五ヶ瀬川・大瀬川以南のこの地域に土持氏領が拡大するのは、建武(日本)3年（1336年）に土持栄宣が縣荘の半分職を獲得（「田部氏系図」）して以降と考えられるから、土持氏がこの城に居城するのは14世紀前半の半ば以降と考えるのが妥当であろう。

As it is believed that Tsuchimochi clan's expansion of territory into this region south of the Gokase-gawa River and the Ose-gawa River came with acquisition of half of Agata no sho by Hidenobu (栄宣) TSUCHIMOCHI in 1336 ('Tanabe clan Tree'), it is therefore reasonable to consider that Tsuchimochi clan occupied the castle some time after the first quarter of the 14th century. - Wikipedia日英京都関連文書対訳コーパス

しかし、12世紀末-13世紀初頭にかけて、この地域（三須・三輪・恒富地区＝宇佐宮領縣荘および島津領寄郡新名荘）を領有していたのは、門川伊東氏（＝縣荘）および源頼朝側近にして鎮西奉行・豊後守護の中原親能（＝新名荘）であり、延岡（当時は縣延岡）地域における土持氏領は五ヶ瀬川以北の宇佐宮領岡富荘に限られている（『建久図田帳』）ことから、12-13世紀、敵対勢力地のこの城を縣土持氏が領有しているとは考え難い。

However, it is difficult to believe that Tsuchimochi clan occupied this castle in this region of warring factions around the 12th to 13th centuries as between the end of the 12th century and the beginning of the 13th century this area (Misu, Miwa, Tsunetomi districts; these were formerly known as Agata no sho (manor) occupied by Usamiya and Niina no sho (manor) of Yose Gori occupied by Shimazu) was occupied by Kadokawa Ito clan (in Agata no sho) and Chikayoshi NAKAHARA (in Niina no sho) who held the position of Chinzei Bugyo (Defense Commissioner of the West) and Bungo Shugo (the Governor of Bungo Province) as well as a close retainer of MINAMOTO no Yoritomo; and the area in Nobeoka (then Agata-Nobeoka) occupied by Tsuchimochi clan was limited to Okatomi no sho (manor) in Usamiya, north of the Gokase-gawa River ("Kenkyuzudencho" (cadaster of domains, established by the order of Kamakura bakufu (Japanese feudal government headed by a shogun)). - Wikipedia日英京都関連文書対訳コーパス