Haechi’S Princess summary: The unfortunate Princess Soyang, who lived as the daughter of the dethroned Rain. Threatened by those who aim for the legendary ring. By fate, she meets Haechi, gets help, and builds a relationship... 300 years later, Korea, Youngkwang Lee, the curator in charge of the ''Princess Soyang and Haechi" exhibition, picks up an unusual cat. But this cat, who speaks even human words, is actually harming him... ?!