Should my friend be worried?

well, one of my close guy friends got curious about and ended up looking at something called hentai. He said it was some sort of graphic Japanese . He told me that this happened like 7 or 8 months ago, but he said there might have been a few of these hentai comics, or whatever you want to call them, that involved children under 18. hopefully most of you know what I mean. So to recap: now he is freaking out over something that happened over half a year ago (btw he said that he was disgusted with it), so i am asking on his behalf, Should he be stressing out over this? I'd really like to help him get over this.