Seven-year-old Dong-i, abandoned by her family, has her life saved by a goblin in the mountains. Taking pity on the child, the goblin disguises himself as a distant uncle to look after her. Twelve years later, Dong-i has blossomed into the most beautiful woman in the village. Though villagers try to arrange a marriage for her, she rejects them all, having long harbored feelings for the 'uncle' who raised her—feelings he consistently ignores. One dawn, Dong-i follows her suspicious uncle and witnesses him drinking horse blood. After the initial shock, she realizes he is the very goblin who saved her as a child and begins to pursue him earnestly. However, the goblin, having stayed in the human world too long, is on the verge of becoming a monster. He pushes her away, claiming that to prevent his transformation, he must mate with a woman possessing strong yin energy... "Uncle, then do it with me. That 'mating' thing."
