In this picture the Sun Goddess, Amaterasu Ōmikami, is emerging from a cave, where she had been hiding, thus obstructing daylight. Outside the cave other deities were dancing and causing turmoil trying to tempt her to step out and make the world bright again.
This scene is one of the highlights of the stories told in Kojiki, 古事記, ”Records of Ancient Matters” (712) and Nihonshoki, 日本書紀, ”The Chronicles of Japan” (720) about the mythological past of Japan. These chronicles were compiled on imperial order and their purpose was to consolidate the newly established Yamato state and legitimize the power of the emperor as a descendant from heaven. They both tell more or less the same story, moving from mythology to history. Nihonshoki is written in classical Chinese and, being more elaborate and detailed, it is more reliable as a historical source. Kojiki, again, can be said to represent the oldest piece of Japanese literature, because in it Chinese characters are partly used phonetically.
Back to the Sun Goddess. Where did she come from? Literally, she was born from the left eye of his father, a deity called Izanagi. Also several other deities were born in connection of various activities of Izanagi and his spouse Izanami. They were the couple who first started to inhabit the Japanese islands with their offspring, after having created the islands first. They themselves had been born spontaneously from the primordial universal chaos.
Deities, that came to be born in myriads, were, and are, called kami. Kami are everywhere, the whole nature is sentient in Japanese view and experience. Later the kami world view became to be thought as a religion and was called shintō, the way of kami, to distinguish it from Buddhism, the way of Buddha. Both religions have lived in Japan next to each other until the present day.
Amaterasu was the ruler of heaven but her grandson descended on earth and became the grandfather of the first Emperor of Japan called Jinmu. Jinmu became the ruler 11.2.660 BCE. The date of course is mythological, but still today, the line of emperors is counted down from Jinmu, so that the present Emperor is 126th in order and the present year is Reiwa 令和 3. Reiwa means ”beautiful harmony” and is the name of the era that started 2019 with the change of the Emperor.
So the emperors of Japan are descendants of a goddess. But not only that, every Japanese man and woman is said to descend from the kami world. This has been the basis of the unity and uniqueness of Japan. But alas! In the end of the WW II the occupier demanded the Emperor to deny his divine origin. This was important for foreigners. The myth of Japanese origin however survived. The Japanese still may have their kami whispering to them that nothing in Japan would really change.
Neither of the chronicles have been translated into Finnish, but English translations are available.