Wicked fox
(Book)

Series information from Goodreads.com.

Gu Miyoung is a gumiho, a nine-tailed fox who must devour the energy of men in order to survive. The modern city of Seoul is the perfect place to hide and hunt. After feeding one full moon, Miyoung crosses paths with Jihoon, a human boy, being attacked by a goblin deep in the forest. She violates the rules of survival to rescue the boy, losing her fox bead-- her gumiho soul-- in the process. Jihoon saw her nine tails, but he's drawn to her anyway. Their a tenuous friendship blossoms into something more... until a young shaman tries to reunite Miyoung with her bead. Now Miyoung must choose between her immortal life-- and Jihoon's. -- adapted from jacket