My Harem Is Entirely Female Demon Villains

Adapted from the novel [After Being Proposed To By The Villain]. A human being from another world, crossed over as a hero… into the bed of the female demon villain?! If I hadn't established marriage contracts with all the villains in the game before crossing over into its word, I'd be a dead man. Now the villains are pestering me, making me assist them in dominating the world, contending for my hand in marriage, what should I do?! Stuck in the game… emergency!!!