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Many theories have been thrown about but the most popular seems to be that connected to aryan origins in support of the nazi narrative.

Right @norbu . Maybe the Nazi war machine was already planning a way to incorporate the Japanese or Chinese into the German "family tree." I believe they ultimately did that with the Japanese in order to justify their alliance with them. Interesting stuff though!
full $teem ahead!

Just before the war the Nazis were intent upon finding exotic narratives which would give credence to their Aryan supremacy theory. One example was the swastika, a divine symbol of the Hindus used for thousands of years!

They could have warped logic with the Japanese to further their allaince and it seems very plausible when you consider such mission, who's goals were not entirely clear.