In addition there's a lot of hentai where many wouldn't think twice about the risk of someone being underage but looking more carefully at it one could make a fairly convincing argument someone is under 18.
A Swedish case had the entire court room laughing when the prosecutor claimed a manga character giving a blowjob was obviously underage because of the undeveloped boobs when it was actually gay porn.
I don't feel any attraction to underage women and have never to my knowledge seen actual child porn on the net (Samantha Fox's boobs and Scorpion's Virgin Killer album don't count) but fapping to completely normal manga could technically land me in jail. That's fucking scary. I'll have to fap to non-normal manga for now.