She is Yato's former Shinki. "Nora," meaning "stray," is how the gods call any Shinki who has many masters and many names. Because of this they have bad reputation and are target of prejudice by the gods, who nevertheless use them for works they don't want to use their own Shinki for (dirty works, for example). This particular Nora was named Hiiro by Yato, and she still offers herself to be used by him, though he always resists. In chapter 38, Yato severed her contract with her and she is not longer his Shinki.