My friend is currently facing a court case for exactly that. The law was introduced in 2010 and since then basically anyone interested in manga risks running into things that the government has decided is child porn.

It’s like they made stepping in dog shit illegal; they can say that, but it’s not like everyone is going out of their way to step in something that’s everywhere… it just happens now and then.

EDIT: Also, notably it specifies later on that it includes the depiction of ‘imaginary’ children.