Two hundred years ago, in the war between humans and demons, the demons were defeated. Many demons fled to a place called Shadow Valley, but it was very dangerous because there was an extremely powerful dark creature hidden in it. The dark creature was called "Ghost". This dark creature was terrifyingly aggressive and destructive. The people of the demon clan suffered greatly. In order to help the tribesmen leave here, two disciples of the demon elder started this journey.
Concept: How do humans and demons get along with each other?