With her father murdered, and her mother and sister abducted, Ason Asaki is now the leader of her land. She hunts down the person responsible for the crimes against her family only to find out he is a demon that Asaki is no match against. She is saved by Mikazuchi and Hisui who use their powers to protect her. Mikazuchi makes a contract with demons to borrow their strength and Hisui is actually a sword in human form that Mikazuchi uses to destroy evil. Mikazuchi is looking for the ten demons responsible for the destruction of his town and massacre of its people. Both sides soon realize that their fate is intertwined with each other.