Crossover Shipgirls: Building a Dimensional Empire from Scratch

The Demon Slayer Corps was desperate to learn how to create an artificial sun to destroy demons.

Unfortunately, understanding nuclear fusion was as difficult for them as researching the Trisolaran droplet technology would be for humans.

Despite Setsuna explaining the concept as simply as possible, the Corps members were left with blank, incomprehensible expressions.

Kanae and Shinobu couldn't stop scratching their heads.

Their heads itched, as if trying to grow new brains.

Fortunately, they grasped one simple truth:

It didn't matter if the Demon Slayer Corps could defeat Muzan. What mattered was that Setsuna and the shipgirls could.

Their responsibility was to locate Muzan and the Twelve Kizuki. Once found, the rest would be handled by these otherworldly "heavenly soldiers."

After all, Richelieu had obliterated Douma, Upper Rank Two, with ease, demonstrating that no Upper Rank demon could withstand her firepower.

"So, the real question now is, how do we find the remaining Twelve Kizuki and Muzan?"

Everyone fell into deep thought.

Muzan Kibutsuji, the boss of the Demon Slayer world, had survived for over a thousand years not just because of his brutality and strength, but primarily because of his caution—or rather, his cowardice.

He remained hidden in the shadows, commanding his demons from safety.

At the slightest hint of danger, he would disappear without a trace.

During the Sengoku era, after being nearly killed by Yoriichi Tsugikuni, he went into hiding and only reemerged after confirming Yoriichi's death.

Setsuna suspected that upon learning of Douma's defeat, Muzan might revert to his old tricks and vanish entirely.

If he burrowed into some remote mountain cave, it might take years to find him, which Setsuna didn't have the patience for.

"Perhaps we could send out more Demon Slayer Corps members to hunt for him?" Kanae suggested.

"If anyone spots Muzan or the Twelve Kizuki, we could immediately call for Mr. Setsuna's support."

"That would be difficult," Kagaya Ubuyashiki, the Corps' leader, shook his head.

"Ordinary Corps members wouldn't even have time to react before being killed by an Upper Rank demon, let alone call for reinforcements."

"Then how about using ship-based aircraft to support the Demon Slayers? We could strike the demons from the air—surely they can't withstand bombs," Illustrious proposed.

With three aircraft carriers in their group, they had hundreds of reconnaissance planes and bombers capable of covering vast areas.

The Demon Slayers could track the demons on the ground while the aircraft conducted airstrikes upon discovery.

"Did you pick this up from Essex? But it won't work either," Setsuna shook his head.

"The Corps doesn't have enough people. Searching for Muzan and the Twelve Kizuki across such a large area would be like looking for a needle in a haystack."

"What should we do, then?"

Everyone brainstormed but couldn't come up with a good solution.

"…"

Setsuna rested his chin on his hand, running through the Demon Slayer storyline in his head.

The main plot… Swordsmith Village… Infinity Castle…

He tried to analyze Muzan's goals and mindset.

"If we're having trouble finding the demons, why not change tactics?"

"Let's make them come to us instead."

"Huh?"

The Demon Slayer Corps was stunned.

"Make them come to us? How?"

The Kocho sisters leaned closer, curious.

"Do you know what Muzan wants most?"

Setsuna raised two fingers.

"First, he wants to find the Blue Spider Lily and create a drug that allows demons to walk in the sunlight, granting them true immortality."

"Second, he wants to destroy the Demon Slayer Corps and eliminate anyone who poses a threat to him so he can live without fear."

"Using these two points, we can devise a plan to lure him out."

Compared to humans, demons had faster reflexes, stronger bodies, better recovery, and powers akin to magic through their Blood Demon Arts.

However, they had one fatal weakness: sunlight.

Even Muzan, the progenitor of demons, couldn't overcome this vulnerability.

For over a thousand years, he had schemed to solve this problem.

At the same time, his extreme fear of death drove him to annihilate any potential threats.

After Yoriichi's death, he eradicated every swordsman who practiced Sun Breathing to ensure its extinction.

Cowardly yet cruel, violent yet cunning—this was the paradoxical nature of Muzan Kibutsuji.

"Oh, we've never really thought about Muzan's goals like that…"

"Now that you mention it, it makes sense."

Kagaya and the other Corps members nodded in agreement.

Setsuna's deep understanding of the demons left them in awe.

It felt as though he knew more about their world than they did.

Where on earth did he get all this information?

"In that case," Kagaya mused, "based on what you've said, there are two ways to lure Muzan and the remaining Kizuki to us."

"First, we find the Blue Spider Lily."

"Second, we use the Demon Slayer Corps as bait by deliberately exposing ourselves."

"Would that guarantee Muzan's appearance?"

"Smart!"

Setsuna gave him a thumbs-up.

Despite Kagaya's frail appearance, his mind was remarkably sharp.

"And the best option," Setsuna continued, "is to combine the two."

"Think about it. If the Demon Slayer Corps' headquarters held a rare, precious Blue Spider Lily capable of allowing demons to overcome sunlight, wouldn't that be irresistible to Muzan?"

Setsuna gestured animatedly.

"If he attacks, he could not only eliminate the Corps but also seize the treasure he's been searching for. There's no way he'd refuse, right?"

