Chae Dae Wong, an aspiring actor, unwillingly releases a Gumiho, a legendary nine-tailed fox, from her centuries-old prison. He runs away terrified and ends up injuring himself badly, but she saves his life and asks to stay by his side.

Cha Dae-woong (Lee Seung Gi) accidentally releases a troublesome gumiho, a legendary fox with nine tails, sealed inside a painting by Grandma Samshin . Fleeing the scene, Dae-woong suffers a life-threatening fall and is only saved by the gumiho giving him her "fox bead". When Dae-woong awakes and meets a mysterious pretty girl, he initially treats her as eccentric or mentally ill, before fully understanding she is a gumiho in disguise-at which point he tries to research gumihos, but fails to find correct information in the library or on the internet. He agrees to stay with her and he tries to keep her happy, while hiding her true identity as a gumiho from all others by introducing her as his friend, Mi Ho. Slowly, however, he becomes less scared of her and more protective of her-finally admitting to himself and to her that he loves her. As the story unfolds, Mi Ho (Shin Min Ah) pursues her goal of becoming human, with the half-human, half-supernatural Park Dong Joo, who has a career as a veterinarian and has been living as a half-human for hundreds of years, informing her that to do so, she must drink his blood and allow a human to keep her fox bead inside their body for a full 100 days - faithfully entering into a Love Contract, and keeping the bead from being harmed by remaining chaste. However, Dong Joo does not mention that at the end of the 100 days the human will die. Mi Ho and Dae Woong fall in love without fully knowing the consequences of fulfilling her goal: namely, that Woong will die if she becomes fully human.—Wikipedia

500 years ago, a Gumiho, a legendary nine tailed fox that could take the form of a beautiful woman, wished to become human. However, a rumor spread that she only wanted to seduce men to eat their intestines, and so she was locked away in an old temple for centuries. On our present day, Chae Dae Wong, an irresponsible, aspiring young actor, arrives there by chance and unwillingly sets the Gumiho free. Terrified by all the legends about blood thirsty gumihos, he ends up hurting himself badly while trying to run away. When he regains consciousness, he sees a beautiful young woman who claims she's the Gumiho and that she's just saved his life. Dae Wong thinks she's crazy and tries to ditch her, but she doesn't want to return to her captivity and asks to remain with him.—Dama del Puente