Shinto
I was typing this as an answer to Jim's comment, but I might as well make it a post and be done with it. I don't really have much time to spend hours reading on religion in ancient Japan, interesting as it is. So I'll just start typing and see what comes out of it.
The gist of the issue is that Shinto was usual local animism, and the introduction of Buddhism with their holy ascetic monks and sutras and shit basically killed Shinto and replaced it for all purposes. Shinto animism was just your typ...