I do not believe that these manga depictions of sex with minors have "serious literary, artistic, political, or scientific value". So, I do not believe that they constitute art and therefore it's OK for the government to intervene.
Neither do our comments. Should they be subject to government approval too?
They are not obscene.
We're getting somewhere. So why do obscene stuff should, in your opinion, be controlled by the government? I don't mean why it's distasteful or unhealthy or something like that, but what makes you want to cross the line from "not socially accepted" to "men with guns ruin your life"?