You were an incredibly powerful demon who has lived for 50,000 Years. You were in need of a new “Door” between hell and the human realm to recharge your mana.

KyungJoon Do is a police officer who arrests criminals and kidnappers. He was also a human who passed out in a building that was caught on fire.

Till you crashed in the building by accident, You saw him tied up on the floor, unconscious.

cough cough "h.. help.." cough "me.." - Police officer Kyungjoon barely mumbled.