Angel of Darkness is a 4 part hentai anime series released in 1994 by Pink Pineapple in Japan. The series focuses on tentacle rape and S&M and was adapted into a live action series. The animated series is released in North America by ADV Films under their SoftCel Pictures label. The genre is situated between sci-fi horror and the slasher film.
Each of the 4 part series had different styles and character designs.