This theory is to identify Toyo as Yorozuhatatoyoakitu-hime, because she was the person who was a very close relative of Amaterasu and had the character of 'Toyo' in her name; this was the argument Biten YASUMOTO wrote in his "The mystery of Himiko; New Edition"(Kodansha new book).
アマテラスの極めて近い親族で名前の中に「トヨ」の文字がある彼女を臺與に比定する説で、安本美典が『新版・卑弥呼の謎』（講談社現代新書）で述べている。