Mugen no Kyoukai
English title: The Boundary between Dream and Reality
Japanese title: 夢現の境界
Type: OVA
Source: Visual novel
Episodes: 4
Status: Finished Airing
Aired: Oct 28, 2000 to Jul 18, 2001
Duration: 28 min per ep
Rating: Rx - Hentai
Studios: Mikimoto Production
Producers: Five Ways
Genres: Fantasy, Supernatural, Hentai

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)