Yurine is the youkai-priestess for Tokyo. Ekou was the Karas for Tokyo during the Edo period, but when he turned down the "shadow path" she was forced to select new Karas. All Tokyo Karas since Ekou have fallen before him, and Otoha is Tokyo's last hope. Yurine holds the secret to a dark force empowering Ekou, but its exact nature is yet to be revealed.
There is one Yurine for every city.