The first theory claims that it is still placed in the Ise Kotai-Jingu Shrine, while a second theory argues that the mirror placed in the Naishidokoro (Kashidokoro) (the Three Shrines in the Imperial Court) was sunk offshore in the battle of Dannoura (the final battle of the Heike-Genji wars) with Emperor Antoku at the defeat of the Taira clan but later collected along with the Yasakani no magatama (comma-shape jewel [another of the Three Imperial Regalia]) by MINAMOTO no Yoshitsune, and then another theory describes that the mirror was moved to another place before the defeat of the Taira clan.
伊勢神宮の皇大神宮に変わらず安置されているとする説、宮中の内侍所（宮中三殿）にあったものが、平家滅亡の際、安徳天皇とともにひとたび壇ノ浦に沈んだものを源義経が八尺瓊勾玉とともに回収したとする説、平家滅亡前に他方へ遷したとする説などがある。