Tres Marias: Sannin no Sei Shojo
English title: Holy Virgins
Japanese title: トレス・マリアス 3人の聖処女
Type: OVA
Source: Visual novel
Episodes: 2
Status: Finished Airing
Aired: Mar 16, 2001 to Jun 13, 2001
Duration: 31 min per ep
Rating: Rx - Hentai
Studios: Y.O.U.C
Producers: Digital Works
Licensors: Critical Mass Video
Genres: Hentai

The locals know all about Dr. Fuwa. His reputation for taking advantage of his female patients has left him little to do except his nurse Megumi. When he`s suddenly called in to investigate a mysterious illness that`s been affecting the nuns on a remote island, Dr. Fuwa`s certainly not above having a little fun with the patients – each and every one of them a cute little nun-in-training. But will he be able to uncover the truth behind their terrible condition? 

(Source: AniDB)