Shin Woo Yeo is a handsome and smart professor. He is also a 999-year-old nine-tailed fox. To become a human, he collects human energy in a bead. Soon, he is set to become a human. Meanwhile, Lee Dam is a university student. One day, her drunk friend falls asleep on top of an expensive car. She apologizes to Shin Woo Yeo, who is the car owner. While Lee Dam struggles to take her friend away, Shin Woo Yeo gives her a hand. An accident happens that changes their fate. Shin Woo Yeo’s bead falls out of his mouth and Lee Dam unintentionally swallows it. The bead can exist inside of a human for no more than 1 year and, afterwards, the bead will break inside of that person. This will cause Lee Dam to die and Shin Woo Yeo will lose his chance to become a human. Shin Woo Yeo explains to Lee Dam their predicament and suggests that they should live together until they figure out a solution. Lee Dam, who has never had a boyfriend in her life, now lives with Shin Woo Yeo.