Crossover Shipgirls: Building a Dimensional Empire from Scratch

No matter what.

Under the Siren girl’s combination of threats and temptations, the Autobots and Decepticons finally achieved a true, world-level reconciliation.

Cybertron was rebuilt in a short time through the authority of the Herrscher of Reason.

Clang clang clang—

Bumblebee looked around and knocked on his own head a few times, suspecting that his visual module had malfunctioned.

Out of curiosity, Wheeljack and several Decepticons went to inspect the factories.

Everything constructed through the Herrscher of Reason’s authority was absolutely precise—perfectly accurate.

It flawlessly replicated the blueprints previously given to Setsuna.

As for the missing sections, he had supplemented them according to his own understanding, using the Starsea Empire’s technology.

Even now, every Transformer on Cybertron felt as if they were sleepwalking, unable to comprehend what had just happened.

”I... uh...”

”Thank you.”

At a loss for words, Optimus Prime bent slightly at the waist and saluted Setsuna.

If Setsuna had merely transported supplies from the Starsea Empire to support Cybertron, the Autobots could at least have contributed something.

They would have been mentally prepared.

But refurbishing the entire planet in a matter of minutes—it was so outrageous they wouldn’t dare dream of it.

Optimus Prime hadn’t even finished thinking of a proper speech of thanks before Setsuna had already completed the task.

”...”

After the Autobots and Decepticons barely reconciled, all the Transformers fell into silence in the face of this miracle.

They looked at one another. Some were questioning their existence. Others simply had no idea how to react.

A miracle.

For mechanical lifeforms, the concept of ”god” was not easy to grasp.

Yet Setsuna stood before them like one.

Clap—

It wasn’t until Bumblebee clapped loudly that everyone snapped back to their senses.

”Celebrate!!”

”The Starsea Empire helped us rebuild Cybertron—and they’re our friends!”

”Since they’ve come to visit us, we have to celebrate!!!”

...

Later that evening.

Cybertron’s North Pole, Iacon.

This was the administrative center of the entire planet. Magnificent metallic structures could be seen everywhere.

Inside a massive steel-forged palace.

Setsuna sat at the head seat. His position had been elevated considerably by the Transformers—like a throne raised by more than ten meters—so that he appeared at roughly the same height as them.

Beside him were the accompanying shipgirls and the other girls.

The Transformers sat in a circle around the hall, each holding energon cubes and chugging them down in celebration.

Ever since Cybertron’s decline, they had not replenished their energy so freely in a very long time.

Those few dark matter reactors were enough to supply all Transformers. As long as no chaos erupted, their future energy reserves would be virtually endless.

”Cheers, brothers!!—”

”To our friends from another world!!—”

Bumblebee raised a large cup of liquid fuel in a toast.

During his time living on Earth, he had learned quite a bit about human etiquette.

Setsuna raised a smaller glass and clinked it toward him from afar with a smile.

Formidable and Illustrious, seated beside him, looked especially curious. They had attended many banquets before, but dining with Transformers was a first.

The Transformers had insisted on treating the great benefactors who saved Cybertron to a meal.

It was just that the ”food” they prepared made the little shipgirls twitch their lips.

”Wow, aren’t these snacks brought from Earth? The packaging isn’t even opened?!”

Little Formidable leaned over and picked up a few bags to inspect.

They were probably taken from some supermarket on Earth—chips, spicy gluten sticks, pickled chicken feet and the like. Fine as snacks, but rather odd as a formal banquet spread.

Thump—

Formidable gently knocked her on the head.

”It’s the thought that counts. Don’t nitpick.”

”Honestly, I’d rather try drinking energon with them...”

Several little shipgirls muttered among themselves.

Hoo—

”So, may I ask what happened after you returned to the Starsea Empire?”

”And how did you use the Allspark and the Transwarp Key?”

Optimus Prime asked curiously.

He had willingly handed those two items to Setsuna before—first because of the Starsea Empire’s overwhelming strength, and second because they genuinely owed him a favor.

But seeing him again now, Optimus Prime had the distinct feeling that Setsuna had used them in ways far beyond his understanding.

”The Allspark is now part of me—and part of the Eternal Snowfall.”

Setsuna smiled and unfolded a portion of his ship rigging.

Within the main control module, the dark metallic cube was fixed upon a pedestal, continuously supplying power to both the starship and himself.

The Transformers were even more astonished.

A human capable of merging with the Allspark—it was something they had never encountered before.

”With the power of the Allspark... no wonder.”

Megatron leaned forward slightly, his gaze deep and shocked.

”Hoh...”

The two sides exchanged stories for a while.

Then Optimus Prime suddenly remembered something important.

”You said there’s one more thing to do in this universe?!”

”Yes.”

Setsuna nodded.

Sending the Autobots home and saving Cybertron were promises he had made earlier.

The remaining matter was the unfinished business of this world.

”We intend to crusade against Unicron.”

”!!!”

All the Transformers froze for a moment.

Joking about it in a holographic interface was one thing.

Hearing Setsuna formally declare it was another.

”Unicron is a threat to us.”

