Onto every nation in the human world I dropped a monolith: a twenty-kilometer black object cut to the shape of the country.
Humans being greedy, there was no scrap of land anywhere that belonged to no country at all.
So the land of the human world was buried under monoliths, completely.
I am in the Demon Realm.
We speak of the human world and the Demon Realm, but the two are not situated in separate worlds or separate dimensions or anything of the sort. They are ordinary connected land; only the territory differs.
Why, then, are they given such grand names? Because the human world is bright land, always lit by the sun, and the Demon Realm is dark land the sunlight never reaches.
This planet's period of revolution about its star and its own period of rotation happen to have locked neatly together.
In short—to put it in Earth terms—the human world is always noon and the Demon Realm is always night.
The reason I have suddenly presented this planet's geography in a monologue is that a visitor is about to appear and lodge a complaint regarding my geographical handiwork.
—DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM DOOM!
A tremendous shaking and din came from every direction around My Castle.
The monsters of the Demon Realm were storming My Castle all at once.
They charged, they threw themselves bodily against it; some breathed fire, some flung magic.
"Ohhh dear. It's pointless, though."
I have set My Castle in an indestructible state, so nothing anyone does can possibly break it. Nor will its doors ever open unless I intend to admit the visitor.
Not knowing this, the monsters were flinging themselves at My Castle with all their hearts.
The one who had sent them was the Great Demon Lord.
He had once ruled this Demon Realm as the Demon Lord, but he was gravely wounded in battle with a Hero and had to take a long dormancy in order to recover.
At that time he installed a substitute and made that one the Demon Lord.
But since that on its own would damage his original dignity as Demon Lord, he positioned himself as the Great Demon Lord.
Incidentally, the monsters I sent into the human world have been wiped out to the last, crushed under my monoliths.
So the monsters the Great Demon Lord ordered to charge My Castle are ones newly arisen in the Demon Realm.
The DOOM DOOM DOOM had gone on quite long enough to be a nuisance, so I floated the monsters high into the sky and burst their bodies into a fireworks display colored in blood.
The monsters' filthy blood came down on the earth of the Demon Realm like a summer squall.
I did not need to watch it directly; omniscience shows it to me perfectly well.
"Splendid~!"
Eyes closed, stroking the Mofu on my lap, I savored the bracing scenery now decorating the outside of My Castle.
Then I opened the castle doors and admitted the one figure left standing: the Great Demon Lord.
Before long the Great Demon Lord appeared in the throne room.
"Demon Lord, what in the world has happened while I slept— …who the devil are you?!"
A human child like me was sitting high and mighty on the throne where the Demon Lord ought to have been, and the Great Demon Lord recoiled hard enough to arch his upper body backward.
"I am [The Omniscient, Omnipotent, Strongest, Invincible, Absolutely Superior One]. The Demon Lord, I killed."
"Wh-whaaat?!"
The Great Demon Lord is a humanoid demon, with a pair of jagged pitch-black horns rising from his head like the zigzag of a lightning-bolt symbol. In the middle of his solid black eyes, vertical yellow pupils like a hunting animal's glitter. His skin is corpse-white, and his black nails are long and sharp as knives.
The pitch-black robe he wore was worked with solemn gold ornament, advertising his rank as king.
And there he stood, still unable to swallow the situation, gaping vacantly.
"What are you talking about, boy. You are plainly nothing but a human child. And you killed the Demon Lord? That one was the higher demon I trusted most, the one I called my right hand. Stronger than any but me, and cunning with it. There is no possible way he lost to some nonsense-spouting whelp like—"
"Ah, I didn't fight him. He was so frightened of me that he flew off, so I just killed him remotely. Rather one-sidedly."
"…And the Four Heavenly Kings?"
"Also all killed by me."
"Impossible…"
The Great Demon Lord's mouth would not close.
I propped my cheek on the throne's armrest and tossed a few words at him.
"So. What do you want?"
"Wh-what do I want?! This castle is mine to begin with. Give it back! And I have a mountain of things to ask you. The human world has become utterly incomprehensible while I was asleep. What are those black walls?!"
I let my brow furrow a little at the Great Demon Lord's manner of speaking.
The Great Demon Lord glared back at me, as if to match me.
