John Stagliano is considered to have started the gonzo pornography genre with his Buttman series of films. For circumcised males, on whom the glans is mostly or completely uncovered, this technique creates more direct contact between the hand and the glans. Internationally, lesbian milfs hentai is a catch-all term to describe a genre of anime and manga pornography. Women with women Main article: Lesbianism in erotica: Lesbianism in contemporary pornography Lesbian or girl-girl pornography features women engaged in sex together, but is typically aimed at a male audience. Pornography in Japan is large and intertwined business of adult entertainment with unique characteristics that readily distinguish it from western pornography. Bondage/BDSM Bondage pornography features performers tied up or constrained in various ways. Concerted deployed sexual rejection exercised on the partner can be an aspect of Dominance and Submission as well. If dramatic skills are not gay sex video involved, a performer in a porn film may also be called a model. Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime . Some men also enjoy anal stimulation, with fingers or otherwise, without any prostate stimulation. Though there have been numerous gang bang pornographic films since the 1980s, they usually involved no more than half a dozen to a dozen men. 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. Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black gay hentai descent are promiscuous, and their buttocks are objectified by porn as a result.