In Japan, point of view pornography is referred to as hamedori . The consensual submission of the submissive is sometimes demonstrated to others by symbols indicating his/her belonging to the dominant, such as wearing a collar, special tattoos, piercings, a very short haircut or a bald head. Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals. Sadism describes sexual pleasure derived by inflicting pain, degradation, humiliation on another person or causing another person to suffer. Diaper fetishism, nappy fetishism or diaperism, is a 3d hentai sexual fetish in which a person feels a desire to wear or use diapers. Lying face down on a comfortable surface such as a mattress or pillow, the penis can be rubbed against it. In these research publications, it is suggested that real female ejaculation is the release of a very scanty, thick, and whitish fluid from the female prostate, while the squirting or gushing shown frequently in pornography is a different phenomenon, the expulsion of clear and abundant fluid, which has been shown to be a diluted fluid from the urinary bladder. Bukkake pornography involves a performer, usually female, onto whom several men or women ejaculate, usually on the face. The term has origins in the Greek language . Standing up, a chair, the corner of an item of furniture, or even a washing machine can be used to stimulate gay twinks the clitoris through the labia and clothing. Mutual masturbation, mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. While wearing horny milfs diapers, a diaper fetishist generally experiences a comforting feeling. The term has also applied to other professions and even companies trying to appeal to a gay demographic. Interactive pornography, available in CD-ROM and DVD format, allows the viewer to select the particular acts performed at any one time, sometimes with the camera providing a first person view.