I see hentai being a hot button issue. Since the vast majority of anime girls are canonically under 18 and even ones without strict ages (for originally drawn content) often obviously look underage or have features which make them look underage. (smooth faces with big eyes, flat chests, short stature.) And let’s not forget the large portion of anime characters which are basically designed to look as underaged as possible, but with unrealistically large breasts glued on to say “oh look they’re clearly over 18.”. How will this sort of content be handled? I know you say “you’ll know it when you see it.” but what about cases like these?

Consent would also be an issue in that a lot of porn stars have actively stated that certain scenes they have done were not at all consensual.