Seducing the Monster Duke

About 20 years in future, the world will be in ruins because of the invasion of the beasts. There's only one way to stop the destruction: marry the "monstrous" duke and bear his hero-to-be child! Upon glimpsing the future, Elena succeeded in marrying him, but... "You may be my wife, but I won't lay a single finger on you." She wanted to get it quickly out of the way, but her husband's impregnable fortress is stronger than she could have imagined! Will Elena be able to safely give birth to the hero and save the world?