There are plenty of Black people in Anime and Manga.
You just haven't watched/read enough to come across them as of yet.
I've been viewing Japanese animation Media since 1995 officially and have seen tons.
They may be token amounts .... but that should be considered nothing short of amazing considering the amount of Black people (mostly Africans) in Japan barely number in the thousands.
The same goes for German and Scandinavian media. There are almost a negligible amount of Blacks (again mostly Africans) in these countries yet tokens always appear as newscasters and in TV shows.
Throughout my chronology of media I have actually seen a more disproportionate lack of representation of HISPANICS in Japanese media, considering that Peruvians/Brazilians make up a large foreign population numbering somewhere in the TENS OF THOUSANDS in Japan. Some of these persons hold bona fide permanent residency yet they never receive as much as a "shout-out" in the Japanese media compared to Blacks (mostly Jamaicans, other Carribean Blacks, Ghanaians and a very
very small amount of Afro-Americans)
The Michiko to Hatchin example is AN EXTREMELY RARE example that is directly due to the fact that this is the year 2009 already and the Japanese are realizing they need to expand their horizons (as if they didn't already know that since Commodre Perry came to Japan).
Brazil will be a key country in times to come and the immigration from Brazil will only increase, and many of these Brazilians have very ambiguous racial identities. I think it's represented well in Michiko to Hatchin as they show both light and dark-skinned people. Japan's artists have ALWAYS been diverse and open-minded as it's what earns them the most money internationally when their production is exported, but the domestic crowd's taste will always be prioritized.
At this rate I am starting to feel that the Japanese are having more passion regarding the rights and enfranchisement of the African-American community than America itself! Something is wrong here!!! LMAO
Regardless of what may be considered stereotypical depictions (such as that of Mr. Popo in DBZ) I think that given the appearance of the rest of the cast (Piccolo, Frieza, Buu and other species in the series) Mr. Popo really isn't the main oddity attraction. Some people see Mr. Popo as being an icon with racist connotations, while the same could be said about Goku's Super Saiyan transformation. Some have even asserted that Majin Buu is supposed to be Chinese, another bullshit theory (absurd right?). People will take anything out of context and warp it to their own weird imaginations.
Japan is not racist, it's merely xenophobic. It may have degrees of discrimination but the majority of stereotypes perpetuated in the society are solely for defensive purposes. There was only two administrations in Japanese history that were publicly accepted and who operated on notions of racial superiority. Compare that to several Russian Tsars, almost the entire history of the Prussian empire and South Asian kingdoms as well.
Anyways somewhat off tangent but overall....I think the Japanese have come a long way and are accepting their fate of becoming a "genuinely" multi-cultural society, and that cultural mixing can be a good, enriching thing.