Muzan Kibutsuji Explained: The King of Demons in Demon Slayer

Every demon in Demon Slayer traces back to one person. Muzan Kibutsuji, the King of Demons, is the first demon, the maker of all the others, and the villain the whole story is built around. Here is who he is, where he came from, and the one thing that can kill him.

Who is Muzan?

Muzan is the original demon and the strongest being in the series. Demons are created from his blood, and he can kill any of them from a distance whenever he likes, which is why the Twelve Kizuki and every lesser demon obey him without question. He spends most of the story hiding in plain sight, shapeshifting into ordinary people so the Demon Slayer Corps can never find him.

His origin: a dying man and a doctor

Muzan was born during the Heian period, over a thousand years ago, as a sickly human who was not expected to live to twenty. A doctor tried to save him with an experimental medicine built around a rare flower, the blue spider lily. Muzan believed the treatment was failing and killed the doctor. Only afterwards did the medicine take hold, curing his illness and turning him into the first demon.

Muzan became a monster by accident, then killed the one man who could have explained what he had become. He has been chasing that lost knowledge ever since.

The blue spider lily and the sun

The transformation gave Muzan near-immortality with a single catch: sunlight destroys him. He becomes obsessed with finishing what the doctor started, hunting for the blue spider lily in the belief it will free him from the sun forever. He never finds it. The flower only blooms in daylight for a few days a year, so a creature who can only move at night was never going to stumble across it.

His only weakness

Muzan can regenerate from almost anything, restructure his body at will, and outmatch entire teams of Hashira. The only reliable ways to hurt him are sunlight, the special Nichirin blades that can behead a demon, and the wisteria-based poisons developed by Tamayo and Shinobu. Everything the heroes do is designed to buy time until dawn.

How Muzan is defeated

Without spoiling the specifics, the final battle is a race against the clock. Tamayo's drugs weaken and age him, the surviving Hashira and slayers keep him pinned and exposed at enormous cost, and the sunrise does the rest. When the light finally reaches him, the King of Demons crumbles to ash. His last act is a desperate attempt to keep demon-kind alive by passing his blood to another.

Building a Muzan-style villain OC

• ▹Give them one obsession. Muzan works because everything he does serves a single goal. A villain with one clear want beats one with vague evil.
• ▹Make them hide. The scariest thing about Muzan is that he looks like anyone. A demon OC who blends in is more unsettling than an obvious monster.
• ▹Pick a hard limit. Even the King of Demons has the sun. Give your villain a real weakness and the story writes itself.

Our Demon Slayer OC creator lets you build a demon with slit eyes, a Blood Demon Art and a tattered look in a few clicks.

Muzan FAQ

Why does Muzan disguise himself?

Because the Demon Slayer Corps has hunted him for centuries. Blending in as a husband, a businessman or a child lets him move around in daylight hours and stay one step ahead of the people trying to kill him.

Is Muzan stronger than the Upper Moons?

By far. The strongest of the Twelve Kizuki, Upper Moon One, is still only a servant. Muzan created them all and can end them with a thought.