I played this game a while ago, i can't seem to find it.
The MC(Male Protagonist) has a sex fairy/succubus. He can command the fairy/succubus to manupulate the women around the MC, so he has sex with them.
Good recommendation. Thanks. But I haven't played this game before.
Another detail is that, if the MC doesn't corrupt the women, the fairy becomes evil & take control of MC's life.
I almost thought Long Live the Princess as well, but the description of the "fairy" doesn't quite match how Belle is in the VN. In Long Live the Princess, Belle mostly plays the role of a comrade (with benefits, lol), not someone who would turn evil. If anything, she shows her kinder side the more the game progresses.
There is another possibility: Luxuria.
This one is made using the Honey Select rendering. And, this game has an ending where you let the succubus complete her plan and the MC becomes some sort of demon. Perhaps this is the one?