The Kojiki or Furukotofumi (The Records of Ancient Matters), is the oldest surviving book in Japan. While written in Chinese, the book concerns the deities of Japan. It is one of the primary sources for Shinto, the national religion of Japan.
The Kojiki was presented by Ō no Yasumaro to the Emperor Temmu in 680,  and is based upon an earlier text called  the Kujiki, which is lost, and stories which had been passed down over generations. While some of the stories resemble similar stories from China most scholars believe the stories are specifically Japanese.
Little is known of Yasumaro save for the dedication in text where he describes himself as an Officer of the Upper Division of the Fifth Rank and of the Fifth Order of Merit.

The Kojiki

The Kojiki details the creation of the Kami (deities), their siblings, and the earth itself and tells a largely mythological history of Japan’s early Emperors. It differs from the The Nihon Shoki, which also recounts the history of deities, but is mainly concerned with real historical events.
The text relates the story of the original kami, who were created in the beginning upon the plane of high heaven. The creation story was told in the lost Kujiki.
The Kojiki contains various songs/poems. While the historical records and myths were written in a form of Chinese with a heavy mixture of Japanese elements, the songs are written with Chinese characters used to convey sounds only.
The Kojiki is divided into three parts: Kamitsumaki, Nakatsumaki, and Shimotsumaki.
The Kamitsumaki includes the preface and focuses on the deities of creation and the births of various deities.
The Nakatsumaki begins with the story of Emperor Jimmu, the first Emperor, and his conquest of Japan, and ends with the 15th Emperor, Emperor Ōjin. The stories are mythological.
The Shimotsumaki covers the 16th to 33rd Emperors, but has very limited references to the interactions with deities which is in marked contrast to the first and second volumes. Information on the 24th to 33rd Emperors is largely missing.