Hiizumi Enjin

Japanese name:

比泉 円神

The main antagonist. A youkai who is determined to destroy the barrier protecting the city for unknown reasons. Later it is revealed that he has no physical body and is, in fact, possessing the body of Gin who happens to be Ao's older brother, a wolf-youkai who was best friends with Hime and Akina. When Akina first met Enjin in the anime, he hesitates about using tuning on him because he knew that if he were to use the tuning ability not only will he send Enjin, but he will send Gin's body as well as Gin's spirit, which still lives in his body, to the youkai world.

Wikipedia