Chikushikoku (竹斯国) is the name of a country or land that appears in the Book of Sui Dynasty and History of the Northern Dynasties in the history of China as being in the Japan region. or land name that appears in Northern History. It is compared to Tsukushi Province.[1]
The country of Chikushikoku appears in "Book of Sui" volume 81, biography 46 "Eastern Barbarians, the country of Buyeo" and "Northern History" volume 94, biography 82. It is mentioned immediately after the passage "The Emperor of the Land where the Sun Rises" in the letter sent by the Buyeo (Wa) envoy, Tarishihiko, to Emperor Yang of Sui.
『Book of Sui』In the next year, the king sent Pei Qing, a scholar, to the country of the night, and he went to the country of the south, to the country of Danla, through the country of Dusma, which was in the middle of the sea, and to the country of the east, and to the country of the east, and to the country of the king of the Qin, whose people were the same as those of China. They passed through more than ten countries and reached the coast. From Takeshi to the east, they are all subordinate to the Japanese.
『History of the Northern Dynasties』In the next year, the emperor sent Pei Shiqing to the Japanese state, and he sent him to the island of Takeshima, looking south at the country of Tama, through the country of Dusma, which was in the middle of the sea, and east to a country, and then to the country of Takeshima, and east to the country of Qinwang, where the people were the same as the Chinese, and they thought they were the barbarians, but they could not be understood. They passed through more than ten countries and reached the coast. From Takeshi to the east, they are all subordinate to the Japanese.
It describes the route taken by the envoys from the Sui Dynasty. The envoys went from Baekje to Takeshima (not an island that has been disputed by Japan and Korea since the late 20th century), Tsushima to Iki, and then arrived at "Takeshikoku. The area east of there is said to be the territory of Japan. The reason why "Sui Dynasty" refers to "Hye-qing" and "Northern History" refers to "Hye-se-qing" is that "Sui Dynasty" was Naming taboo.
The common theory is that the "其人・・・・・・不能明也" part of the above Chinese historical document is an explanation of the Shin'okoku, but the following theory exists.