The Devil Is Too Cold and Needs to Be Warmed with Heart

She is the leader of the Demon Cult. It is said that she killed her father to become the leader. It is said that she has a heart of stone. He was the prince of the current dynasty, and was ordered to eradicate all evil forces in the world, but he fell to the point of giving up his principles and original intentions when he first met her. She wanted the world, so he conquered the world for her. If she wanted peace of mind, he ruined his martial arts, which was known as the best in the world, for her. He is her knight, giving up everything for her. And whether she is willing to let go of her guard for him, and whether she can return his pure and deep love...