Masturbation has been depicted in art since prehistoric times and is mentioned and discussed in very early writings. Group sex can occur between people of all sexual orientations and genders. In straight pornography, intercourse is often followed by a facial, pearl necklace or other visible ejaculation. The essence of voyeurism is the observing but may also involve hentai sex the making of a secret photograph or video of the subject during an intimate activity. Typically features nude milfs a feminine Uke, or submissive, and a masculine Seme, or dominative. The interaction between tops and bottoms—where physical or mental control of the bottom is surrendered to the top—is sometimes known as power exchange, whether in the context of an encounter or a relationship. When all regions of the face are included, facial cum shots comprise approximately 62% of scenes where external ejaculation occurs. Bestiality pornography involves the sexual videos gays attraction of humans to animals. Pornography can be classified according to the physical characteristics of the participants, fetish, sexual orientation, etc., as well as the types of sexual activity featured. Weather Report Girl is considered yuri hentai in English usage for its depiction of lesbian sex, but in Japan it is just yuri. Bareback sex is physical sexual activity, especially sexual penetration, without the use of a condom. It is also often mixed with other fetishes in practice, such as voyeurism, denial, etc. Ethnic pornography is a genre of pornography that features performers of specific ethnic groups, or depictions of interracial sexual activity. The fundamental principles for the exercise of BDSM require that it should be performed with the informed consent of all involved parties. Seconds after being deposited onto the face, the semen thickens, before liquefying 15–30 minutes later. Although macrophilia literally translates to simply a lover of large, in the context of a sexual fantasy it is used to mean someone who attracted to beings larger than themselves.