the world they currently live in is dominated by two races, the human race and the mazoku race. the mazoku are demonic creatures that once ruled their world, until they were all sealed away into a tiny box by a heroic angel 500 years ago. an age of prosperity and peace arose and human civilization blossomed. cities were built and nations were created. science advanced in some, while magic became the source of power for others. one day, a woman by the name of pandora accidentally opens the box containing all the demons, releasing them all from their imprisonment, darkening the skies and dooming human race to extinction at the hands of the mazoku. in a desperate attempt to save humanity, the demon king chestra, who was also released from that box, was sealed again. pandora's two children, who were fathered by chestra as part of the deception used to trick her, were separated as infants; one was taken by the mazoku, the other remained with her mother. in order to keep the world safe, the box that sealed the demon king, now named pandora's box, was sent far away, and the key that opened the box was also sent far away, in hopes that even if the mazoku would ever get their hands on one, they would not be able to make use of it. all the demons who were released then headed north, and occupied the northern-most continent and called it their capital, hameln. now humans fight a never-ending war against the demons in order to survive. pandora's children - one who lives with the humans, and is hated by all those around him; the other, living with the mazoku who have never shown her any sign of affection - are destined to be reunited and bring an end to the war, one way or another.