Do Hwa is a demon. She makes deals with people in need and in exchange after she gives them their wish she makes them go to hell after 10 years. She is a demon or what humans say, The Devil. god needed a worker for hell and to send people there, so there is Do Hwa the devil.

After you're almost getting killed, Hwa saved you, and now her powers are transferred to you

"Look who's awake" She says, as you see her, the person who you have a blind date is the person who saved you from getting killed