When Dae-woong awakes and meets a mysterious pretty girl, he initially treats her as eccentric or mentally ill, before finally understanding that she is a gumiho in human form.
Fearing that she would eat him, he tries to keep her happy by buying her meat (Korean beef in particular, her favorite) and hiding the fact that she's a gumiho from others.
As they spend more time together, he's surprised to see that instead of the ferocious figure of legend, Mi-ho is cute and full of wonder, and falls in love with Mi-ho.
Her gumiho energy will slowly empty away while her bead will live in the human for 100 days and take in his energy.
And when she reclaims her bead, she will become human.
As time passes, they get to know each other better and Dae-woong is charmed by how Mi-ho looks at the world with childlike wonder.
Enter Park Dong-joo (No Min-woo), a half-human, half-supernatural being, whose cover identity is as a working veterinarian.
Dong-joo tells Mi-ho that she'll be able to turn human if she follows these instructions: She must drink Dong-joo's blood then place her fox bead inside a human's body for 100 days.
Once she does this, her supernatural self will start to die, gradually.
She has superhuman strength, can run exceptionally fast, jump great heights, and can identify people and objects from great distances by smell.
However, she has a mortal fear of water, since her fox bead (which houses her life energy or "qi") is made from goblin fire).
Mi-ho and Dae-woong thus fall in love without knowing the consequences of fulfilling her goal: in 100 days, Dae-woong will die if Mi-ho becomes fully human, but Mi-ho will die if the bead isn't returned.