The "butterfly" has to do with the silk worm business. The old nobles among the Yayoi and the pre-Samurai Ainu used this symbol. More recently several branches of the Royal Family have used one butterfly, or two butterflies (head to head). I have seen three butterflies, which are similar to the Mon that would use three balls of silk thread.
The silk worm business, interestingly enough, was once tied in directly with traders who worked a route that ended in Japan and stretched all the way to Rome (which is why it was called the "Silk Road").
There is some evidence that European-like people actually operated silk thread collection posts in Japan itself. This is inconclusive because I don't think they've found any Caucasion skeletons in Japan from that period.
Yup. There even was a pre-'Silk Road' road through the whole region. Just this morning, Western Han graves have been discovered near the Three-Gorges-Dam area. It wouldn't suprise me if some Caucasian skeletons were found in this grave yard.
"I don't think they've found any Caucasion skeletons in Japan from that period."
The oldest Jomon skeleton ever found in Japan is 13k years old. Then there are the Hakka...