A lot of people here are saying this is a good thing due to manga child pornography having no good reason to exist.
A fictional representation of child pornography has no victims whatsoever, so it does no harm, and there is a market/audience for it, so it clearly does have a reason to exist.
You and I might find it repulsive, but things should not be outlawed simply because the majority cannot comprehend it. An act should only be outlawed if there is a victim. Otherwise we're talking about a thought crime.
The stigma for pedophilia is wildly out of control. "Pedophila" means a sexual attraction to children. There's nothing inherently evil about that. Nobody chooses who or what they are attracted to. It is acting upon those desires in a way that exploits or abuses children that is vile. There is a world of difference between the two, yet society in general refuses to acknowledge this. The fact that the word "pedophile" is automatically assumed to refer to somebody who actually abuses children (as opposed to somebody who merely has a sexual attraction to them) is proof of this.
For clarity, for the rest of my post, I'll be referring to people who are attracted to children as "pedophiles", and people who act on these urges as "child abusers".
There are many pedophiles who would never dream of acting upon their urges. Some are good people, some are in healthy relationships, and some have a good sense of right and wrong. They didn't choose what they're sexually attracted to. And for some, it's basically a fetish, but not an all-consuming one that they are incapable of controlling. Many people have some kind of fetish, but they don't lose control and start trying to rape others who align with said fetish. But because pedophiles are stigmatised to such an extreme extent, they are viewed as no different from child abusers, so they have to keep it a secret from everybody out of fear. Some may feel pangs of temptation, but they don't dare seek any kind of help/support/therapy, as to do so means being vilified, and potentially putting their lives in danger. This is dangerous, as this is what can potentially lead to escalation, as many do not get help they could benefit from if it *is* all-consuming for them.
Some people will argue that manga child pornography encourages real instances of child abuse, but I don't believe this at all, as that's like saying furries viewing furry porn will then go out and have sex with real animals.
I find the thought of manga child pornography, furry porn, and My Little Pony stuff all extremely discomforting, but I'm not so closed-minded as to call for a ban on any of it just because of that. There are some people out there who like them, nobody is being hurt, and there is zero evidence to suggest that it encourages any kind of "escalation".
If I'm mistaken, and evidence does exist, please feel free to point it out to me, and my entire stance here will change, but otherwise, this is a thought crime, and counterproductive, as this kind of thing leads to pedophiles supressing urges (rather than seeking help) that can later manifest in far worse ways.
(Christ, typing all of that on my phone was a pain)