I'll never understand the black bars thing on genitals.
I'm starting to think it evolved from censorship to a kink in itself and some people wouldn't be happy if it wasn't there.
Censorship is kinda weird in doujins. In anime and rl porn, it's simple, you just use the ol' mosaic, but in print it's all over the spectrum, ranging from the tiniest of strips to total whiteouts.