It is legal if content depicts images of adults having sex. Big tits, curves etc. When you get into small characters and flat chests I would ban that or not work with it.
I have been told by lawyers and content owners if you apply 2257 rules to it you should be okay.
That is if you follow 2257. If you are US based or hosted in US. Follow those guidelines in what you promote. People have been prosecuted in US for posting,sharing,trading content depicting illegal acts or non 2257 compliant acts in hentai.
Just my
