allow anything to happen to them.

”Evacuate?”

The white-haired girl blinked, tossed aside the toy in her hand, and cracked her knuckles.

”No, that’s not right.”

”Prepare for battle!!!”

”Mm.”

Raiden Mei drew her weapon. Bronya, Seele, and the other train crew members readied themselves as well.

”The Antimatter Legion is very dangerous!! There are too many of them!!! Hundreds... no, thousands of invaders are attacking the station!”

Asta cried out.

Before her words had even fallen—

Zzz—

A dark sphere of light ignited within the hall of the Master Control Zone.

Black light flickered as dozens of Voidranger Reavers broke through the station’s outer defenses and invaded the interior.

Clack!—

Encased in black-purple armor, their arm guards extended into two several-meter-long mantis-like blades.

Though Voidranger Reavers were only basic combat units, once their numbers increased and they were directed by higher-ranking Voidrangers, they could still cause considerable trouble.

”Move!!!”

At the very moment the Voidrangers launched their charge—

Rumble!!!—

A violent surge of Honkai energy swept through the entire Master Control Zone.

Murata Himeko drew a blazing crimson greatsword, shattering the Voidrangers and shielding everyone behind her.

”Kiana, weren’t you complaining that classes at the academy were too boring every day?”

”This is your first surprise live-combat assessment. Perform well.”

”Understood!”

Kiana, Bronya, Raiden Mei, and the others were brimming with excitement.

They did not yet possess the capability to participate in large-scale interstellar warfare, but this kind of small-scale encounter was perfect.

Just the right opportunity to test what they had learned at the Imperial Valkyrie Academy.

Slash—

Mei wielded her blade, weaving gracefully through the Voidrangers, effortlessly cutting down the puppets brimming with destructive power one by one.

Bronya activated her Honkai energy. A half-body metallic mecha manifested behind her.

”Project Bunny, deploy!”

The mecha held a shield in one hand and a lance in the other, imposing and majestic.

Bang!—

It moved in sync with her, launching close-range assaults.

Like slicing vegetables, a casual thrust skewered an entire row of Voidrangers like candied hawthorn on a stick.

Zzzrt!—

Gamma-like energy weapons were mounted on its shoulders. High-energy beams streaked through the air, cleaving charging enemies in half at the waist.

”W-what is that?!”

March 7th, who was still shooting arrows nearby, stared in shock.

She felt as though she and Bronya were not even from the same era.

”Mm. This is the weapon the academy equipped for Bronya. I call it Project Bunny,” Bronya replied expressionlessly.

”It is a technological creation combining Ex-Machina manifestation devices, Gundam technology, and Honkai energy.”

”Bronya cannot pilot a Gundam, so she usually uses it for combat instead.”

Since Seele and Bronya had been taken in by the Starsea Empire very early on, there was naturally no incident of Seele becoming quantum.

To facilitate Bronya’s combat capabilities, they had crafted something similar for her—its performance even surpassed the original version by a significant margin.

”Hoh...”

”You truly are full of surprises.”

The other Himeko watched the Starsea Empire’s train crew mowing down Voidrangers like weeds, her interest piqued.

They wielded a power system completely different from this world’s—utterly unlike anyone she had encountered before.

”Come then. A rare opportunity. Let us see each other’s strength, shall we?”

Himeko joined the battle alongside March 7th.

”But... there are too many Antimatter Legion forces! Mm...”

Asta anxiously watched the surveillance screens at the main control console.

The two train crews had blocked the fiercest wave of Voidrangers, giving her enough time to evacuate the researchers.

Yet the Antimatter Legion’s assault continued endlessly, leaping into every corner of the station. Alarm sirens rose and fell in constant succession.

”Why would they suddenly attack here?... Could someone have deliberately guided them to the space station? Mm...”

”Mm, we must find a way to activate the internal defensive weapon systems and drive them out...”

Herta Space Station had rarely been attacked. Even when assaults occurred in the past, Herta and the Interastral Peace Corporation had been able to resolve them.

But this time, the scale of the Antimatter Legion’s invasion was far larger—wave after wave like a raging tide, alarms blaring throughout the entire station.

”It’s fine.”

Kiana molded various weapons out of Honkai energy while responding.

”Isn’t it just calling for backup? We can do that too!!”

”Miss Asta, you and Madam Herta have both joined the Starsea Empire. So... this place is Starsea Empire territory!!!”