Gibo
English name: Stepmother's Sin
Genres: Drama, Romance, Hentai
Type: OVA, Episodes: 2
Aired: Oct 5, 2001 to Jan 11, 2002
Studio: Y.O.U.C
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
Yusuke's been very naughty. He's seduced his father's fiancee; transforming her into a debased slave to his own twisted desires. But as his hold on her tightens, his sanity slips, and the forbidden family fun descends into a nightmare of lust! Trapped in madness of their own creation, they will pay the ultimate price for a stepmother's sin!

(Source: RightStuf)