The Last and Only Way
During the last expedition, I learned the Demon King's secret.
Before every battle, the Demon King hid his weakness. Always in the same place—and that place was the dungeon I had just stepped into.
Even while selecting and training the party candidates, I had continued researching that secret. What weakness could be so vital that the moment the Hero party crossed into the Demon Continent, the Demon King would hide it away in a concealed dungeon?
I found a clue in an old bard's song:
When the primordial moon blushes red
All living things become as one
Demon, dragon, beastfolk, human alike
Into a sleep deeper than death
Together they sink away
In short, it meant everyone held hands and died together.
What that actually meant was this:
In his final moment, the Demon King would unleash the Magi of the Red Moon—a self-destructive attack that poisoned humans and demons at the same time. The Demon King's Castle and the surrounding territories would be reduced to ash in an instant.
Only the Demon King himself could survive that attack.
Humans simply died. Demons were revived. Situation resolved.
The problem was that even demons could not be revived if they were still children who had not yet undergone the Adult Ceremony.
So what was the Demon King hiding?
His only weakness—and his greatest treasure.
He was protecting his only daughter from the Magi of the Red Moon by sealing her inside a dungeon.
This dungeon, to be exact.
The dungeon was not deep. Before long the end came into view, and the entrance to the final chamber appeared ahead.
I affixed a spring-wound device to a stalactite. I had already planted thirty of them on the way in; for a moment I worried I might have overdone it.
Didn't matter.
I had no intention of walking back out anyway.
I took a sphere from my pocket—a hard-won orb of Magi. When I crushed it in my fist, thick Magi burst free. I smeared the stuff liberally across my chest and shoulders and walked toward the end of the dungeon.
There was a modest cavern. A stalagmite rose at its center, and behind it I felt a small presence.
I called the secret by name.
"Princess?"
No answer.
"I come by order of the Demon King. I am here to escort you to safety."
A pale face peeked out from behind the stalagmite.
"Who are you?"
"Count Juin, heir of House Marcus."
I watched her nostrils twitch. She was reading the Magi on my body.
Noble houses carried their own distinctive Magi scent. What I had smeared on myself was unmistakably the Magi of a high-ranking noble. I had gone through hell to obtain it during the last expedition.
"I've never heard of that house."
She was only seventeen. There was only so much information she could have.
"We govern a secret and critical territory. Even within the Demon King's Castle, very few know of us."
That much was not a lie.
"Even so, I've never seen you before. If you were a noble, shouldn't you have paid your respects to me at least once?"
"I had the honor of meeting Your Highness when you were still in the nursery. After that, the border situation grew so urgent I could not leave my lands."
That was not a lie either.
"Father told me not to move from this dungeon. He said it was the safest place in the world."
"He did. Until a problem arose."
"What problem?"
I flicked my fingers where she could not see.
The spring-wound devices activated.
KRAKOOM—KRAKOOM—KRAKOOM—
Heavy explosions detonated in sequence, shaking the dungeon.
GRRRRRRRRRRR—
Lava boiled up through the cracks that split the dungeon floor.
"Eeeek!"
The princess toppled as the dungeon lurched. I sprang forward and caught her across my knee.
"There's no time. We have to get you somewhere safe—now."
She looked toward the opposite entrance of the dungeon—the side that led to the Demon King's Castle.
"Not that way. Do you want to die at human hands? Then who will greet the Demon King's resurrection?"
"Father's resurrection?"
"The Demon King is dead."
From here on, the lies began.
"Father's dead? That's impossible…"
I reached into my pocket and produced the most spectacular lie of the day.
"Before His Majesty drew his last breath, he commanded me to deliver this to Your Highness."
It was the Demon King's bracelet.
The princess would know exactly what that bracelet meant.
A treasure that never left the Demon King's body until the moment of his death—and it was now in my hand.
"Papa…"
Her eyelids trembled. Her clear eyes flickered like candle flames in the dark of the dungeon.
I slipped the Demon King's bracelet around her neck.
