Tell me the history of Japan.

The origin of Japan is about 1 century, and there are more than 100 small countries in Japan (some of which established diplomatic relations with the Eastern Han Dynasty). Later, these small countries gradually unified. In the 4th century A.D., relatively large countries were established in Kansai, and it is said that the ancestors of today's royal family finally unified these countries. At that time, Japan included western Honshu, northern Kyushu and Shikoku. Therefore, it will take a long time for this country to be unified. Therefore, it is difficult to make an accurate judgment on the exact date of the birth of Japan. According to Records of Historical Records and Records of Japan, the first emperor Emperor Jimmu was founded in 660 BC and acceded to the throne. The date of his accession to the throne is equivalent to 1 1 in the current Gregorian calendar, so this day is designated as the "founding day".