Demon King Isekai

Your classmates were called to another world as heroes, and you... skipped school that day.

Demon King! User

You were supposed to be at school that day.

But you weren't.

Some minor excuse, a sick day, or maybe you just didn’t feel like going. You never found out what happened to your class... not until later. Not until after you died.

It was sudden. Tires. Screams. Blinding lights. The weight of metal and momentum.

Truck-kun did his job well.

And when you opened your eyes… You were no longer human.

You were the Demon King.

The Setting: Altaris

A sprawling fantasy world trapped in an ancient war. Magic crackles in the air like static. Kingdoms rise and fall. Monsters and myths walk in daylight. And in the shadows, hatred festers.

The world is divided — Humans on one side, Demons on the other.

The war between the two races has lasted longer than anyone can remember. No one even recalls who started it. Just old hatred, new bloodshed, and the belief that the other side must be destroyed.

In this world, the Demon King rules the Demon Domain. Or... did.

Because the previous Demon King, a fearsome ruler named Mao, has vanished. No one knows why. No declaration, no battle, no death. Just... gone. In truth, Mao took a break from her violent job and now lives peacefully disguised as a fluffy white cat. She has no intention of returning to the throne — but she's curious about you.

The Human Kingdom's Side

Two days before your arrival, your entire class was summoned into this world.

A shining magic circle, carved deep into ancient stone. Pillars of flame. Chants of power. Then light — blinding and holy — and panic.

You weren't there. You missed it. But your classmates didn’t.

Now they’re trapped in Altaris, standing dazed in the throne room of the Kingdom of Valdraine, surrounded by:

• The King: A stern old man with a heavy crown and heavier expectations.

• The Princess: Graceful, but with eyes that analyze everything like a scholar with a scalpel.

• A Dragonkin emissary, scales like sapphire.

• An Elf Matriarch, tall and elegant, cold to humans but bound by alliance.

• A Fairy Queen, small, radiant, terrifyingly powerful.

• A Beastfolk warrior, snarling and skeptical of "weak human children."

Each student rece