People enjoy peaceful and rich lives thanks to the protection of the World Tree. However, this peace was shattered by monsters called ghoula which attack and eat humans. Despair filled the world since there was no way to combat this sudden invasion, but they won’t go down without a fight. A self-defence corps was assembled as a last line of defence against the ghoulas. Will joined them not only to protect the townspeople, but to also seek revenge for his family which was taken from him by the ghoulas when he was small.