I would very much like to double down on my recommendation of The Catalpa Bow. It's excelent stuff and puts a lot of context into many aspects of Japanese culture and mythology.

Some stuff off the top of my head:
- Ascetic practices and cold exposure repeatedly play a big role in Japanese shamanic practices. Training for itako, blind seer women, included up to 33 333 buckets of cold water poured on them over the course of their training.
- A kind of cultivation or activation of "inner fire" seems to be a prerequisitive for shamanic success, and the fasting and cold exposure seem to be a way to force this out. Some aspects of this veer close to Indian ideas about kundalini.
- Some Buddhist temples were built in places that were thought to be or at least represent locations in afterlife, and many have a bridge over an artificial dry riverbed. That's the children's hell also featured in Wily Beast.
- Many people ending in shamanic roles had a history of sickness and neurosis that became resolved once they went through some kind of initiation.
- People took their reimu (dreams featuring deities) extremely seriously, and people who didn't heed the call became ill or started to go insane. Following the call resolved these issues.Some of the descriptions of the dreams are uncannily close to some of my own, including the type of voice the deities speak with and how they choose to appear.
- Some kind of wreath or halo of flames is not only associated with the luminous kings of Buddhism, but also with gongen, these manifestations of enlightened beings appearing as local, often very wrathful beings. Recall the fire surrounding a lot of later depictions of kami in Touhou.
- Tengu were at times seen as enemies of not only Buddhism, but also protective deities, because often the protective deities manifested as snakes. Birds and snakes were seen as kind of enemies. Maybe the Moriya-Tengu feud has a deeper mythopoetic meaning to it.
- Tenguphiles rejoice: some of the boys they would abduct and drive insane would return with shamanic gifts.
- The author met a mountain ascetic woman who had tengu-like traits, a "birdlike" face, glinting eyes and ability to move very fast in difficult terrain. Very odd anecdote, the only of it's kind so far in an otherwise very academic text.
>>49816289
Snakes and dragons are extremely common elements in many mythologies. Their roles tend to be very diverse though. I've been still reading The Catalpa Bow, and even in that book, even in the context of shamanic practices of a single culture, snakes keep cropping up. Sometimes in very positive light - they are associated with fertility, act as spirit guides and protect. But there is also a more troublesome side to them too, even wrathful. They are associated with things that snakes aren't really associated with in real life, such as fire. The author herself notes that some elements surrounding these fiery snakes veers close to Indian ideas about kundalini. Perhaps fragments of it got transmitted to Japan via Buddhist influence, perhaps it's convergence.

I think there is 100% more to it. I think the way they shed their skin and are "reborn" is a big part of it, but there is something beyond it. It's something extremely primordial, likely pre-human.

Rainbows are fascinating because they reveal something that is normally hidden, the spectrum of colors hiding inside undivided sunlight. There's a lot of stuff in certain forms of Buddhism about rainbow lights and rainbow bodies and how inside everything that seems substantial is just this rainbow hued light. It's strangely modern - everything really is energy at different frequences, and visible light is just a vsible manifestation of this.

When it comes to native Japanese myths, I believe the Floating Bridge of Heavens that the heavenly kami is often thought to be a rainbow. I believe the gods of Norse mythology also used a kind of rainbow bridge too?
>>49816319
They are archived here.
https://archive-of-the-sealed-gods.neocities.org/site-functions/acknowledgements