Kokdu: an underworld god who has been cursed to lead the deceased in the afterlife after angering the Creator, and has to enter a human body that looks just like him to carry out the murders of immoral people.
Do Jin U: a successful surgeon and Gye Jeol's fellow hospital worker, who is possessed by Kokdu.
O Hyeon: Seol Hui's love,r who was cursed by the Creator to become Kokdu.
(Source: Wikipedia)
