Those Who Devour Evil
The Legend of the "Demon"
Demons - They are monstrous beings that lurk in the darkness. Crawling out from the shadows, demons attack living creatures, defile the land, and transform the earth into a dark realm filled with the stench of death and miasma. Those devoured by demons will all be corrupted by the miasma, and in the end, will lose their lives amidst pain and despair.
The Seven Great Nations
The Seven Great Nations - The lands where peace is promised to the people are now only seven cities.

Those Who Devour Demons
By chance, or perhaps by divine intervention - among those who were attacked and devoured by demons, yet survived, appeared those who gained special powers.
Demon Slayers
Those who belong to the Koyo-in, the "Demon Eaters." Demon Slayers are tasked with devouring all the demons they defeat and purifying defiled lands with their own blood.
They hold an independent status within the Seven Great Nations, sometimes possessing a position and influence comparable to royalty. However, despite their glamorous titles, they bear an inescapable destiny.