Sai Youki

As humankind stops its evolution and goes towards extinction, Akane and her group aim to become masters in order to obtain the scripture of legend. When Akane is asked to get rid of evil spirits in a village she stops by, she and her companions find an unconscious young man in an abandoned mine where evil youma lurk. His legs have been chopped off and he lacks the orb that identifies him as a human being. One of her companions realizes the truth—this young man is the abandoned prince of the country of Sai. To the surprise of her companions, Akane makes the decision to take the man with them on their journey—where they await youma unlike anything they've ever seen.

(Source: Kodansha, translated)