By the middle of the fifth century, there had been a system in which a minor chief who was based in a part of the Boso Peninsula served a king of Wa in the Kinai District as a warrior, and the chief was granted an inscribed iron sword inlaid with silver due to his achievements.
五世紀中葉に房総半島の一角に本拠をもつ小首長が畿内の倭王のもとに武人として奉仕し、その功績によって銀象嵌の銘文をもつ鉄剣を下賜されるという関係が成立していた。