Some clarifications:
1. There are many types of Manga, some are
listed here, and it has been around in one form or another since the mid 1870's.
2. The
Legal Age of Consent varies around the world, in Japan the Federal Law states it is 18 but Prefecture Law has it as 13.
3. The West still commercially makes and sell forms of porn video/comics that are banned in many places, some of these forms include "Actual Incest", "Simulated Incest", Bestiality, "Water Sports", "Simulated Rape" and "Cannibalism". (I won't including any links but just goggling the topics or the major Porn DVD brands will allow you to find them yourself.)