(720 AD), considered by historians and archaeologists as the most complete extant historical record of ancient Japan, was written entirely in kanji.
Chinese characters first came to Japan on official seals, letters, swords, coins, mirrors, and other decorative items imported from China. The earliest known instance of such an import was the King of Na gold seal given by Emperor Guangwu of Han to a Yamato emissary in 57 AD. Chinese coins from the first century AD have been found in Yayoi period archaeological sites. However, the Japanese of that era probably had no comprehension of the script, and would remain illiterate until the fifth century AD. According to the Nihon Shoki and Kojiki, a semi-legendary scholar called Wani (王仁) was dispatched to Japan by the Kingdom of Baekje during the reign of Emperor Ōjin in the early fifth century, bringing with him knowledge of Confucianism and Chinese characters.
The earliest Japanese documents were probably written by bilingual Chinese or Korean officials employed at the Yamato court. For example, the diplomatic correspondence from King Bu of Wa to Emperor Shun of Liu Song in 478 has been praised for its skillful use of allusion. Later, groups of people called fuhito were organized under the monarch to read and write Classical Chinese. During the reign of Empress Suiko (593–628), the Yamato court began sending full-scale diplomatic missions to China, which resulted in a large increase in Chinese literacy at the Japanese court.
In ancient times paper was so rare that people stenciled kanji onto thin, rectangular strips of wood. These wooden boards were used for communication between government offices, tags for goods transported between various countries, and the practice of writing. The oldest written kanji in Japan discovered so far was written in ink on wood as a wooden strip dated to the 7th century. It is a record of trading for cloth and salt.Not now mentioned in source
The Japanese language had no written form at the time Chinese characters were introduced, and texts were written and read only in Chinese. Later, during the Heian period (794–1185), however, a system known as kanbun emerged, which involved using Chinese text with diacritical marks to allow Japanese speakers to restructure and read Chinese sentences, by changing word order and adding particles and verb endings, in accordance with the rules of Japanese grammar.
Chinese characters also came to be used to write Japanese words, resulting in the modern kana syllabaries. Around 650 AD, a writing system called man'yōgana (used in the ancient poetry anthology Man'yōshū) evolved that used a number of Chinese characters for their sound, rather than for their meaning. Man'yōgana written in cursive style evolved into hiragana, or onna-de, that is, "ladies' hand," a writing system that was accessible to women (who were denied higher education). Major works of Heian-era literature by women were written in hiragana. Katakana emerged via a parallel path: monastery students simplified man'yōgana to a single constituent element. Thus the two other writing systems, hiragana and katakana, referred to collectively as kana, are descended from kanji. In comparison to kana (仮名, "provisional character") kanji are also called mana (真名, "true name, true character").
In modern Japanese, kanji are used to write parts of the language (usually content words) such as nouns, adjective stems, and verb stems, while hiragana are used to write inflected verb and adjective endings and as phonetic complements to disambiguate readings (okurigana), particles, and miscellaneous words which have no kanji or whose kanji is considered obscure or too difficult to read or remember. Katakana are mostly used for representing onomatopoeia, non-Japanese loanwords (except those borrowed from ancient Chinese), the names of plants and animals (with exceptions), and for emphasis on certain words.