Nanase Ren
Genres: Hentai
Type: OVA, Episodes: 1
Aired: Dec 4, 2005
Studio: Flavors Soft
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
This will appear to be a very disturbing animation to most. Designs by Murakami Teruaki, published by Soft by Demand (Anime), and based on the eroge by M no Violet.

(Source: Bakunyuu)

Note:

There are 2(!) Nanase Ren OVA. Produced by totally different studios, but both feature the same(!) character. The other one is the "Kranke Nanase Ren" (夜勤病棟　Kranke　七瀬恋) bit, which is a special for Yakin Byouto

(Source: AniDB)