Main •
Lee Seung-gi as Choi Kang-chi •
Jung Joon-won as young Choi Kang-chi :A half-man, half-
gumiho who longs to become fully human. He originally loved Chung-jo, but soon slowly fell in love with Yeo-Wool. •
Bae Suzy as Dam Yeo-wool :A martial arts instructor at her father's school, she is particularly skilled with a bow and arrow. When she was younger, Kang-chi saved her from being attacked by a dog, and she never forgot about him. She then falls in love with him when they meet again. She also accepts Kang-chi for who he is inside, even though he is a divine creature that many people are afraid of. •
Sung Joon as Gon :He has a one-sided love for Yeo-wool, for whom he serves as a bodyguard. He also has a bickering relationship with Kang-chi. •
Lee Yu-bi as Park Chung-jo :Kang-chi's first love. She is promised off to someone in marriage in order to sustain the family-owned-inn's longevity, hence the reason she originally first began spurning Kang-chi's open display of emotions towards her. After the family tragedy, she is forced to become a gisaeng. She makes a pact with Kang-chi that he should come and take her away from her current place once he has proven Lord Park's innocence. •
Yoo Yeon-seok as Park Tae-seo :A cool-headed, responsible scholar who helps his father, Mu-sol run their inn. He comes under a hypnotism that makes him think Kang-chi murdered his father, testing the bonds of their friendship and brotherhood.
Supporting •
Choi Jin-hyuk as Gu Wol-ryung :Kang-chi's father. He is the guardian spirit of
Mt. Jiri. He's fond of traveling outside to see the world and during one such travels comes across Seo Hwa and falls in love with her. They marry, but he keeps his identity hidden until it's revealed, and Seo hwa, being too young and fearful, betrays him with her impulsive actions. A betrayal which costs his 'life' since he loses the will to fight after finding out and doesn't fight back. :Not long after he's 'killed', his body 'dies' and stays still, hidden from everyone's eyes deep in the mountains for several years. After decades, he revives but as a '1000 year demon', stripped of his 'guardian spirit' status. This happens due to him breaking the 100-day oath he took, which he couldn't complete due to certain incidents. :Being a demon leads to him losing the ability to heal or revive. The only thing left was hatred, anger, destruction and death, causing him to go on a rampage, massacring several villages. :It also led to him having memory loss over time, which he predicts that once he's lost it all, he truly would become an agent of chaos, a true demon. To prevent that, he tries to force his son through threats and intimidation in hopes of being put at peace since the only one capable of killing the current him was his own blood, his son Kang-chi. :It isn't until his wife, Seo-hwa sacrifices herself by committing suicide and apologizes that he had a chance of becoming 'alive' again, not as a demon but as a mountain spirit. •
Yoon Se-ah as Yoon Seo-hwa (ep 14–21) •
Lee Yeon-hee as young Yoon Seo-hwa (ep 1–2, 21) :Kang-chi's mother. She is the daughter of a nobleman who becomes a
gisaeng after her father is framed for treason and killed but gets saved by Wol-ryung, who protects and eventually marries her. :She becomes afraid and angry towards Wol-ryung after learning of his true identity and, in impulsiveness, anger and fear, sells off his living place to soldiers, eventually 'killing' him. She tries to get rid of the child inside her womb in fear of it being a monster but fails. She eventually gives birth to the child(Kan-chi) and regrets her actions, asking him not to forgive her. After leaving her son in the monk's care, she goes off to die as her punishment, but survives and disappears. :She returns years later disguised as a Japanese lad,y Ja Hong-myung, and secretly plans her revenge against Jo Gwan-woong but finds her missing son and learns of her husband being alive but amnesic, having turned into a demon mainly due to her actions. :She stops Wol-ryung from causing any more havoc and apologizes for everything that happened. In the end, she commits suicide in order to truly bring Wol-ryung back to life, not as a demon but as a guardian spirit. She dies in his hands after proclaiming her love for him, along with one last apology. •
Lee Sung-jae as Jo Gwan-woong :A villainous nobleman. He lusted after Seo-hwa, then framed and killed her father, destroying many lives. He is now the mastermind behind a string of murders and a traitorous plan against Joseon, and he hunts down Kang-chi. •
Um Hyo-sup as Park Mu-sol :A just and righteous nobleman, Lord Park is beloved by his countrymen and is the father of Tae-seo and Chung-jo. When he finds the orphaned baby Kang-chi inside a basket floating in a river, he takes him in and becomes his surrogate father. •
Jo Sung-ha as Dam Pyeong-joon :A former soldier and now a martial arts master. Yeo-wool's father. :He's the one who leads the soldiers to Wol-ryung's residence since he deems the spirit too dangerous to be left alive. Due to Wol-ryung not fighting back, he manages to strike the spirit, dealing heavy injuries and 'killing' him. :He believes himself to be a part reason of Wol-ryung has turned into a demon and wants to stop the massacre however possible. :Strong ally of Admiral Sun-sin and tough enemy to Gwan-woong after learning of his villainous actions. •
Jung Hye-young as Chun Soo-ryun – The head
gisaeng. •
Yoo Dong-geun as
Yi Sun-sin – A patriotic naval commander with secret plans for building
turtle ships that could aid in fighting against invading Japanese warships. •
Kim Hee-won as So-jung – A Buddhist monk who was Wol-ryung's friend and now watches over Kang-chi. • Lee Do-kyung as Teacher Gong-dal – A wise old teacher at Master Dam's martial arts school. •
Jo Jae-yoon as Ma Bong-chul – A local gangster whose life is spared by Kang-chi, and becomes loyal to him. • Kim Dong-kyun as Choi – Lord Park's servant and Kang-chi's adoptive father. •
Jin Kyung as Yeo-joo – Yeo-wool's teacher in domestic skills, who has a crush on Gon. •
Kim Ki-bang as Eok-man – Kang-chi's friend. • Kim Sung-hoon as Wol-dae – Jo Gwan-woong's chief minion. • Son Ga-young as Wol-sun – A gisaeng who becomes jealous of Chung-jo, bullying and sabotaging her. •
Kim Hee-jung as Lady Yoon – Mu-sol's wife who resents Kang-chi. •
David Lee McInnis as Kageshima • Song Young-kyu as Pil-mok – Seo-hwa's assistant. • Park Joo-hyung as Han Noh • Nam Hyun-joo as chief maid at the gibang •
Lee David as Yoon Jung-yoon – Seo-hwa's younger brother (ep 1) •
Kim Bo-mi as Dam – Seo-hwa's maid (ep 1) ==Original soundtrack==