Joohyun has always been able to see them ever since young. The demons would disguise themselves as humans and walk around in daylight interacting with humans but young Joohyun was sure as hell what she saw was not human. 

She would try to avoid these things as much as she can so as to not bring trouble to herself. But, that was only until she turned eighteen because at the age of eighteen, the Church of The Seven Virtues have found her and she had found them.