The Demon King's Qualification

My head was spinning, and my stomach churned. It felt like I'd been force-fed food that refused to digest—an utterly unpleasant sensation.

"Little brother, are you okay?"

Ash's voice reached me faintly. It still felt awkward that she was worrying about me, but right now, it was fine to lean on her.

"Sis, help me up, would you?"

"Of course. That last strike must have drained an enormous amount of mana."

"...Yeah, looks like it."

It wasn't really because of that, but there was no need to correct her. I couldn't exactly say it was the side effect of absorbing the demon that had been inside Joshua.

Archdemon, huh... It's on a whole different level.

As always, I couldn't absorb the demon right away. It was so massive and rough that it was seeping into my body slowly. Thanks to that, the demonic energy was hitting me hard.

"Master. Are you alright?"

"...Feels like I'm dying."

"Mammon's one of the demons qualified to become king. Like, the biggest of the big?"

"That 'qualification' thing... looks like I just absorbed it."

".........Pardon?"

"I didn't know either, but it worked."

"...A human gaining the qualification? That's impossible..."

Since the dawn of demons, there had only ever been one king. A being from legends and myths, whose name wasn't ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠even known. The lord of the Myriad Demon Hall, ruler of a portion of the primordial chaos—the King.

Even those qualified to become that king were few and far between. Naturally, such qualifications were granted only to the mightiest demons.

Until I'd fully absorbed Mammon's rank, that is.

Maybe the Seal of Original Sin... is even greater than I thought.

Until now, I'd seen it as just a trait that erased demons and absorbed their power. But now it seemed it could absorb their very rank as well.

"If I absorb all the other archdemons like this, I might end up as the demon king myself."

"...You as the demon king? I can't picture it, but it sounds fun."

Yeah, a mere mage like me at the pinnacle of demons? The demon king was a myth anyway, so it was absurd talk.

"Anyway, feeling better now?"

I was leaning against the wall, catching my breath, when Ash, who had approached me, asked.

"...Yeah, pretty much recovered at this point."

The absorption was still ongoing, but it was fine for daily activities. First things first, we had to deal with the collapsed Joshua.

"Hoo... So Father passed away?"

"No. He's still alive."

Damn, he really was something. I'd stripped him of every buff imaginable, and he survived that?

Or maybe, as an 8th Circle mage possessed by a demon, dying in one hit would have been weirder.

"...In that case, I'll finish him off."

I let out a deep breath and drew the sword from my waist. As I approached Joshua to stop his still-beating heart—

"Whoa, you're gonna kill him?"

"He's demon-possessed, isn't he? No choice but to put him down."

"No, it'll be fine. I don't sense any demonic energy from Father anymore."

What the hell was this frustrating, sweet-potato-like conclusion? She wanted to spare the man who'd tried to kill his own kids—including her—to grow his power?

Was that even a sane judgment? Logically speaking, even if the demonic energy was gone and he was back to normal, he was still dangerous. And there wasn't just one demon in the world named Mammon.

"...Hm, you wouldn't know, would you?"

"Pardon? Is there something else I don't know?"

First Celine, now this—what, was I that out of the loop? No wonder I'd been ignored my whole life in the family.

"Don't you remember your childhood?"

"My childhood?"

"The year before you turned ten."

The year before I turned ten. Unfortunately, I had zero memories from before then. I'd possessed this body at age ten and lived ten years since. Anything prior was not just fuzzy—it was completely blank.

"Father used to be a warm man."

".........Pardon?"

"You might not remember, but he doted on us terribly. He'd scold Felix harshly if he misbehaved."

And that man turned into someone the family overlooked any scandal for, as long as he had talent?

"His loyalty to the imperial family was beyond question. That's why His Majesty restored the title 'Northern Blade'."

The image of Joshua in my head clashed violently with that. The guy had been brimming with ambition like he wanted to be emperor himself.

"It started that day. The year you turned exactly ten."

The day I'd possessed him.

"Dragons and barbarians from the north launched an assault."

"...An assault?"

"A massive one. The strongest and most ferocious in nearly a century."

Dragons and barbarians never allied. Both races were too arrogant, convinced they were supreme, to join forces. Dragons barely cared about the human world anyway.

For a thousand years, since the empire's founding, they'd never once united.

Until then. For the first and only time in history, the two races joined hands.

"The Black Horn, who unified the fractured barbarian tribes, allied with the Silver Dragon, lord of the dragons at the time."

"......Pardon? Then how ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠did our family survive?"

"Haha. You think we lost, obviously."

"Well, dragons involved? Even the empire would be ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠in trouble."

Barbarians didn't wield auras, but their physical prowess was freakish. Elite warriors and chieftains hit at least 7th Core, some 8th or beyond.

And even without the barbarians...

Dragons were arrogant, but their power justified it. Transcendent beings who wielded 9th Circle magic just by existing.

So if dragons and barbarians allied, even the mighty Vergilius County...

Defeat was the logical outcome.

"But we won."

"............I really don't get it, Sis."

"Father used a forbidden tome from the family vault."

The title she mentioned next was one I'd heard of.

In the game, when you tackled the northern storyline, it was a key item. Sealed with the archdemon Mammon, and a cheat artifact you had to keep from the enemy via quest.

Though, 'contract' or not, it was obviously unequal.

Demons hated equality. They casually wrought destruction for their own gain. That was the common view of demons, backed by their history.

Lilia beside me was the exception.

"...So in the end, Father used the tome to repel the enemies?"

"Yes. Though killing the barbarian chieftain and breaking the dragon lord's horn was the best he could do."

That alone proved his immense power back then.

The dragon didn't come back after its horn broke, so the gap must've been that wide.

Maybe Mammon wanted us because Father had burned through so much power then. It had no choice but to help, but it'd expended a lot.

"But after that day, Father changed. Into the man he is now."

"......I see."

It made sense. Borrow a demon's power, pay the price—that was par for the course.

But still... spare Joshua?

That doesn't add up either.

No, saving him was fine. But ensuring he couldn't cause more trouble...

"Lilia. You can impose forced restrictions by expending demonic energy, right?"

"Of course. Shall I help?"

"Please."

I lightly placed my palm on Joshua's chest. Just as Ash moved to stop me—

I subtly manipulated the demonic energy inside me.

—Woooooong!!!!

A device I can detonate anytime I want, if needed.

Since I was keeping him alive, a basic insurance policy was wise. I couldn't fully trust a Joshua who hadn't fallen like Ash had.

"You okay?"

"Yeah. Just confirming the demonic energy was fully gone."

I flashed a casual smile and slowly stood.

"Ugh... I'm seriously gonna die. This is exhausting."

Operating mana and demonic energy simultaneously while fighting Joshua? Of course I was wiped.

If I wasn't exhausted, that ‍‍‌‌⁠​​⁠‌​​‍​​‍​‌​⁠‍‌‍⁠⁠‌⁠‌‍‌‍‌‌‌‍⁠​‌​‌​‌‍‌‌‌⁠‍​​‌‍⁠‌‌⁠⁠would be weird. Coming home to rest, only to wreck myself worse than at the academy—what a trip.