A Blossoming love between a demon and a Prince

My parents had me nailed inside a coffin for a ghost marriage because they said I was blocking my twin brother's luck. I tried my hardest to break open the coffin, but the jade pendant in my hand started to heat up and a voice inside said it could save me, but only if I agreed to marry it. In order not to marry the persistent, deceased, perverted man who had been pursuing me, I agreed to marry the jade pendant. To my surprise, a person was hidden within the jade pendant. This person was the root of everything. Even the man chasing after me had ulterior motives.