Musashi is a teenager living under demon rule. As children, he and his best friend made a promise: to become the greatest warriors in the world and overthrow the demons. But life intervenes, and five years later, he finds himself about to become a miner. He''s being called a prodigy with a pickaxe, and he''s almost ready to settle for a life of labor. Yet he can''t shake the feeling that he still has a responsibility to act... and, soon, the injustices of his world will force his hand.