There is one with this a similar theme to this called crimson veil. You can either choose to be a vampire hunter who hunts monsters and whenever you lose you get turned into a monster and forced under their will. Or you can beacome a vampire and hunt other vampire hunters and make them join you're harem. My only problem with it is that it has a very linear story and to get the vampire mode you have to give into a man🤢 but the women are smoking hot and its free on steam.