Hiiragi is a Yokai that has been forcibly tied to an old storehouse once owned by a prominent family. She was tied there with a rope she could not break and forced to curse anyone who tried opening it.

As it turned out, Natori once met her while he was a child, putting bandage on her wounded arm. Natori would later return with the intent of exorcising her, having forgotten who she was. But, thanks to interference by Natsume, her life was saved, and she took on the new position as Natori's newest familiar after everything was cleared up.