Others may also use vibrators and other sexual devices more commonly associated with female masturbation. Pornographic lesbian hentai films present sexual fantasies and usually include erotically stimulating material such as nudity. The person sat upon may be in bondage, sexually submissive, or simply held down by the body-weight of the other person. 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. After the prerequisite level of sexual stimulation has been achieved, and ejaculation becomes imminent, the male will position his penis so that the semen discharged will be deposited onto his partner face. Squirt pornography involves women ejaculating. Within a BDSM or D/s context, facesitting can be an especially intense form of erotic humiliation. Enema pornography involves adults gay twinks given big tit milf enemas to others, often fake. Other possibilities are possible, such as a man having sex with two women who are having sex with each other. Some do not use the diapers at all, for arousal, or bladder and bowel movements. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. One-sided male nudity can also arise when a male disrobes as part of a male striptease. These scenes may either have the cameraman directly engaging in sex or merely filming others having sex. While most tentacle erotica is animated, there are also a few live-action movies. Some BDSM practitioners prefer a code of behavior that differs from SSC and is described as risk aware consensual kink , indicating a preference for a style in which the individual responsibility of the involved parties is emphasized more strongly, with each participant being responsible for his or her own well-being.
