I have just made two more of the Patreon essays available for purchase on Amazon. These essays, Myths of Jinmu Tennō, cover most of the myths about Jinmu Tennō, the first Tennō, from when he left Hyūga in southeastern Kyushu to the completion of his conquest of Yamato in central Japan. There are a few more myths about the establishment of his rule, and I will write another essay about those in the near future.
The scholarly consensus is that Jinmu Tennō did not exist, and that there was no figure who could be called a Tennō in Japan in 660 BCE, the traditional date of his accession. However, there is a good chance that the myths reflect something about the formation of the Yamato polity from the third to sixth centuries CE, and there are a number of accounts of Shinto rituals that can be taken to shed some light on early practices. (Just how early is, of course, up for discussion, but seventh century CE at the latest.) Similarly, there are a number of kami who appear in these myths, and their actions tell us something about early attitudes to the kami. They are useful evidence for the late prehistory of Japan, even if they are not history.