The word Shintō — the way of the kami — is itself a retrofit, coined using Chinese characters to distinguish the indigenous practice from Butsudō, the way of the Buddha, after Buddhism arrived in the sixth century. Before there was something to contrast with, it did not need a name. There is no founder, no revelation event, no creed, no membership and no conversion; the Kojiki and Nihon Shoki are court-commissioned chronicles, not scripture, and no priest will tell you that you must believe them. This makes the tradition genuinely difficult to classify, and the classification has had political consequences: the Meiji state declared shrine attendance non-religious precisely so it could be required of everyone, and the postwar constitution had to unpick that. Sociologically the practice is transmitted by household and locality rather than by teaching, which is why it survives at enormous scale in a country that reports very low religious belief.