Kanade

was the guardian miko of Hōraijima, a place where demons and humans lived in harmony, and consequently the birthplace of many hanyō.

History
However, every fifty years, the time barrier would weaken, and demons from the mainland would attack. Among the bloodthirsty horde, were the Four War Gods. Kanade fought during those battles and managed to seal the War Gods' powers in four sphere, before throwing herself into the Cauldron of Resonance, at the cost of her life. Unfortunately, the Four War Gods figured that by throwing half-demons into the cauldron, they could regain a small portion of their powers.

Fifty years later, she reappeared as a glowing green orb at the bottom of the Cauldron of Resonance when Inuyasha and Asagi was thrown into it. She gives Inuyasha her blessings and the little that remains of her life force in order to allow him to escape the cauldron. In return, she asks him to save the children that are on the island. She also gives him the container holding the power of the Four War Gods.

Trivia

 * She mainly appears in the movie as a glowing green firefly that speaks.
 * The meaning of Kanade's name, "play music," likely refers to the song that she taught to the children of the island.