They have these ridiculous law that you cannot show genitals, not even in porn. So you cannot buy uncensored DVDs in Japan.
But the japanese porn makers aren't stupid, so nowadays they produce in Japan, but take a server in the US or wherever, just outside Japan. It's still not "legal" to view the stuff in Japan, but as no one can control it, it gradually changes.
Nowadays "censored" dvds are with very fine mosaic, almost invisible.
They can't even show it in Hentai porn, sucks to see a blank spot where the genital ar suppose to be, or they blurr it with speed lines.