Perhaps some of the only porn someone can consume ethically. I guess there's an argument to be made about poorly paid animators drawing smut in animation workhouses, but it feels like most of the western world, when it comes to hentai, consumes rule 34 of franchise characters from media. Beat my brain up as I may, I can't see anything wrong in that and would much rather a fictional character be debased than an actual human for money.
I mean, I'm sure there are people who go into porn (or open an OnlyFans, etc) fully consensually and without coersion. But in terms of a random drawing of pornographic content, you will have much better luck choosing something ethical if you go with hentai.