"At that point, he'll unleash his traditional tactics—bringing his entire family and minions, shouting something like 'The fate of the empire hangs on this moment!' as he charges at us."

"…"

Not only the Demon Slayer Corps but even the shipgirls were left speechless.

Commander, how do you know Muzan so well?

And this plan—why does it sound both dangerous and incredibly absurd?!

"I have a question!"

Kanae immediately raised her hand.

"Where can we find the Blue Spider Lily?"

According to Setsuna's plan, there was no way Muzan could resist the temptation of destroying the Demon Slayer Corps while also obtaining the Blue Spider Lily.

The problem, however, was that exposing the Corps' headquarters was simple—finding the Blue Spider Lily was not.

Muzan had spent over a millennium searching for it, and he hadn't even found a trace.

Many Demon Slayers had never even heard of its existence before now.

"I don't know."

Setsuna's answer was blunt.

"???"

Everyone stared at him like he was a demon himself.

"You just came up with such a detailed plan, but you don't know where to find the Blue Spider Lily?"

Shinobu's mouth twitched.

If not for Setsuna saving her sister, she would've wanted to smack him over the head a few times.

"The Blue Spider Lily only blooms during the day and only for a few days each year. What's worse, it grows in highly specific locations."

"I've only just arrived in this world—how would I know where to look?"

"..."

The group exchanged helpless looks.

No wonder Muzan had spent a thousand years searching with no success.

A flower that only bloomed in daylight? The odds of a demon finding it were as absurd as… well, as seeing a demon in the sun.

"Hiss…"

"This is a real headache…"

Kagaya Ubuyashiki rubbed his temples, deep in thought.

"The Corps doesn't have enough manpower to dedicate to searching for the Blue Spider Lily…"

"That said, the Ubuyashiki family has some influence. If we reach out to our contacts… But no, we'd need to be cautious about leaks—if Muzan found out, it would all be for nothing…"

He started considering how to find the flower as quickly as possible.

"Do you have any more information about the Blue Spider Lily?" Kagaya asked Setsuna again. "Like its preferred temperature, humidity, habitat, or flowering season?"

"If we miss it by accident, we might have to wait over a year…"

"Stop, stop, stop. You're overthinking it."

Setsuna halted Kagaya and the overly proactive Demon Slayer Corps.

"Our goal isn't to actually find the Blue Spider Lily. It's to make Muzan believe we have it. Why go through all that trouble?"

"Shinobu, go pick a red spider lily from the garden."

"Huh? Oh, okay!"

Shinobu scurried outside and returned with a red spider lily.

This was the most common variety, also known as Manjushage, said to bloom on the other side of the River Styx.

Its vibrant red petals curled outward in delicate arcs, exuding an eerie beauty.

Setsuna retrieved a bucket of blue paint from Richelieu's rigging and dunked the flower into it.

The petals and stem quickly soaked up the paint, turning entirely blue.

"Here you go—a Blue Spider Lily."

"??????"

The Demon Slayer Corps and shipgirls were dumbfounded.

What in the world?

Was it really that easy?

Could Muzan possibly be fooled by a flower dipped in paint?

"I already said our goal is to make Muzan believe it's the Blue Spider Lily. Whether it's real or fake doesn't matter."

Setsuna repeated himself and turned to Kagaya.

"The Ubuyashiki family has contacts in the shogunate and certain industries, right?"

"Uh… yes… uh, wait—yes, that's right."

Still stunned by Setsuna's audacious trick, Kagaya nodded mechanically.

"What's next?"

"Illustrious, take a photo of this 'Blue Spider Lily' and save it."

Setsuna tossed the painted flower to the shipgirl.

"Kagaya, contact newspaper editors and journalists. I want every newspaper to publish a front-page story over the next week."

"The headline should read:

'A wealthy foreign merchant named Setsuna is searching for the Blue Spider Lily to cure his sister's illness, offering a massive reward…'

"Make sure it mentions that we've already found traces of the flower and are working with the Demon Slayer Corps."

"And don't forget follow-up articles. In a few days, announce we've identified the flower's blooming period and location. Add photos to enhance credibility…"

For a moment, the room fell completely silent.

Everyone was in awe.

The plan was simply too advanced for them.

Muzan might be hidden among humans, but he would undoubtedly pay attention to major news events.

Once it hit the newspapers and spread through word of mouth, even if it started as a hoax, the sheer buzz could turn it into something believable.

A foreign tycoon searching for treasure? That story practically sold itself.

Even with his paranoia, Muzan wouldn't be able to resist investigating.

"How did you come up with this idea…?"

The Demon Slayer Corps and Kagaya were utterly floored.

Compared to Setsuna, they felt like naïve amateurs.

Here they were, earnestly trying to search for the real Blue Spider Lily like fools.

"Sociology and mass communication studies—it's fascinating, isn't it?"

Setsuna patted Shinobu on the head.

"Watch and learn."

"Muzan might have lived for over a thousand years, but he's just an outdated relic. We've got so much more information at our fingertips—getting him to take the bait will be a piece of cake."

"Just be ready. Once he steps out of hiding, we'll finish him off."

The shipgirls exchanged glances.

They couldn't help but feel sorry for Muzan.

"Commander, your imagination is… truly something else."