Uchi no Ojousama no Hanashi wo Kiite Kure: Akuyaku Reijou Kouryaku Kiroku

Crow, the loyal butler of a villainess, realizes through a series of chance events that he has in fact been reincarnated into another world. With a new perspective on life, he realizes just how badly he's been treated by this haughty, egotistical and prideful noble lady he calls his mistress until now, and boils with rage at the injustice. However, after deciding to take revenge on her in a risqué way, he comes to realize that she's a lot easier than she looks... This is a story of how a reincarnated butler tames his villainous mistress in lustful ways, but ends up making her truly happy. (Source: Kill Time Communication, translated)