DISCODE

^{Futaba is a high school girl who has a strong sexual desire and she plays with herself at any place and anytime.

However, she has a dark secret that no one knows…

Source: AnimeNfo}

DISCODE 異常性愛 (Discode Ijousei Ai)
メーカー: D3 2004-2005
Three Episode OVA, futanari content animated in episodes one and three (第1章,第3章).

LINDA is the original character designer of this series which started under Courreges (クレージュ) as an eroge.
The eroge series consists of multiple titles:

DISCODE-1 異常性愛 (誘い受アドベンチャー)
DISCODE-2 二律背反 (フタナリアドベンチャー)
DISCODE surface (白濁液ぶっかけ誘い受アドベンチャー)
DISCODE reverse (白濁液ぶっかけ誘い受アドベンチャー)

If you are wondering which of the female couple is of note… that would be the redhead, Higuchi Futaba 「樋口二葉」. Unfortunately she only makes appearances in the OVA series and DISCODE-2 (have not seen in Vitamin L doujinshi either). Regardless, as a character, Futaba should be hailed…