From the description in the 'Rikkokushi' (the Six National Histories), the materials of the ancient history, and from the unearthed Paekche-type roof tiles and so on, Kikuchi-jo Castle is thought to have been constructed under the guidance of noblemen exiled from Paekche, therefore a bronze standing statue of Bosatsu (Bodhisattva) which is presumed to have been carried in by Paekche noblemen was excavated from the ruins.
古代史の資料「六国史」の記述や百済系瓦の出土例などから、鞠智城は百済亡命貴族の指導で築城されたと考えられており、遺跡からは百済貴族が持ち込んだと推定される青銅製の菩薩立像も出土している。