Fu Long Wei Hou

An emperor risks his life by diving into a lake to rescue his empress. There, he deceives a Xuan Long, persuading him to come to the palace and offering him in return. The Xuan Long grows to genuinely love the emperor through repeated interactions. Eventually, the emperor kills the Xuan Long, who vanishes after giving birth to a dragon. At that moment, the emperor regains his past memories and recognizes the Xuan Long as his long-lost lover, the one he had sought for millennia.