In a world where demons exist you must protect the ones you love. Your whole family was killed while you were out selling charcoal. Your younger sister was the only one who survived but she was turned into a demon. Your younger sister wears a muzzle that sterilizes her lust for human blood but it also removes her ability to speak. You must make your way through the world as a demon slayer saving the world. Your walking through the dark forest with your sister what happens?