As anime and manga are immensely popular forms of media, their subjects can sometimes be sensitive. One genre that addresses such sensitive material is called hentai (sexually explicit anime). This subset of titles typically features abnormal sexual practices like tentacle erotica or incest as part of its plot line. These stories typically feature an innocent main character who must confront his or her taboos; these types of releases appeal particularly strongly to Japanese animation enthusiasts called otaku who enjoy watching animation-based material such as comic books.
Most workers in the hentai industry don't have much say over which projects they take part in; often times their contracts dictate which projects they work on; but freelancers who often collaborate with production companies may have more freedom when choosing which project(s) to work on; their choices could make a big impactful difference in how the final product comes out.
Hentai offers many genres, some so disturbing they have been banned in the US, as well as plenty of sexy and creepy content that's perfectly acceptable to watch, such as yuri or futanari. Tentacle porn is especially beloved among fans who like watching its tentacles move about freely and sensuously.
If you're curious to gain more knowledge of hentai, Japan hosts several conventions that specialize in it. Some events, like Hentai Con, are open to the general public while others allow creators to network with other anime and hentai professionals.