I wonder if that's possible in Japan for a black person
Like all "migrant workers", they're considered low class and are treated that way, similar to how Turkish people are treated in Germany.
I assume the OP is actually referring to these returned second generation Japanese.
I'd think a formal or business casual attire, with proper grooming, is a rather international signal that you're vaguely alright in your ways.
Anything specific you reckon otherwise for?