In response, they built a huge network of shore fortifications throughout the rest of the 600s, often with the assistance of Baekje engineers, generals and artisans.

[4][5] Unaware of the outbreak of the Silla-Tang War (670–676), the Japanese would continue to build fortifications until 701, after finding out that Silla was no longer friendly with Tang.

Kiyama is located on Mount Shiroyama (elevation 462 meters), which is part of the Setonaikai National Park, and which straddles the border between Sakaide and Marugame in northern Kagawa Prefecture.

At present, a golf course (Takamatsu Country Club) occupies the site and the ruins, including the remnants of gates and stone walls are scattered around the grounds.

Its layout and design of walls place it as one of many similar fortifications extending across the northern part of Kyushu and in other locations along the coast of the Seto Inland Sea, including Einōsan Castle and Yashima, as well as Ki castle in Okayama Prefecture on the opposite bank of the Seto Inland Sea.