Main

• Lee Seung-gi as Cha Dae-woong
  • Hyunwoo as young Cha Dae-woong

An immature aspiring actor who lost his parents at a young age, and was subsequently raised by his affluent grandfather and aunt. When his grandfather tries to enroll him in a strict boarding school, Dae-woong runs away and eventually ends up at a Buddhist temple, where a woman's voice tells him to draw nine tails on a painting of a fox. He then meets a girl who informs him that she was the gumiho in the painting (he later calls her Mi-ho). 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.

• Shin Min-a as Gu Mi-ho/Park Seon-ju/Gil-dal

A legendary nine-tailed fox (or "gumiho" in Korean mythology) who was sealed inside a painting for 500 years. She has dreamed of becoming a human for centuries, but once rumors spread that she's a femme fatale who eats men's livers, and no human man would agree to marry her. 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. After Dae-woong has an almost fatal fall from a cliff, she gives him her fox bead to keep him alive.

• No Min-woo as Park Dong-joo

A half-human, half-supernatural being who disguises himself as an ordinary veterinarian. His initial mission was to capture the gumiho and put her back into the painting, but upon seeing Mi-ho, he changes his mind as she is the spitting image of Gil-dal, a goblin he'd once loved centuries ago, who was betrayed by her human lover and died at Dong-joo's hand. Suspecting that Mi-ho is Gil-dal's reincarnation, he acts as her mentor, watching over her and supplying her with information about humans. He also constantly warns her that humans cannot be trusted. Dong-joo tells Mi-ho how she can become human, deliberately withholding the fact that Dae-woong will die in the process. He readies all the necessary identifications and papers under the name "Park Seon-joo," which Mi-ho would assume once the 100 days have passed and she's become fully human. He also started to have feelings for Mi-ho.

• Park Soo-jin as Eun Hye-in

Dae-woong's older classmate and love interest whom he calls "noona"; Dae-woong stopped liking Hye-in after spending some time with Mi-ho. When Mi-ho becomes Dae-woong's girlfriend, she becomes jealous, and attempts to throw a wrench into their relationship by investigating Mi-ho's true identity.

Supporting

• Sung Dong-il as Ban Doo-hong

Stunt director and head of the action school that Dae-woong attends. He is also the widowed father of Ban Sun-nyeo. Doo-hong idolizes Hong Kong star Chow Yun-fat and tries to imitate him in his appearance and manner of speaking. He falls for Dae-woong's aunt Cha Min-sook.

• Yoon Yoo-sun as Cha Min-sook

Dae-woong's aunt. She was never married and is very obedient to her father. She's unable to express her feelings for Ban Doo-hong, causing her to often make a fool of herself in his presence.

• Byun Hee-bong as Cha Poong

Dae-woong's strict but loving grandfather. He's concerned that his spoiled and shallow grandson isn't making good choices in life. He becomes fond of Mi-ho upon meeting her, and sees that being with her has made Dae-woong more mature and responsible. He eventually accepts Dae-woong's dream of becoming an actor.

• Kim Ho-chang as Kim Byung-soo

Dae-woong's best friend and classmate in action school. He is supportive of Dae-woong, and secretly likes Sun-nyeo.

• Hyomin as Ban Sun-nyeo

Dae-woong's friend and the daughter of Ban Doo-hong. After she gets over her crush on Dae-woong, she finally realizes that Byung-soo likes her and reciprocates his love.

Special appearances

• Im Hyun-sik as Buddhist monk (ep 1, 8, 15)
• Lee Soo-geun as police officer (ep 4)
• Uee as art major in college (ep 5)^[6]
• Park Shin-hye as Go Mi-nyeo (ep 6)^[6]
• Lee Hong-gi as Jeremy (ep 16)^[6]
• Kim Ji-young as Samshin grandmother (ep 15, 16)

Part 1^[7]

Part 2^[7]

Part 3^[7]

Part 4^[7]

Part 5^[7]