Gibomai
English title: Step Sister
Japanese title: 犠母妹
Type: OVA
Episodes: 2
Source: Visual novel
Genres: Hentai
Studios: Mook Animation
Producers: Discovery
Duration: 28 min per ep
Rating: Rx - Hentai

A renowned painter dies of heart disease while being married with Megumi, a woman much younger than he is. His son, Kyosuke, never liked that union and wants Megumi out of the house. Therefore Megumi proposes that Kyosuke can do anything he wants with her daughter Yuna, Kyosuke's stepsister, if he allows them to stay. Naturally, Kyosuke accepts.

(Source: AniDB)