No one in modern-day Seoul believes in the old fables anymore, which makes it the perfect place to for Gu Miyoung and her mother to hide in plain sight. Mihoung is a Gumiho, a nine-tailed fox, who must eat the souls of men to survive. She feeds every full moon—eating the souls of men who have committed crimes, but have evaded justice. Her life is upended when she kills a dokkaebi, a murderous goblin, in the forest just to save the life of a stupid boy. But after Miyoung saves Jihoon's life, the two develop a tenuous friendship that blooms into romance forcing Miyoung to choose between her immortal life and Jihoon's.