I get really fired up talking about this because it's a tangle of tech, culture, and law that changes depending on where your screen thinks you are.
At a high level, most countries treat sexually explicit material through a few overlapping lenses: obscenity/pornography rules, child protection laws, intellectual property, and lately specific statutes about deepfakes and nonconsensual imagery. In the United States you have federal statutes like the PROTECT Act that target sexual depictions of minors (including some computer-generated imagery that appears realistic), and then a patchwork of state laws that add bans or penalties for revenge porn, nonconsensual deepfakes, or nonconsensual explicit images. The conservative federal approach to images of minors means creators are safest when characters are unambiguously adult and not depicted in realistic photographic styles that could be confused with real people.
Japan has its own quirks: historically the industry relied on self-regulation and censorship rules (mosaic for genitalia in mainstream adult material) while laws on child sexual depiction have been strengthened in recent years. The government has moved to crack down more on explicit depictions of minors, and platforms often prohibit sexualized images of anyone who could reasonably appear underage. Several European countries — Germany and the UK among them — have strict prohibitions on child sexual imagery (and some include drawn/animated material), plus broad obscenity provisions and national classification systems that can ban or index material. Australia’s classification system will refuse classification for sexual content involving young-looking characters, making distribution and possession illegal in many cases.
Beyond national criminal law, platform terms of service and content-moderation rules (major social sites, image hosts, app stores) are decisive in practice: even where a depiction might be legal in a jurisdiction, distribution can be blocked or accounts suspended. Copyright and privacy laws also matter when AI-generated works are trained on copyrighted images or impersonate real people. My take? If you're making or sharing adult animated content generated by AI, make characters clearly adult, avoid photorealistic portrayals of real people without consent, and respect platform rules — the legal map is messy and enforcement moves fast, but clear boundaries and good platform hygiene keep you out of trouble. I find the whole clash between creative freedom and legal red lines endlessly fascinating.