Konnichiwa Maciamo-san!

Do you really think the average Japanese have any knowledge of what you've been talking about?
Of course! most of all Japanese have not any knowledge!

You want to know about Japanese family name. I think that you have a lot of question. Of course I can reply only "It is a custom!". But you can not learn anything from it. And I tryed to explain from Japanese folklore.

NANGI