Have you ever wondered, looking fearfully at the full moon at night, where do gumihos come from? Eighteen-year-old Miyeon has a secret - she is a gumiho, a nine-tailed fox. To survive, she needs to devour the energy of men. Seoul is the perfect city for this, because no one will believe that the dark tales are actually true. But one day everything changes. One terrible night, Miyeon saves Jihoon, a young man who falls victim to a goblin. Against her better judgment, she helps him, and pays cruelly for it. Their fragile friendship gradually blossoms into something magical, but, as in any fairy tale, the heroine is faced with a choice: immortal life or Jihoon. What will she choose?