Uchi no Ojou-sama no Hanashi wo Kiitekure ~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 risque way, he comes to realize that she's a lot easier than she looks...