Another opinion about the cause of his death is that he was involved in a political confrontation and assassinated as Motomasa was close to the side of the Southern Court (Japan) in his latter years because the power of the Southern Court was strong at both of the aforementioned places, Tenkawa Shrine and Ise at the time.
死因については、前述の天河社、また伊勢はともに当時南朝(日本)の勢力が強かった地であったことから、晩年の彼が南朝側に近かったとし、その結果政治的対立に巻き込まれて暗殺されたとする説もある。