Related genres include: Amateur pornography originally referred only to pornography produced by amateurs but now also includes professionally made pornography designed to appear as if it were amateur. As in B/D, the declaration of the Top/Bottom may be required, though sadomasochists may also play without any Power Exchange at all, with both partners equally in control of the play. Simultaneous penetration of the mouth and either the vagina or anus. A female dominant in a master/slave relationship is often termed a Mistress, not to be confused with the colloquial usage of mistress as a kept sexual partner without a similarly formalized power relationship. It may be regarded as taboo or unnatural, and is a criminal offense in some countries, punishable by corporal or capital punishment; by contrast, people also regard anal sex as a natural and valid form of sexual activity that may be as equally fulfilling as any other desired sexual expression. Unlike erotic films, pornographic films contain explicit sexuality and do not claim any artistic merit. Guro or Gore is a genre of Japanese pornography involving blood, gore, disfiguration, violence, mutilation, urine, enemas, or feces. Initially, few animation studios in the United States attempted to produce animation for adult audiences, but later examples of animation produced for adults would gain mainstream attention and success. Some techniques which may work for one individual can be difficult or uncomfortable for another. Amateur porn has been called one of the most profitable and long-lasting genres videos gays naked celebrities of pornography. Given the wide range of practices, lesbian hentai some of which may be engaged in by people who do not consider themselves as practicing BDSM, inclusion in the BDSM community or subculture is usually dependent on porn milf self-identification and shared experience. It gay cock can be combined with fellatio and the woman may move her breasts up and down on the penis for an additional stimulation, usually before the man reaches orgasm. This style of filming is in contrast to having a separate, third-person camera crew filming all the action.