My Girlfriend is a Gumiho (2010)

Cha Dae Woong accidentally releases a troublesome Gumiho, a legendary fox with nine tails, sealed inside a painting. Fleeing the scene, Dae Woong suffers a life-threatening fall and is only saved by the Gumiho, who gives him her "fox bead". When Dae Woong awake and meet a mysterious pretty girl, he initially treat her as eccentric or mentally ill, before fully understanding that she is a Gumiho in disguise. He agrees to stay with her and he tries to keep her happy, while hiding her true identity as a Gumiho from others by introducing her as his friend, Mi Ho. Slowly, however, he becomes less scared of her and more protective of her, and finally admitting to himself and to her that he loves her. As the story unfolds, Mi Ho pursues her goal of becoming human and stays with Dae Woong.

Source: TMDb