Shintoism is the Japanese traditional religion, but its origins are rooted back in ancient (even prehistoric) times, when Japan does not exist yet. That’s why there is no known historical founder of Shintoism. It’s known that it became named Shintoism centuries after it started, as a way to separate it from other religious practices as Buddhism.
Perhaps, it is its association as main character of the Japanese culture that led Shintoism (and its rituals and main beliefs) to survive healthy through centuries without a founder, a date of creation, a definite sacred text or a set of homogeneous beliefs.
In Japan, it is accepted that Shinto preceded the Japanese people and culture. Some trace its origins in the Yayoi culture developed in Kyushu Island that built Shintoism back in the 3rd century B.C. around Shamanism practices opposed to Buddhism.
While there’s not a sacred text, Shintoists use books related to its history and lore. Together, those provide them a full background of stories and beliefs, such as Kojiki (a record of ancient matters that explains Shinto history), Rikkokushi (a series of national chronicles of Japan), Jinno Shotoki (an extended study of Shinto, policy and history of Japan)…
Some of them are compilations of oral traditions written back in the Middle Ages, or even in ancient ages, that serve as a basis to explain Japan’s history. For instance, in the Kojiki, it is said (written) that the Japanese culture is strongly rooted to the origins of the imperial family, descendants of the sun goddess Amaterasu Omikami, which is also one of the main Shinto deities.
Nowadays, Shintoism religion is practiced by 119 million people and most Japanese usually combine it with Buddhist religion, assuming both as practical beliefs to face different aspects of life as birth or death. Shintoism influences not only religious practices or beliefs, but also is linked to ikebana’s flower arranging, architecture and design, sumo wrestling, arts…