The story seems to be set in a dystopic future Japan, where there exist two headbands. Whoever has the number one headband lives the life of a god on a far away mountain and only the person who possesses the number two headn=band has the right to challange him - this means that everyone wants to be number two. That honor however blongs to the Afro Samurai a man who's father used to be Number one but was defeated by the Number Two. Now Afro travels Japan wearing the Number Two headband searching for the Number one in order to take his revenge.
This is a surprisingly interesting plot with a lot ethical issues about friendship, revenge and the future beatifully interplayed with some of the best choreographed fight sequences I have seen in some time. It also features some excellent voice work from Ron Pearlman and Samuel L. Jackson.
All in all I can't wait for the second series - Afro Samurai: Resurrection.