But the last episode (the last episode of the story introduction: online search)
Wang Yuanfeng and Xiaocui are very sweet in the Wangs' yard. The king gave advice, but came to persuade Wang Yuanfeng to return to the palace to take charge of politics. Wang Yuanfeng was very reluctant. Xian Fenghua and Yi Ya arrived at this moment. They told Wang Yuanfeng a shocking news: Xian Fenghua is a real prince.
It turns out that according to monster hunt, when Wang Taichang took out the prince who turned into a civet cat from the palace, he wrote to inform the couple who caught the demon fairy to enter Beijing. He handed the civet cat prince to the Xian couple, who said that only by sucking the demon blood of the prince could they become human again. Wang Taichang was loyal, regardless of his own safety, and helped the prince suck the demon blood dry. He knew that he would soon be poisoned and demonized, so he entrusted the prince to the virtuous couple to raise him. He himself hurried home to Queen Li See, who had just given birth to his son. Because of the demon change, he had to abandon his wife and children and hide in Tibet.
This is my answer, and I hope it will be adopted.