While walking down the street with a friend, Dami accidentally swallows Woo-yeo's fox bead. The next day, Dami moves in with Woo-yeo, hoping to find a way to return the fox bead to him.
Dami is shocked to know she could die if she fails to get the fox bead out of her body within a year, and Woo-yeo writes a contract to protect Dami and the bead. Dami struggles to survive among men who were born in the Year of the Tiger.
Dam suspects that she might have an arrhythmia when these strange new feelings arise. The problem is Woo-yeo also feels something strange. But, the budding romance doesn't last long.
Jae-Jin sets Dam up on a blind date. Dam's mother shows up for a surprise visit, forcing Dam and Woo-Yeo to explain their relationship. Woo-Yeo contemplates whether it is fair to Dam to continue their relationship.
Woo-Yeo and Hye-Sun learn that a maegu, an evil spirit that a gumiho becomes if it fails to become a human within 1000 years, has been killing women who know Woo-Yeo. They decide to protect Dam from the maegu.
Woo-Yeo reclaims the marble without managing to erase Dam's memories of him. He reenters her life as her new history professor. They each realize that they miss the other.
The history department goes on a field trip, during which Woo-Yeo and Hye-Sun realize that Dam has retained her memories of her relationship with Woo-Yeo. Woo-Yeo and Hye-Sun rekindle their relationship.
Hye-Sun warns Woo-Yeo that physical contact with Dam drains Dam's energy. Woo-Yeo informs Dam that physical contact between them endangers her. Woo-Yeo and Dam try to maintain their relationship without touching each other.
The mountain spirit tethers Dam to Seon-Woo, which complicates the relationship between Woo-Yeo and Dam. Jae-Jin and Hye-Sun form a closer bond. Soo-Kyeong tries to process the evolving relationships in her friends' lives.
On a trip to interview a scholar, Dam realizes that Seon-Woo's affection for her is genuine. Dam resists Seon-Woo. However, her relationship with Woo-Yeo is put under strain when she learns that he has been seeing Professor Seo.
After Dam breaks off her relationship with Woo-Yeo and Jae-Jin concludes Hye-Sun likes Woo-Yeo, Dam and Jae-Jin pretend to be lovers to make their partners jealous. The mountain spirit tells Dam that Woo-Yeo needs her help to become human.
Dam and Woo-Yeo are photographed together, which forces their relationship out into the open. Dam tries to make Woo-Yeo more human by having him interact with her friends. Seon-Woo confesses his love to Dam.
After their relationship becomes intimate, Dam and Woo-Yeo find themselves unable to concentrate. Soo-Kyeong's secret is revealed. Jae-Jin and Hye-Sun become closer. Woo-Yeo learns he may disappear before he has a chance to become human.
