My great-grandfather was a Japanese soldier during WWII?

Question:

First thing is first, I am Filipino. My mother told me we are part Japanese? As far as SHE knows, my GREAT-grandfather (her GRANDFATHER) was Japanese and stationed in the Philippines as a soldier for WWII. I know I am 1/8th Japanese (Grandmother = 1/2, Mother = 1/4).

In that case, how can I make sure I am part Japanese? Do I take a DNA test or would the Japanese embassy have to check it out for me? Where can I look to be sure?

Answer:

What do you mean by make sure? I don't think there is any certificate or something to prove that you are 1/8 Japanese.