The nanorobot took over the explanation.

”Think about it. That thing floats around in a dead dimension all day, constantly looking for opportunities to descend into the physical universe and devour a few planets to replenish its energy.”

”If we don’t eliminate it, how can we safely develop this universe? What if one day it eats Earth or one of our colonies?!”

Grey might not particularly care about the lives of Earthlings—the nanorobot discriminated equally against everyone except Setsuna.

But those worlds were still Imperial territory. The Transformers universe had plenty left to explore and develop. It would be a shame to let it be destroyed.

”Mm...”

The Autobots fell into contemplation.

”Unicron... is indeed dangerous. Even if its true body cannot descend into this universe, it can dispatch its Scourge Legion to carry out its will.”

”Wherever they pass, there is only war and destruction. The homeworld of Scourge was destroyed by that calamity. It is a terrifying opponent.”

The Decepticons wore strange expressions.

In the past, they had some connection to Unicron. Their ideologies were quite similar.

If Setsuna had not intervened, in a few more years it would have been almost certain that Megatron would pledge himself under Unicron’s banner.

But now, standing before the unfathomable Starsea Empire that had rebuilt Cybertron—

The Decepticons were pondering something else entirely.

Was Unicron strong enough?

Between Unicron and the Starsea Empire... which one was stronger?

The Decepticons pursued power. Even with a truce declared, that trait would never change.

”Unicron represents the embodiment of destruction and chaos. Unlike us, it is a god. It cannot be defeated.”

Megatron said solemnly.

”Our Commander is a god too. We have hundreds of them on our side.”

Grey said dismissively.

”From Outer Gods of Cthulhu mythos to Heaven’s goddesses and all sorts of strange deities from various legends—what’s the big deal? Haven’t they all been disciplined into obedience with a stick by the Commander?”

”???”

Megatron felt as if they were talking about two completely different concepts of ”god.” He couldn’t understand a word.

Thud—

Setsuna knocked her lightly on the head.

He flipped through several pages of data on the holographic interface and spoke calmly.

”Unicron’s origin is indeed that of a conceptual god transcending time and dimensions—an embodiment of destruction and chaos.”

”However, within the physical universe, it can only descend in a material form. As far as I know, it has expended a great deal of power within that dead dimension. The strength it can project here is limited.”

When he first arrived in the Transformers universe, Setsuna had already confirmed that this was the timeline of Transformers 7.

At this time, Unicron was still lingering in a universe known as the Dead Universe, seeking ways to descend into the primary universe and devour planets to replenish its energy.

Its combat form resembled a planet-sized warship.

It had been difficult to handle before.

Now, there were plenty of methods available.

”Oh...”

Optimus Prime did not fully understand, but seeing Setsuna so confident, he could only ask further.

”Then how do you intend to deal with it?”

”We’ll use the Transwarp Key to open a passage to that dead dimension. Then we’ll lure that idiot out and beat it up.”

Grey said confidently.

”After that, we’ll see if there are any useful parts or treasures we can install into the Eternal Snowfall.”

”By the way, the name ’Unicron’ sounds pretty domineering. Commander, why don’t you change your name to Starsea Emperor instead?”

”Bro, why do I feel like this is a terrible idea?!”

The next day, on Cybertron, the Transformers stared blankly as Setsuna laid out the battle plan.

Bumblebee had upgraded his form of address from ”buddy” to ”bro”—because in his opinion, this plan was absolutely outrageous.

A considerable number of fleets had been mobilized. Carrier shipgirls and battleship shipgirls formed battle formations in space, their expressions faintly excited.

Nyaruko and several Cthulhu girls accompanied them as well. It wasn’t just technological force—if anything unexpected occurred, the Ancient Gods would also step in.

”Relax, relax. We’ve run the simulations many times. There won’t be a problem.”

Grey reassured the alarmed Transformers while assigning each detachment fleet its role on the holographic map.

”In a moment, Commander will use the Transwarp Key to open a passage to the Dead Universe.”

”At that time, Unicron will inevitably follow the channel and descend into this physical universe. We must take it down in one go.”

”After confirming the destruction of Unicron’s main body or disabling its propulsion system, the engineering division will move in with me. Priority objective is to seize control of the hull. If that fails, we’ll drag it back for research.”

The nanorobot raised her arm decisively. Shipgirls, research lolis, and expedition members all nodded.

”Understood!”

Excitement appeared on many little shipgirls’ faces. An interstellar war—against the ultimate boss of another world—just thinking about it was thrilling.

Akashi, leading the engineering division, rubbed her hands eagerly.

”Got it, nya~”

Every technological creation from another world had to be carefully dismantled and studied.

”...”

Optimus Prime realized that Setsuna clearly hadn’t been discussing how to deal with Unicron yesterday.

He had already made his decision before arriving.

”Bro, if there’s anything we can help with, just say it.”

Seeing that the Starsea Empire was determined to see this through, Bumblebee flew over to ask.

When it came to challenging a villain like Unicron, the Autobots wouldn’t back down.

”Uh...”

Setsuna thought for a moment.

