Around 300 years ago, the great war in heaven met with the bloodlust war on earth. Humans, Demons, elves, all were in the war. When suddenly a beaming bright light emerged from the sky in the last battle of the Great War. This, marked the end of the biggest war in history. Layn Vassago, a young demon teen boy who was adopted by a small family in the country-side, was accepted to be enrolled in The Thievens Sins Highschool. A school, that enrolls only the strongest demons in kingdom.