"This castle is mine now. I took that fragile little castle of yours and worked on it until it cannot be broken by anything. It is no longer a castle the likes of you could build. Therefore it is mine. And even had I not touched it, if I say it is mine, it is mine. Also, the black walls in the human world are monoliths."
"Your explanation is sloppy! Set the castle aside for the moment—what is a monolith? Explain it so that I can understand!"
"Your attitude is too big. 'Please explain,' surely? A monolith is a twenty-kilometer black object cut to the shape of each nation of the human world. It is made of matter that cannot be interfered with, and I created it in order to render the land of the human world useless."
"Wait, wait, wait! Why? Why render the human world useless? I had my monsters invading precisely in order to take the human world into my hands. It has all been ruined. What need was there to do such a thing?"
"No, there wasn't any need or anything. It didn't matter either way, so I dropped monoliths for a bit of a diversion."
"Haaah?! Do not mock me! And what became of the monsters that had been in the Demon Realm all along?"
"I sent them into the human world, and they got flattened along with everything else when I dropped the monoliths."
The Great Demon Lord took two steps back and pressed his right hand to his forehead like a sun visor.
"Ah. Is that so… I seem to be getting dizzy…"
"Shall I make it easier for you? I mean by killing you."
"Do not mock meeee! I will not forgive you, boy!"
The Great Demon Lord straightened himself and began raising the density of the magic contained in his body. He can at least turn killing intent on me, which makes him more promising than the Demon Lord who ran. Whether it is wise is another matter.
Faced with the Great Demon Lord, I did not so much as shift out of my cheek-propped slouch.
I carried on the conversation with no regard whatever for the Great Demon Lord's killing intent.
"Hey. No offense, but isn't this your fault?"
"From a human's point of view, of course we are a monstrous evil!"
"No, no. I don't mean evil because you're the Great Demon Lord, or evil because you invade the human world. That's not the sort of thing I mean."
"…Hm?"
"I mean, I can erase the monoliths, and I can bring back every single dead monster too. But you can't, right? That's your fault, for being feeble. And anyway—you were asleep, weren't you? You can hardly complain about anything I do to you. You allowed the current situation to come about, and you can't do anything about it now either. So in the end it's your fault, for being useless."
The Great Demon Lord's killing intent vanished. His magic density returned to normal. Then he shook his head hard, as though he had been half-asleep until this moment, and brought his mind into focus.
"Ah—I was so startled that my sensibilities had gone human on me. Of course there is nothing for it but to take it back by force!"
The Great Demon Lord's murderous intent and magic density leapt sharply upward.
I stopped propping my cheek—and slumped back thoroughly against the backrest.
"Go ahead. Do whatever you like. Show me your strongest magic. If you have some really outstanding dirty trick, feel free to use that too. But if you do anything halfhearted, I'll erase you on the spot."
No blood flows in him, so his face did not redden—but the Great Demon Lord's face, demon though he is, took on the aspect of a raging ogre.
"As you wish—I shall destroy you with my strongest magic! Along with this entire planet!"
A black sphere of energy formed in the palms the Great Demon Lord thrust out before him, swelling steadily larger. Then, in an instant, it snapped back to its original size and grew huge again.
Three repetitions of this produced an extremely concentrated sphere of energy.
"ALL-PHENOMENA ANNIHILATION BURIAL OBLIVION BLAST!!"
A sphere of darkness some two meters across came flying at me, reducing everything in its path to nothing as it went.
Had it been fired at a star, it would have erased even the star.
"Not bad."
I blew a puff of breath at it, and the All-Phenomena Annihilation Burial Oblivion Blast, or whatever it was called, went back the way it came, toward the Great Demon Lord.
"What?! Impossibleeeee!!"
The Great Demon Lord was annihilated, the blast overwriting the space he occupied.
Afterward the fearsome black sphere touched the absolutely indestructible wall of My Castle and vanished.
"Ah—the Great Demon Lord is from this Demon Realm, isn't he…"
Onto the Demon Realm I dropped a monolith, a twenty-kilometer black object cut to the shape of the Demon Realm's land, and then teleported My Castle, with me and the Mofu inside it, to the top of that monolith.
"Magnificent. Magnificent!"
With that, the whole of this planet's surface was covered in monoliths.