She was just a little girl with yellow hair who wanted to have fun and wanted to be a female detective. He was the young master of the Demon Cult who was burdened with a blood feud. He was the king of a country who had the world in his heart but was ruthless. What kind of unsolved case entangled the fate of the three people together. Years later, she was no longer that simple girl. He gave up the world just for her. If you don't abandon me, I will depend on each other for life and death. One person devotes his whole life to him, just to get her smile like a flower. How should she choose? After many years of separation and long love, is there a red luan that will make them stay together forever and never separate...