Japan is the wrong country to use as an example, bruh.
Besides, there has been virtually no cultural integration of white and Black in Africa. Whites who settled on the continent were pretty stringent about that whole apartheid thing, therefore their culture is still largely Dutch/German/British wherever you find them. They have largely made no effort to become a part of their new homes; they wanted to subjugate their former colonies and re-shape their homelands on African soil.
I don't think you can call them African, and I doubt if they would if they were being honest, either. But again, my first rule is self-determination. Call yourself what you will. Just know thyself.