I started reading a book which I would say is pretty obligatory reading for everyone interested in this subject. It's The Catalpa Bow: A Study of Shamanistic Practices in Japan by Carmen Blacker.

It's very easy to read and engaging and seems to have a lot of information that is very relevant to Touhou. So far these include:
- Reimu means a divine reveleation in a dream. It was thought that kami most commonly appear to human in dreams, and a reimu is a dream where a kami appears.
- Noh theater, besides frequently having explicitly spiritual and magical themes, has features that suggest it is an evolution of shamanic practices.
- The Okina noh character is considered a kind of generic form of a kami or ancestor spirit. The titular Okina play is thought to bring good luck when performed.
- Certain flowers are thought to act as yorishiro for the souls of the dead. Remember how in PoFV errant human souls caused the flowers to bloom?
- Kuda gitsune are a Nagano speciality (of course)
- There is a "heretical" wish-fullfilling Buddhist ritual that is known as Iizuna hou, or Iizuna rite that involves kitsune spirits. It seems to have evolved from Dakini rituals, as dakinis and kitsune became conflated at some point.

I'm only 50 pages in and while some of this stuff isn't new to me, it's filling some gaps and it's presented in a way that's interesting and easy to digest.

I also found it interesting how the author compares Japanese mythology to a mycelium network of symbols, and how many myths kind of point to singular entities or ideas behind them, even if there are lots of local variations in the mythology surrounding them.