This article aims to analyze an understanding on the concept of gods according to the history of religions from primitive to middle age in Japan. The concept of Japanese gods has unique characteristics by acceptance and assimilation, amalgamation　of Buddhas from ancient Korea in early history of Japan.
At first, when we analyze symbolic elements of Dogu (clay figure) and Myth of 5 grains in Kojiki (the oldest extant chronicle) which contain Japanese religions and their faith, we can understand that the gods in Jomon period are related with the power of birth that is to recognize the birth of life by overcoming the death as the power of gods, and people in Yayoi period accepts holy ministry of the religious priests to connect mankinds with gods by an ancient Japanese tomb of a circular shape with a rectangular frontage or a myth of decent of gods from old Korean influence to form and set up of tribal state and clan society.
Secondly, the syncretistic concept of gods is popularized to people by the Bonjisoojek theory that the Japanese Jingi gods (the god of heaven and earth) are secondary manifestations of certain Buddhas or Bodhisattvas after introduction to Buddhism in Nara period, and also Buddhism are syncretized with the movements of Yin and Yang, mountain deities, the vengeful spirits, to take Kaji (attaining union) with gods or Bodhisattvas.
Thirdly, when we generalize the process of the concept of Japanese gods and the discourses of Japanese scholars on Japanese gods, Japanese gods have polytheistic and syncretistic　concept. According to Mr. Motoori Norinaga, the Shinto scholar, Japanese Kami(gods) in ancient usage, is whatever seemed strikingly impressive, possessed the quality of excellence, or inspired a feeling of awe.
Meanwhile Prince Shotoku(574-622), the Buddhist scholar emphasized that all of humankind had the capacity to achieve enlightenment,　Mr. Honen, the Monk of Pure Land Buddhism urged the only one; calling on the name of Amida as the single-minded recitation of the Yembul (the phrase namu Amida Bul, meaning “Praise to Amida, the Buddha of Infinite Light and Light), so that Buddhism and Shinto tend towards a harmonious fusion.
In conclusion, because of syncretization　of Shinto gods and Buddha, Japanese religions can maintain the traditional polytheistic concept of gods in order to regard the Emperor as a sacred god under the nationalism.