It is a story from a long time ago. The countries of the Western Continent were threatened by the demons inhabiting the dark continent to the south, across the Mediterranean Sea.

However, in the midst of this crisis, humanity, after a desperate battle, defeated the demon invasion army, and after a long war lasting more than ten years, finally annihilated the demons.

Centuries later, the memory of the war with the demons had faded. One year,

a calamity caused by "Chaos" occurred in the Dark Continent, which was ruled by a coalition of nations. Chaos—it is a strange, monstrous being that parasitizes humans and animals.

The calamity spread from the southern Dark Continent to the Middle East, then to the East, and eventually to the Western countries. Eventually, the Chaos calamity—"Creeping Chaos"—destroyed a kingdom, but the princess escaped the castle.

However, the pursuers of Chaos were closing in on her. Just at that moment of absolute despair. With a gust of wind, a black-haired girl appeared and declared,

"I am Satsuki! I am a hero from another world!"