"Overcome your grief. The fate of the demon race rests on Your Highness. Do you understand? Only if you live will the Demon King return."
"……"
"From this moment on, Your Highness must conceal her identity."
"What does that mean?"
"Because the place we must hide from now on is—"
I spread my palm and opened a portal.
"—human territory."
I scooped her into my arms and walked toward the curtain of light.
She stared up at me with round eyes.
The world brightened, darkened, then flared white again as the portal spat us out onto a low hill.
Wind blew. The fresh scent of grass swept across my forehead.
In the opposite direction, the border of the Demon Continent was visible.
It would take a long time to reach my territory from here.
She gazed at the landscape with her mouth open.
"This is human land?"
"It is."
"Can't I just hide somewhere on the Demon Continent?"
"Your Highness already knows why that is impossible."
"I do?"
"Do you think the seventy-two successors will simply leave you alone?"
When the Demon King dies, a successor appears. That is the law of the demon realm.
"They will have to kill Your Highness to claim the Demon King's Castle. Right now, demons are more dangerous to you than humans. Only Your Highness can resurrect the Demon King."
"Mother would never allow it!"
"Only the Demon King can save demons from the Magi of the Red Moon."
"…Mother is dead too?"
I calmly delivered the final lie.
"Yes."
Tears that she had been holding back finally welled at the corners of her eyes.
"I can't trust you."
"How else could I have entered the dungeon where Your Highness was kept? It was a secret known only to the Demon King, was it not?"
She lowered her head.
Because that was true.
It had been a dungeon so secret that even his most trusted subordinates had not been sealed away with the princess. An ancient ruin known only to the Demon King and the Demon Queen.
I leaned my lips close to her ear.
"There is no time. The seventy-two successors to the Demon King are already hunting for traces of Your Highness."
"I'm a demon. How am I supposed to live in human lands?"
"There are already demons living there."
"…You mean the slaves."
She knew that much, then.
Demons existed on the human continent as well. Most of them were slaves—prisoners of war, criminals captured while raiding human villages, female demons hunted down on the Demon Continent.
"You're telling me to live as a slave?"
"If we are to conceal your identity, it cannot be helped. But do not worry. I will always be at your side."
"Until I undergo the Adult Ceremony?"
This was getting easier. She had found the justification herself.
"Exactly. Your Highness carries the Demon King's blood. Once you awaken your power with the Adult Ceremony, you will surely be able to resurrect him."
That much was true.
And it was also the three years I had secured for myself.
"But how am I supposed to live like a slave?"
I stretched out my hand and pointed at the portal.
"If you wish, go back. The gate is still open."
"Lord Marcus?"
"If Your Highness chooses to walk toward the successors' blades yourself, I will not stop you. I will simply end up serving a new Demon King."
"Papa……"
"My territory is safe. Until the Adult Ceremony, I will serve Your Highness."
"Won't that put you in danger too, Lord Marcus? Because of me?"
Of course it would. Any number of complications would arise.
But at least I could stop the Demon King's attack for certain.
Because I held his only weakness in my hands.
"I accept that willingly."
The princess bit her lip.
"Then… I'll be in your care."
"It is a decision that will require resolve."
"I know."
"You must forget everything about life in the Demon King's Castle."
"I suppose so."
"Very well. Then I, Marcus, will from this moment forward serve Your Highness as a slave."
Her shoulders trembled.
"Please take care of me. I'll leave everything to you, Lord Marcus."
I gently wrapped my arms around her shoulders.
Someone would ask, no doubt. Wasn't kidnapping going a bit too far?
What was I supposed to say to that?
Eighty million people had already died at the Demon King's hands.
It had gone on for fifty years, it would continue, and eventually the extinction of the human race could become reality.
With the Hero parties failing one after another, what was I supposed to do? Just sit and wait?
For death and extinction?
What would you have done?
If the last remaining way to save countless lives was to take the enemy's daughter hostage—
"Shall we go, Princess?"
I opened the portal once more and set out with her toward my territory.