Cha Dae Woong (Lee Seung Gi) is a student at an action school, raised by his wealthy grandfather and aunt. While his grandfather would like nothing more than for Dae Woong to marry quickly and give him grandchildren, Dae Woong himself only wants to play! His life changes forever when he visits a shrine and sees a painting of a gumiho (nine-tailed fox), whom a monk tells him was imprisoned there by the Three-god Grandmother. Suddenly there is a thunderstorm, and Dae Woong’s phone runs out of battery. Yet he is startled when a mysterious voice talks to him and tells him to draw nine tails on the fox in the painting. She tells him that she’s the gumiho in the painting, and was released thanks to him! Before he leaves the temple’s grounds, Dae Woong injures himself badly. Sensing his impending doom and wanting to repay him for her freedom, Mi Ho gives him her fox bead, which will keep him alive. He tries to get rid of her, but Mi Ho follows him all the way to Seoul. What will Dae Woong do with a 500-year-old myth following him around and always begging for meat?!
Wi Mae Ri (Moon Geun Young) is a young woman living with her widowed father. The two of them spend their time running away from loan sharks, and Mae Ri has even given up university in order to find a job and help her father. Mae Ri accidentally hits the beautiful indie musician, Kang Moo Kyul (Jang Geun Suk). Meanwhile, an old family friend returns to Korea from Japan and wants to betroth his son, Byun Jung In (Kim Jae Wook) to Mae Ri! Moo Kyul’s ex-girlfriend Seo Joon (Kim Hyo Jin) shows up and becomes the lead actress in Jung In’s drama, but will only be his friend if Mu Kyul is single!
Kim Yoon Hee (Park Min Young) is a daughter of the Joseon era who is used to dressing up as a man. Her father is dead and her sick younger brother is unable to work, so who else will support the family? She works as a scribe who makes study guides for students, and is even paid to take tests in their place. But when she mistakes the Left State Minister’s uptight son, Lee Sun Joon (Yoochun) for the person she’s supposed to help cheat, she forms an unlikely friendship with him and enters the prestigious Sungkyunkwan University under her brother’s name. She and Lee Sun Joon share a room with the rebellious upperclassman Moon Jae Shin (Yoo Ah In), nicknamed “Crazy Horse.” She also meets the fashionable playboy Goo Yong Ha (Song Joongki). The four form an unlikely bond, but will the knowledge that she’s a girl ruin everything for them?