The issue isn’t really even that. If the age of consent were to be raised to 16 of 18 or whatever, there would still be no law preventing people from drawing underage anime characters in sexual positions because Japanese law and police view child pornography as pornography made with a child, not pornography depicting a child.

An imperfect analogy is that murder is already illegal, but nobody gets arrested for drawing a Manga where one character murders another. No real person has been harmed and therefore there has been no crime.

I’m not saying I support this, but that’s how it apparently is.

Japan’s national age of consent is 13, but every single city/prefecture/organizational whatsit has laws effectively raising it to 18.