Oh, it’s a serious topic here. I got carried away. I should focus on something actually reasonable for once. Alright, where was I…
In Japan, there’s a law that prohibits showing genitalia uncensored. It’s not just a hentai law, it’s shared across the whole Japanese adult industry. If you watch anime you might have noticed that Japanese boys look silly when they see open genitalia, like it’s their first time seeing them. That’s because that’s pretty much might be their first time seeing them! So you can say that it’s shared not just across the adult industry, but across the whole modern Japanese culture as well.
In fact, there’s a hole in that law. Nothing stops a Japanese artist to put even a single pixel over their character’s genitalia and call it a day. But no one wants to take that extra risk and get sued for a drawn penis, nor would any Japanese-based image board accept such content. So, due to the lack of standardization, there are a million variations of censorship. Mosaic pixelization (usual for hentai), blurring, lines, fully white-colored penis, not showing genitalia at all, you name it.