Originating in Japan in the 1980s, the genre subsequently spread to North America and Europe, and crossed over into gay pornography. One or more of the participants may engage in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. The anus has a relatively high concentration of nerve endings and can be an erogenous zone, and the receiver may receive pleasure from external anal stimulation. While bondage is a very popular variation within the larger field of BDSM, it is nevertheless sometimes differentiated from the rest of this field. Transsexual porn star Wendy Williams has stated that transsexual porn is classified as Straight Specialty. Reality pornography is professionally made porn which seeks to nude milfs emulate the style of amateur pornography. As of 2013, little analysis of this paraphilia has been reported in medical literature. See Gay-for-pay. Facial cum shots are currently regularly portrayed in pornographic films and videos, often as a way to close a scene. Sadomasochism does not imply enjoyment through causing or receiving pain in other situations . Guro or Gore is a genre of Japanese pornography involving blood, gore, disfiguration, violence, mutilation, urine, enemas, or feces. Bara male homosexual hentai designed to appeal to men. This may help them develop their orgasm, increase its pleasure, and may inspire them to masturbate on a more frequent basis. A somewhat controversial ejaculation control technique is to put pressure on the perineum, about halfway between the scrotum and the anus, just before ejaculating. BDSM is a variety of erotic practices involving dominance and submission, role-playing, restraint, and other interpersonal dynamics. Unlike the traditional definition of the term, in fetish usage a cuckold gay fuck is complicit in their partner sexual infidelity and hentai sex takes masochistic sexual pleasure in it. Actual upskirt or downblouse shots may violate privacy laws in some countries. If this is done using penises and/or strap-on dildos, this is sometimes called the sandwich or BigMac.