When she was still just a girl, Kotoko was kidnapped by yokai (spirits). They made her into a powerful intermediary between spirits and humans, but this power came with a price: one eye, and one leg. Now she's falling in love with a young man named Kuro, who is also special: an incident with a yokai has given him healing powers. He's surprised when Kotoko asks him to team up to handle renegade yokai, preserving the thin line between the human world and the spirit world.