Reincarnation as a Great Demon Lord - Chapter 4

Chapter 4: The Great Demon Lord Meets the Doctor

The maid, Selen, said she would bring one of the commanders of the former Four Great Legions of the Demon Army, so I waited eagerly on my throne. I wondered which of the Heavenly Kings would arrive. Whoever it was, my overflowing Last Boss Aura would surely bend them to my will. I was brimming with confidence.

…However, the one who arrived before me was a blonde-haired, crimson-eyed little girl wearing an oversized white lab coat.

A loli… a loli?

To me, the sole female among the Four Great Generals should be a stunning, sexy beauty. This girl was beautiful, yes, but in a completely different genre.

…Well, no matter. Perhaps some generational succession had occurred while I wasn’t paying attention. Selen wouldn’t lie, and if this little girl truly is a former general, there must be a fitting secret behind her. Maybe she’s a fallen magical girl or something along those lines.

“...I feel like I’m being stared at very rudely.”

“Hmm…”

Damn. She noticed. I straightened up on my throne and re-formed a confident, menacing smile. A Final Boss must always appear inscrutable. One must sprawl arrogantly in their seat, wearing a cryptic expression.

“…Well, whatever. More surprising is that you’ve awakened now. My calculations rarely fail, but here we are.”

The little girl sighed. Ah, so she’s the type with a sarcastic personality. Interesting. A unique subordinate is always better than a dull one.

“I am the Great Demon Lord. I permit you to speak your name, child.”

“‘Child’? I’ve already lived for five hundred years, you know.”

Five hundred years! That means she’s lived since the early Sengoku period in Japan.

Ah, I see. A loli-grandma. That’s a remarkable trait. If she could return to her true form when serious, all the better.

Wait a minute… didn’t one of the Four Great Generals have such a backstory…?

“This body is only temporary. If that cold-blooded Hero hadn't destroyed most of my original body, I could have reconstructed myself properly.”

Cold-blooded Hero? Original body?

…Ah! I should have realized sooner! This loli-grandma is definitely one of the generals!

“My name is Arcelia. I’m a vampire. I was a general under the previous Demon King.”

Of course! It’s Arcelia, the ‘Black Blood Princess,’ one of the Demon Army’s Four Great Generals! Though her build differs from what I expected, her blonde hair and crimson eyes matched. I should have known.

Arcelia is a vampire and a mage, but most importantly, the Demon Army’s greatest mad scientist.

In Mythologia 2, she created experimental creatures, weapons, and inventions that tormented not only the hero but humanity itself. Her curiosity was boundless, ultimately leading her to attempt capturing the protagonist, only to be defeated—at least, that was her fate in the original story.

But here she is, alive… as a loli-grandma.

Exactly the kind of talent I want! Her attributes might be excessive, but the stronger the character, the better—especially for a high-ranking officer in my army. A spin-off protagonist-level character is just the right caliber.

“Arcelia-sama is a mage and one of the top three researchers in the Demon Realm—”

“Selen, I won’t have you repeat that. I’m not a mage. I’m a scientist. Don’t lump me with those nostalgic fools who contribute nothing to progress.”

Selen bows apologetically, though she doesn’t look overly remorseful. Interesting. She’s obedient to me, but surprisingly bold. I like that.

“A scientist, huh? Then what’s your specialty? What do you research?”

I already knew the answer, yet I asked. Arcelia seemed slightly surprised and replied:

“Magic Chemistry, Magical Engineering, and Magical Biochemistry. Well, I’m a genius in other fields too, and as a mage, I’m top-tier.”

The little girl puffed her chest proudly. Coupled with her doll-like appearance, she’s undeniably cute. If she’s to serve as a senior officer, she could use more gravitas—but having at least one adorable presence is fine. And her versatility matches the original—this is very promising.

“My research goals… well, that’s none of your concern. I’m just a scientist. I served the previous Demon King because he was the greatest patron in the Demon Realm.”

A mad scientist willing to serve evil for the sake of research… excellent. Her secrecy about her research goals also scores points with me. In the original story, her ultimate objective was never revealed, but I can imagine it was horrifically ambitious—even for a Final Boss like me.

And my Demon Army is an evil organization. What matters is competence. Morality, loyalty—irrelevant. In fact, mastering such individuals only elevates my status as the Final Boss.

“So, if I, the Great Demon King, can offer you at least what the previous king offered, or more, you’d serve me. Is that correct?”

“Yes. But it’s impossible, really. The current Demon Army is basically nonexistent. Only Selen and low-level monsters remain. And I’m only using the lab equipment in this castle, so don’t expect too much.”

“But I am here. I am the Great Demon King. Do not compare me with other kings. What can you offer my army? There’s no seat for the incompetent.”

I provoked her intentionally. It worked—Arcelia murmured, “Finally, someone speaks sense,” and her eyes glinted challengingly.

