Immortal Palace Transformation

He is the prince of the demon world, reincarnated into the mortal world just to untie the poison of alienation in his soul. She is the only heir to the fairy palace, and is ordered by her father to regain the lost land in the world. Their marriage is destined to be separated and reunited, and their love and hatred are entangled. Will it fulfill a thousand-year curse, or will it unify the three realms and create a harmonious new world?