Personally, I disagree. Chrone has her own personality, she's not there "just to be black". I'm also not sure why her design is considered offensive, it perfectly fits her image as a threat to the characters that is also physical, and enhances the fact they're kids fighting a world of adults. Drawing her according to the manga "norm" would certainly have been considered a form of whitewashing too ("They made her black, but she had to look white except for her skin to be accepted").

Then, as for the fact that everyone else is moe etc., how come it is conveniently forgotten that Phil is not a Caucasian/Asian pretty little kid, yet he's easily one of the most intriguing and important characters in the recent chapters? Just look at the community, he's become extremely popular.

Not to mention that acribing to Japan the exact same historical sin as the US and some European countries (slave trade, racism), is naive. Japan can be racist, but there's no reason why mangake (or anyone else, really) should go through immense lengths to prove that some of the interpretations that can be attributed to them are wrong. They don't have to apologize for something they haven't done, and the sheer power of Sister Chrone has a character easily trumps any suspicion of racism.

The downvote of the first comment is not surprising (though not necessarily justified), s/he just said her design is offensive - which sounds like bait - and only afterwards explained why.