Depends on where you live. Not legal in the UK for example. In the US it can even be broken down at the state level, although there’s lots of debate on whether states are able to enforce their laws. “Obscene” speech is not protected under free speech, the argument would be whether or not the naked drawings had artistic merit or not.

I’m not a lawyer, but I do know that people in the US have gone to prison for possessing naked images of fictional children and it’s on the books as illegal in many other countries.