Yeah, dunno about therapy, but some of the Graphic Adult Novels, are not “mere” comic books. From what I understand, it is not unusual for adults to read Manga in Japan, and some of the themes are disturbing and not intended for children.
Someone goofed in purchasing and classification.
Very common and much of the material is (within the rather odd, to most westerners, Japanese standards for what is considered "obscene") very violent and sexually oriented. While the text is in Japanese the art work tends to be very stylistic and I think that's what makes it attractive to western teenagers. But I would tend to agree that this kid (and/or his mommy) must have some preexisting "issues".
Maybe the kid went to the wrong section of the library?