The precise site of Hirotsune Kazusa's castle remains unknown; however, exploration of castle sites built during the medieval period has been conducted in recent years around Ohara-machi Town, Isumi-gun County, Chiba Prefecture (presently known as Isumi City) and Onjuku-machi Town and progress was made in identification of the site.
上総広常の館跡の正確な位置は今もって不明だが、近年、千葉県夷隅郡大原町(千葉県)（現いすみ市）や御宿町一帯で中世城館址の調査が行なわれ、検討が進められた。