The Kaimei has a natural bristle brush-- weasel hair I do believe. A dandy little item, but rather pricey. That said, I've never had much complaint to make about the synthetic bristles of the Pentel Colorbrush-- if the Pocketbrush has the same kind of head it's a nifty tool.
There's a reason all those old school cartoonists ink with a brush and black India ...