Humanity is on the brink of extinction due to an attack from the demon race. The humans searched for historical and religious books to learn how to defend themselves against the demons, they found out that 6 races exists in different realms other than demons. A kingdom was built with a fort made of stone and salt to keep the rest of humanity safe. Showda a boy who was born half human and half demon is training in the academy to fight and reclaim the human realm from the demons.