Youjuu Kyoushitsu
English name: Demon Beast Invasion
Genres: Horror, Hentai
Type: OVA, Episodes: 6
Aired: May 25, 1990 to May 27, 1994
Source: Manga
Rating: Rx - Hentai
Synopsis:
Demons take multiple forms, in this case there's one thats the mightest of all and has to be satisfied with the flesh of woman. He searches for his preys in the form of a woman, so they won't be feared. 

(Source: ANN)