Possession is not a crime, it's distribution or public display.
Most censorship is done in post production, namely real life pornography. If possession were a crime, all of the porn studios would be constantly raided by the police looking for the raw video or pictures.
Game developers are the same way, most artwork is censored using post production software.
I'm sorry if it's a strange sentence in machine translation.
You're right, distribution and publication are crimes. But in addition to that, possession for sale is also a crime.
So why is the porn video industry not a crime?
1. Uncensored films (original films) are not intended for sale and are allowed to be possessed.
2. It is "acting" that looks like sex.
3. The film to be sold has a mosaic correction applied.
Therefore, it does not violate the law.
The porn video industry's excuse is that they're just acting as an actor and an actress in this video.
It's funny, but we don't sell porn videos in Japan. They are all "adult" videos.
Originally, commercial adult games are self-regulation. However, it actually needs to be reviewed by the "Ethics Organization of Computer Software" (EOCS). This is because it is necessary to have a third party review that it is not obscene. If you do not pass this examination, the number of stores that can sell your products will be very small.
After passing this screening, the EOCS "R-18 seal" can be affixed to the package. Games with this sticker are proof that they do not fall under obscenity. Therefore, even if you put it in the shop, it will not be subject to the criminal law.
Therefore, most commercial adult games are subject to a certain level of mosaic censorship.
Games created by individuals or circles are not (usually) reviewed by the Ethics Organization of Computer Software.
Send a copy to the place of sale and have them check it.
Therefore, DLSite and FANZA, which are major Japanese sales companies, have different criteria for passing the examination.
DLSite and FANZA will independently determine which levels are not treated as "obscene".
This is the reason why DLSite and FANZA have different degrees of mosaic. (DLSite has a slightly thinner mosaic)