Senyuu.

Long time ago, there lived an evil being who reigned over the world through fear, called Satan Rchimedes. He invaded the human world with his many demon underlings, spreading madness and chaos everywhere. One thousand years ago, this menace was sealed by the hero Creation, and peace returned to the world. Now a hole has opened up and the demons are running amok. It's up to the descendants of the hero to kill the demon king.