Why aren't there many black people depicted in manga or anime?
There are black people in Japanese animation and Japanese comics, but not many, and how they are represented varies wildly by artist and by era. The same can be said of people of non-Japanese cultures. Just as the civil rights movement altered American culture, Japanese pop culture has been changing, and just as attitudes differ person by person in the U.S., the same is true in Japan.
In this page I will try to be forthright in the hopes of encouraging understanding.
So, why are there so few black people?
One simplistic answer is a combination of (1) Japan is an Asian country with a long history of homogeneity and, even now, very few racial or ethnic minorities (walk down the streets, and it's almost all Japanese, once in a while a white tourist or businessperson, and that's about it!) (2) the world's most popular marketed culture is apparently American entertainment, and the mostly white nations have most of the world's power (a recent Boston magazine lamented the spread of Western pop culture to Fiji, where people promptly began dieting and trying to look like those models). Given all this, Japanese popular media will, I believe, tend to fixate on both things familiar (Japanese) and things highly popular by worldly standards (white Western/American).
In an island nation historically physically separated from other cultures, from where will that nation get its images of other people?
Hundreds of years ago, Japan imported a lot of Chinese culture, perhaps akin to the way the West imported a lot of Greco-Roman influences. Scholars braved extremely dangerous and lengthy journeys to go study in China and return. There seemed to be a lot of respect for Japan's big neighbor, though arguably the failure of Mongolian and Chinese forces to successfully invade Japan in the 1200's gave Japan a little too much sense of divine protection. Also, in the colonial era, China became dominated by European countries who used drugs to enslave its people, and it is suggested that Japan lost a lot of respect for China at that time.
As for Japan and the West, Japan tried to cut itself off from Western influence for many years. All this changed when the U.S. decided it wanted to use Japan in the colonial power-grabbing going on around the world. Japan's trading borders were forced open in the 1800's by the U.S. government. (www.suite101.com has a brief overview of that period: Part I and Part II.)
Japan, seeing its own weakness, rushed to catch up with the Western colonial powers that then ruled the world -- a remarkable, painfully difficult process seemingly driven by desperation and determination. Japan started taking up many Western things: science, technology, fashion, military power, art, and the act of just plain overwhelming other societies and owning colonies. In the artistic sphere, it picked up some rather nasty Western racial stereotyping (going so far as to try to make itself look "white" and other Asians look stereotypically Asian in propaganda art!), and also seems to have picked up the stereotypical cartoon style of drawing black people from a then-rather racist West. (Perhaps the thought was similar to the attitude of playground kids who think if they join in and try to be like those picking on smaller kids, they will become more popular. See the ominous final quote on this page.) But despite Japan's efforts to be just like the Western powers, there is a strong sense that it still was not treated with equal respect -- perhaps for racial and ethnic reasons! In fact, I have lately heard that American diplomats would use racial slurs in referring to the Japanese officials -- no WONDER Japan got pushed further and further away from the U.S., and more toward war. So, this sense of being unfairly treated would, it has been strongly argued, result in some of the events in the early-to-mid 20th century.
(Side note on propaganda: Consider that, during times of war or unrest, that "enemies" are often depicted and treated as strange, funny, weak, separate, different -- as one can see in WWII-era American war posters and cartoons, not just Japanese war propaganda art.)
It is not within the scope of this document to go into the actual horrors and warfare of the turbulent first half of the 20th century. Suffice it to say that, in post-war Japan, some of the old stereotypes and artistic styles continued to play a role into the 50s, 60s, and probably beyond, I think in large part due to the lack of a vocal minority population and lack of a big civil rights movement. More stereotypes from Western popular media (including action TV shows and sports like boxing) also seem to have filtered over into Japan. Ironically, at the same time, it seems that Japan also felt some of the sting of Western racism. Thus, I think you wind up getting a very mixed bag of ideas. A great example of the mixed bag of the 60s era is Cyborg 009, which had characters from around the world (including some frighteningly stereotypical European, American Indian, African, Chinese characters, etc.), in addition to what might be symptoms of self-esteem problems (e.g., how the main character was half-Japanese, half-Caucasian), and yet some real sensitivity to racial issues, the idea that every individual has something to contribute, the idea that human beings are really part of a family.
Thankfully, the last few decades have seen more and more positive changes in manga and anime. There is now a publisher's note at the end of some Tezuka Osamu manga, explaining and apologizing for the late mangaka's old, stylized way of drawing various types of people (as one of the earliest true mangaka, his style appears to have been influenced extensively by early American cartoons) -- as well as pointing out the author's dedication to teaching about compassion and the value of human life. A very recent shojo (girls') manga had a scene in an American house where white, black, and Asian people mingled at a party as equals -- and perhaps more importantly, it made no big deal of the scene.
Ironically, I think one of the things that has greatly helped is America's overall changing attitudes. Recall that most Japanese people have little direct exposure to many other cultures and races, but they do see a lot of American media-based culture (TV shows, movies, sports figures, products, news stories). Hence, surely what Japan sees stems in some part from what the powerful American media sees, even today. So, just as Western culture helped make racism into a powerful influence, Western culture can help (and is helping to) undo the damage. Not to say every nation shouldn't be responsible for itself, but to suggest that those with great power have both great responsibility and great opportunity.
The need for deep reflection is vital and urgent: just as American culture is influencing Japan and the world, Japanese culture is influencing America and the world, these days seemingly more than ever. (A coworker noted seeing a child in Moscow who was drinking Coke while sporting a "Dragonball Z" t-shirt.) With the Internet and TV spreading everywhere, the cycle of worldwide cultural exchange and influence can only accelerate.
But remember: individuals within any nation will still have their own opinions, whether bigoted or enlightened, apathetic or caring, wayward or upward. One of the problems we see with this issue is the hurtful nature of stereotypes... let us not be guilty of making the same judgments upon others or those of other nations. Let the cycle of arrogance and misunderstanding -- so sharply defined through all the millennia of warfare, in nations across the world -- stop now.