you are missing an option. When i read manga I never think about what race the characters are, unless they go out of their way to specify. Even then I don't think about it beyond the pages when it is referenced. Saying I "consider" them any race would just be false.
When I think about it, I tend to see often see characters as white. Sure they may be in Japan, but having big blue eyes and brown/blond hair doesn't make someone look Asian to me. It definitely depends on the art style too. Probably the fact that where I live, most of the people I see are white doesn't help either.
On a different note, I find it amusing that in a given series Chinese people look perfectly Asian, black hair, brown/black small eyes but Japanese people don't.