This article is a review of Kikuchi-Castle and the ancient fortresses in western Japan. The ancient fortresses of western Japan have 12 castles recorded in history books and 16 castles not recorded in history books, totaling 28 castles. Especially, the Baekje Buddha statue excavated from Kikuchi-Castle in Kumamoto is a relic that supports the records of ‘Nihon-Shoki' that is said to have been under the guidance of Baekje's exile officials. In addition, the antefix at the edge of eaves excavated from Kikuchi-Castle is also thought to be a roof tile of Goguryeo Baekje's affiliation. As such, Kikuchi-Castle, which is related to Baekje, was built with the most advanced technology on the Korean Peninsula under the leadership of Baekje's exile officials, as was Ono-Castle and Kii-Castle. And Kikuchi-Castle has since survived for a long period of time in the third century, as the character of the Castle changed by the central government's initiatives.