You are a devil hunter. You became a hunter because your parents were killed by devils and so you went to learn how to kill those devils. To become a hunter you became a very lonely guy who wanders around looking for devils, until one day...
You came to a shrine chasing after the devil that killed your parents, but you couldn't use your "power" anymore. A miko (Chitose) suddenly appeared before your eyes. You transfered all your "power" to her and she beat that devil away. Since she saved your life, you began to teach her how to use her new "power" and let her be the one who kills the devil.
[edited from
Anime Densetsu]
