In the context of consensual erotic activities, sadism and masochism are not strictly accurate terms; there is a significant difference from the medical or psychological usage of both terms. Can also include auto-fellatio, or performing oral sex on oneself. Tentacle rape or shokushu goukan is found in some horror or hentai titles, with tentacled creatures having sexual intercourse with female characters. A variant of A2M is ATOM where a performer inserts his penis directly from one recipient anus into a second recipient mouth. Men may find stimulation of the anus, rectum, and adjacent organs enjoyable. Omorashi: The act of holding one own urine until the need to urinate is urgent, making another hold in their urine, or watching another person with an urgent need to urinate. Twink pornography features younger performers, and usually features young men under 30 who identify as gay or bisexual. One or more of the participants may engage in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. Watersports pornography features sexual activities involving urine, such as golden showers. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual gay twink porn orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. Snuff pornography involves the actual death of any of the participants, consenting or otherwise, simulated death is not considered snuff. Hentai is the various forms of Japanese pornography, including H-manga, H-anime, and H-computer games. This anime hentai style of filming is in contrast to having a separate, third-person camera crew filming all the action. Squirt pornography involves women ejaculating. Pegging is a sexual practice in which a woman momporn performs anal sex on a man by penetrating the man anus with a strap-on dildo. As a result, little in history was documented to give an accurate description of how female homosexuality is expressed.