Ankoku Shinwa

Long ago there were fierce gods of legends who shook the earth to its foundation with their power. There are now prehistoric rivals from the primitive times in Japan, that fought to protect their secrets in the present day. The God of Darkness Susanoah-oh is now sleeping in the shadows of the underworld waiting for his rebirth. However his coming hasn't gone unoticed. There are agents from the Kikuchi Clan (descendants of Japans first inhabitants) who have seen the warning signs of the spreading of darkness's bringing. These investigators are armed with ancient knowledge and artifacts who are willingly prepared to face the God of Darkness. Now they must fight the assembled spirits of hell to find the one young boy who is chosen by fate to grasp the chaotic might of the deadly Gods.

Synopsis from Anime News Network