It's a long story.
Lian Qianqiu, as the eldest daughter of the emperor, with a noble status, was supposed to have a smooth life with few disappointments, but she happened to meet him, and he had someone else in his eyes. She can use her imperial power to make anyone compromise but is unwilling to restrain him. So she drove away the person he loved most, hoping to use all her feelings to melt him, even if it took a lifetime of waiting.
Shang Tiancheng, a young and promising general, became the eldest princess's companion at the age of 9. As a result, he met the person he longed for, but he never had the chance to stay with her. Hate? He doesn't hate. Because he is a minister and she is a king. He promised to protect her, be loyal to her, and get whatever he wanted for her, but what she wanted was her heart, the only thing that belonged to him, and he didn't want to give it away easily.
PS: The heroine is absolutely noble but also absolutely infatuated.