In recent years, Japanese films of this genre have become more common in the USA and Europe although it still remains a small, fetish-oriented part of the adult film industry. In some areas, there are laws stating it is not gaysex legally possible to consent to be killed, and elsewhere it may still be legally dubious . Arguably the most famous example of the genre is the Taboo series. Consent is the most important criterion here. Body parts including fingers, tongue and penis may be used for anonymous oral, vaginal and/or anal intercourse. BDSM has become an umbrella term for certain hentai videos kinds of erotic behavior between consenting adults. This yields a view that would not be obtainable directly through the eyes of a person while experiencing the sex act. Jail/Prison/Police pornography involves people in police custody or inmates in jails or prisons in various sexual situations, such as strip searches or body cavity searches. See Gay-for-pay. The nipples are erogenous zones, and vigorous stimulation of them during masturbation usually causes the penis to become erect more quickly than it would otherwise. Gang bang pornography is a type of pornography that depicts an individual engaging in physical sexual activity with multiple partners sequentially or at once. The terms porn milf can be complimentary or pejorative. High heel pornography involves women or men dressed in high heeled shoes. There is also some evidence that pornography can be used to treat voyeurism. Bukkake pornography usually depicts numerous men having sex with one woman, with multiple, usually 10 or more, men ejaculating on the female face. Group sex can occur between people of all sexual orientations and genders. For other scenes, particularly in established relationships, a safeword may be agreed to signify a warning rather than explicit withdrawal of consent; and a few choose not to use a safeword at all. The speed of the hand motion will vary from person to person, although it is not uncommon for the speed to increase as ejaculation nears and for it to decrease during the ejaculation itself.