”You can stay on Cybertron, grab some popcorn—well, energon cubes—and treat it like a show?”

”Hey?!”

Bumblebee performed a 360-degree aerial maneuver, flexing his steel arm as if showing off his strength.

”We’ve been upgraded too, you know? At the very least, fighting in the air isn’t a problem!”

Optimus Prime was also preparing to rally the Autobots to assist, but Setsuna declined with a smile.

”We were the ones who upgraded you in the first place. Mm... it’s still a bit early for you to challenge Unicron.”

”Focus on protecting yourselves and Cybertron.”

”???”

The Transformers returned to Cybertron in frustration, sitting in neat rows.

They felt deeply regretful about not being able to help.

However, they would soon understand that a war of this magnitude was not something the current Transformers could participate in.

”...”

”First Fleet in position.”

”Second Carrier Fleet in position.”

”Subspace traps deployed. Standing by...”

As reports came in one after another.

On the bridge of the Eternal Snowfall.

Setsuna took out the Transwarp Key—the strange metallic object shaped like a spearhead when assembled.

After faster-than-light technology and jump engines had been developed, its research value had been exhausted. It had become little more than a collectible.

In the Transformers universe, however, it could still serve another purpose.

Bzzz—

He drew upon the power of the Allspark and infused it into the Transwarp Key.

The Allspark represented creation-level energy within the Transformers universe—sufficient to tear open a passage to another universe.

The two energies resonated. The Transwarp Key emitted a humming vibration, trembling as it floated in the air.

Then.

When the internal energy gathered to a certain threshold.

Whoosh—

The Transwarp Key transformed into a dazzling blue beam in the starry sky, shooting toward the other end of the universe, millions of light-years away.

A rift was torn open in the fabric of the material universe.

...

Within the boundless darkness.

No starlight. No planets.

Only endless void and blackness filled the cosmos.

No energy could be obtained here. No interaction with space itself was possible. Even the concept of time seemed blurred.

To be cast here meant only one fate—exhaust your energy in infinite emptiness and ultimately fade into annihilation.

This was a land of exile.

A universe of death.

A planet forged of machinery drifted slowly within the void.

Its entire body was composed of black metal, its surface covered in intricate mechanical patterns. Along its equator stretched a colossal structure resembling a mechanical maw running from north to south.

The maw emitted a blinding glow, as if seeking to devour everything in existence.

”Hungry...”

Unicron was starving.

The Scourge sent to retrieve the Transwarp Key had failed. Even the Terrorcons had vanished without a trace.

Its original plan to feast upon Earth had fallen through.

It could only remain within this endless Dead Universe.

”...”

Rumble...

Within the void, only the faint resonance of its massive body echoed intermittently.

For an existence like this, time held little meaning. Hundreds or thousands of years were merely numbers.

It wandered aimlessly, accumulating strength, intending to assemble another Transformers legion under its command.

To enter the physical universe.

To seize the Transwarp Key.

To escape this universe.

No one knew how long had passed.

Shff—

A dazzling beam suddenly pierced through space.

In an instant, Unicron recognized it.

The Transwarp Key.

A passage to the material universe had opened.

It hesitated for only a fraction of a moment.

The Scourge Legion had clearly gone silent. The mission had failed. So who had activated the Transwarp Key this time?

Yet under its overwhelming hunger for matter—

The planet-sized warship immediately followed the pull of the Transwarp Key, descending from the Dead Universe.

BOOM!!!—

From the torn rift in the starry sky.

Unicron’s colossal hull slowly emerged.

A mechanical planet descended from the void.

It gazed down upon the scene below—the physical universe it longed for beyond measure.

There was a sun. There were planets. Countless civilizations and life.

Wonderful.

All of it would be its food and nourishment.

Near a triple-star system, several metallic planets orbited.

Cybertron.

Unicron was familiar with it as well—the homeworld of the Transformers.

Though the scenery upon its surface had changed somewhat.

Fortunate timing.

While it was not Earth, Cybertron was not far from the solar system.

It could devour this place first.

Then proceed to Earth for a proper feast.

”Heh heh heh heh heh...”

”This planet... is mine...”

Terrifying pressure descended.

At the forefront of the planet-sized warship, the monstrous mechanical maw opened, as if ready to swallow the entire world whole.

”?”

In the next moment, Unicron noticed something discordant in the distance.

A colossal warship faced it across the void.

Though slightly smaller than itself, it too had reached planetary scale—yet its structure was entirely different.

On either side of the main hull, massive armed wings stretched like those of an eagle, spanning thousands of kilometers and loaded with innumerable weapon systems.

The axial main cannon beneath had already completed its charge, emitting a deep crimson glow.

Behind it, an entire space fleet stood in orderly formation—battleships, carriers, cruisers...

”?”

”Who are you?”

Unicron’s voice carried deep authority as it questioned the fleet before it.

”...”

The other side remained silent for two seconds.

Then the reply came—accompanied by countless high-energy weapons firing simultaneously:

BOOM!!—

”Target has descended! Lock on!”

”Full fire coverage!!!”

—

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