Mugen no Kyoukai
English name: The Boundary between Dream and Reality
Genres: Fantasy, Supernatural, Hentai
Type: OVA, Episodes: 4
Aired: Oct 28, 2000 to Jul 18, 2001
Studio: Mikimoto Production
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
The main character, Kengo, keeps having dreams of a strange world where different animal (and plant) women are being raped by strange monsters. Why is this and what is this strange dream world?

Before long it will become more than just a mere dream...

(Source: AniDB)