Eiyuu x Maou by Escu de - Adult Sex Game

You are Falsir, the lord of the demons. For a long time, your race lived in peace with humans, but one day your butler Galef told you bad news: Humans have begun to attack your lands!
As you fight them, you will learn that the reason they want to destroy you is simply because they see you as a threat. If they want to see the lord of demons, so be it, and your dear servants, whom you have to fertilize to make your army stronger, will help you, because they will "give birth" to you an army worthy of the lord!