“You probably don’t realize, but I designed this castle and its throne. I copied the previous Demon King’s body to create yours. In a sense, I’m like your parent. Do you understand my capability?”

Ah, as I suspected. My body is a clone of the previous Demon King, crafted by Arcelia herself—a detail never revealed in the original story.

“Then… shall I call you mother?”

“Stop. Gross. Do you even know how vampires reproduce?”

I teased her a little. She glared. Ah yes, I remember from my previous life—their method involves drawing blood from virgins to create new vampires.

…Maybe that counts as sexual harassment. Better change the topic.

“So, Doctor, what is it you desire from me?”

“…First, I’d like you to supply power to this castle. If you can’t do that, it would disgrace the Demon King’s name.”

“I am the Great Demon King. I surpass all kings.”

Arcelia scowled, more aggressive now.

“This throne is the core of this castle, its cockpit. If you are truly the Great Demon King and deserve to rule this castle, concentrate your mind and pour your magic into it. If the castle responds, then, yes, I will serve you.”

“Very well.”

She looked doubtful, but a Final Boss doesn’t back down. And I had an idea of how the castle’s systems worked. Even the incompetent original king, Gaiselius, used some functions.

I sat deeply in the throne, palms on the armrests… and felt a connection between the throne and myself. But how do I infuse magic?

A choice appeared, like the status screen:

Release magical power? Yes / No

Of course, I chose “Yes.” A tremendous heat surged through my body. Blue-white flames rose from me—visible magic, I suppose.

“Amazing…!”

“More than expected… but where does this power come from?”

As expected of infinity-class magic. Selen and Arcelia were impressed, but I knew I could draw even more. I could envelop this entire massive castle in my power.

But for now, my focus is the castle’s internal mechanisms.

Arcelia’s boast wasn’t unfounded: a massive protective cloaking field, food production plants, weapon factories, and a secret weapon at the core—everything a mad scientist could dream of. These were never utilized in the original game, either due to the king’s incompetence or technical limitations. Now the possibilities are endless.

However, only one function can be activated for now—the most important one.

“—Time to fly.”

“Huh?”

Ignoring Selen’s surprised look, I reactivated the castle’s flight system. It required immense magical power, but infinite magic makes it trivial.

A deep rumbling shook the entire castle. Selen’s fearful gaze met mine, and when I nodded, she relaxed.

Arcelia understood immediately and stared in awe. Excellent. Now she knows the greatness of the Great Demon King.

After a minute, the shaking subsided. The castle stabilized in the sky. Success. Thanks to my Final Boss Methodology.

“Now, look outside the window. The moon floats above the clouds.”

I pointed toward the shattered window in the audience hall. Below stretched a sea of clouds, and above it hung a crimson full moon. Beautiful—the view of a sky castle.

Yes, the castle was flying. Its flight system, designed as a mobile fortress, had been dormant for ages—until I revived it. The only reason it was unused? Lack of magical power. But for the Great Demon Lord with infinite magic, this is trivial.

Even in the original story, the castle flew, but never so elegantly or stably—only I could achieve this.

Selen and Arcelia were speechless, impressed by my power. Perfect.

“Then, this castle needs a new name: I shall call it the 'Great Demon Lord's Sky Fortress.'”

Simple is best. Using this fortress as a base, my path as the ultimate Final Boss begins. The thrill of what I will achieve makes my heart race.

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SIDE: Former Heavenly King

Honestly, I wasn’t surprised or excited when I heard the Demon King had awakened.

The previous king had nothing particularly worth studying. Sure, his base demon traits were superior to other races—but that was it. Other traits were just copies of other races, leaving little to research.

I did prepare a cloned body and connected it to the castle’s core, but only out of obligation. I had no real interest.

But now…

This “Great Demon Lord” made my castle fly. The reality I had once given up on—the dream of seeing the castle soar through the sky—I can now witness.

It’s fascinating.

To fly this castle requires nearly infinite magic. Even the previous king, with hundreds of times the storage and output of normal demons, could not achieve it.

And the castle’s reactor is currently inactive. This king accomplished what none could, with no external assistance.

He must be drawing magic from somewhere else—something no previous king could do.

Moreover, he achieved self-awareness within minutes of awakening. Unheard of.

...I want to research him. I want to observe, test, and experiment. I want to know the texture of his skin, the flow of his blood, the fluctuations in his body temperature… I want to understand it all.

But no, Arcelia. Patience. Curiosity is sustenance, but excess will destroy you. You’ve lived 500 years; you’ve learned this.

First, I must ingratiate myself. The previous king provided resources and a lab in exchange for my service. I will do the same. Or offer myself if needed.

Someday, we will walk under sunlight. That is the ultimate wish of us vampires, formerly human—our singular goal for centuries.

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