I don't really know what happened to them, so this is all just my speculation:
The Heydouga 4017 / Shirohame EMS series at heydouga.com stopped shortly after Japanese cops started investigations on some big name producers of uncensored porn. For example, Tokyo Hot got shut down (at least no more new content from them) because of some sorts of illegal activities going on. My guess is that Heydouga wanted to stay out of any trouble and decided to precautionarily delete their uncensored gangbang type of videos (they kept older ones like Night24 though).
Anyways, Shirohame seems to still exist, they release videos regularly, I don't know if it's really new content or if it's as good as it used to be, but you can find them at
siro-hame.net
