I have just published a new book on Amazon, Myths from Prayers and Poems. This is a compilation of three of my Patreon essays, covering the myths of the kami that are found in the norito prayers in the tenth-century Engishiki, and those that are found in the poems in the eighth-century Man’yōshū.
There is less in these sources than one might expect. Most of the norito do not retell myths, and the kami are not a substantial presence in the Man’yōshū poems. That is interesting in itself, of course, because it shows what people at the time wanted to write about.
The fragments that we do get are also interesting, because they are almost always different from the stories we have in other sources. Sometimes, they are obviously versions of the same story, but are critically different. There are a number of cases like that in the Nihoshoki, and now we have even more. There is a version of the descent from the heavens that changes the role of one kami from betraying the kami of the heavens to working loyally for them — and it may be significant that this is in a prayer recited by people who claimed descent from that kami.
Some of these myths tell us about kami who are not mentioned elsewhere, while others, as mentioned above, give us very different versions of kami we thought we knew. I think they are a valuable, and interesting, perspective on early Shinto beliefs.