Amazonman (アマゾンマン) was a competitor in the 20th Chojin Olympics. He was eliminated in the battle royal. Originally portrayed with a bone through his nose, this depiction was deemed a politically incorrect depiction of indigenous people and has been changed in recent printings. The Japanese media has become more sensitive in regards to racism, and especially about depictions of indigenous peoples, after late-eighties controversy over the Fujiko F. Fujio manga and anime Jungle Kurobē.

I think this is due to the influence of the American media in Japan, especially before the 1960s, which was very racist towards minorities. I think the more recent reprints of Ozamu Tezuka's manga usually have a page explaining this, especially the older ones. It's kind of ironic that Astroboy has blackface when part of the manga talks about how bad racism is.