The Bitchu theory comes from the "Imagawa-ki "and "Taikoki," when Shun FUJII, who had researched the old documents at Hosen-ji Temple in Ihara City, published a paper in 1956 stating that Soun had been the Shinkuro Moritoki ISE who was an attendant to Shogun Yoshinao ASHIKAGA.
備中説は『今川記』および『太閤記』に書かれており、井原市法泉寺の古文書を調査した藤井駿が1956年に早雲を備中伊勢氏で将軍足利義尚の側近であった「伊勢新九郎盛時」とする論文を発表した。