Netorare: Tanabe Yuuka no Dokuhaku

A housewife gets raped by a random guy and continues to have sex with him while her husband is away.

Netorare, used to define a genre of Eroge (Hentai Game), meaning "Cuckold". In short, the main protagonist's loved one(s) are taken or seduced away from him and the heroine might be willing ....