Hentai is a Japanese word that literally means "strange appearance", but also means "perverted". Hentai, because of this, is a word used by countries outside of Japan to show porn and sex-related anime, manga and video games. The word is not used to mean this in Japan. In Japan, terms such as ecchi are used.
The word hentai is sometimes used to apply to cartoon characters that are not anime characters. Hentai is the anime version of porn. There is on screen sex, often very graphic and very imaginative. Since hentai is anime, the performers are not bound by physical laws. Makers of hentai often use this in very creative ways. Some of the acts performed in hentai would be physically impossible. Some of the performers are often impossible themselves. Fairies, monsters, and even new and strange creatures are stars of hentai. Monsters and demons with tentacles are seen so often that “tentacle porn” is its own sub-category of hentai.
Most of the hentai (anime)-films in the late 1990s to the present day are based on Ero-Games, where the only actual goal is to date the girls in the game and have sex with one of them. The games feature various character-types, like a bookworm, a tough girl, a younger girl, and a tomboy. Ero-games can include highly taboo themes, such as (coprophillia or dismemberment and pedophilia) and sometimes less taboo subjects, such as (incest, rape). Some examples of these kind of game-to-hentai-anime conversions are Immoral Sisters, Isaku, Pia Carrot, Five Card, Bible Black, Words Worth, Night Shift Nurses, and Milk Junkies.
Famous hentai films include: