Possessing child pornography isn't a crime here? What? No, I'm pretty sure that still is (in fact, I'm certain that still is), so the crimes are possession, production, and distribution.
On Burst Angel: Yeah, that's the one. Anyways, the flat chested one was sexualized. The swim suit is not anything special, but she's still sexualized. The kid, maybe not so much, but the whole tone of the show is sexualization, and she's in the show. If you have a porn with a 10 year old fully clothed just watching in the corner, that's STILL A BAD THING.
On Negima: the first two books are essentially porn excepting the first chapter and the last chapter of the second book. Everything else is gratuitous, but not quite porn. Yeah, that's right, I said it.
On the definition: that's not the definition I've heard before. Although the definition varies from person to person, the one I've always heard was that porn has an intent behind it that erotic art lacks. The definition is still nebulous enough to be open to interpretation, and porn for one might not be porn for all (for an example, look up "inflation" videos on YouTube. People in inflating latex suits. Yeah, fetishes are weird.)