Conspiracy and Common Ancestry Theory in Japan

In 1992, Masami Uno, one of the most prolific anti-Semitic conspiracy theorists in Japan, who has claimed, among other things, that the United States is run by a Jewish “shadow government” and that the Jews are out to destroy Japan, published a book (Kodai Nihon no kokuin [The Seal of Ancient Japan]) claiming that the Japanese and the Jews are in fact related peoples. In recent years, Uno and other conspiracy theorists have blamed Jews for everything from genocide in Rwanda to the 1995 earthquake that decimated the Japanese port city of Kobe, but the idea of Japanese-Jewish common ancestry seems an ill fit with these ideas. How can it be explained?