Guro or Gore is a genre of Japanese pornography involving blood, gore, disfiguration, violence, mutilation, urine, enemas, or feces. The work of Bruce Seven has been called reality porn, due to his lack of using scripts and asking his performers to act naturally in their own character. Going back at least as far as the Christy twins in the 1970s, depictions of incest and particularly incest between twins has been a feature of gay pornography. Animal masturbation has been observed in many gay twinks species, both in the wild and in captivity. In addition to mainstream pornography, the popularity of facials has led to creation of its own niche market, like video series that specialize in showing the act. 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. Internal ejaculations, followed by images of semen dripping from the anus, are sometimes depicted in bareback gay pornography, where they are referred to by the term breeding or the reverse money shot. Such films continued to be produced but could only be distributed by underground channels. Transsexual porn star Wendy Williams has stated hentai porn that transsexual porn is classified as Straight Specialty. 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. Female ejaculation is the expulsion of fluid by the paraurethral ducts through and around the human female urethra during or before an orgasm. It is mutual consent that makes a clear legal and ethical distinction between BDSM and such crimes as sexual assault or domestic violence. It spawned numerous sequels, several of which won adult film awards. In pornography, depictions of lesbian sex big tit milf form a popular subgenre, directed toward a male heterosexual and female homosexual audience. Real enema shots or videos of true medical situations may violate privacy laws in some countries.