The compilation of history books was continued for a national project of Japan over the period ranging from the Asuka period to the early Heian period; six history books were produced, which are called Rikkokushi.
日本国における国家事業としての史書の編纂は飛鳥時代から平安時代前期にかけて行われ、6つの史書が残されたため、これを六国史と読んでいる。