Gaba Kawa (japanese)

The book I am reading this week and last week is called Gaba Kawa. The book is about a girl named Rara who is a demon who came into this world to wreck humans (demons call them mortals) and anything they can do to make them to have bad luck so she had to start a life as a mortal but actually a demon. So one day, when she was going to school she heard that a famous demon is in this school and she has to try to beat him at giving people bad luck but she actually fell in love with a mortal named Retsu. And he also likes her too, but it a demon falls in love with a mortal, then she or he will diasappear! So the only way for her not to disappear is to kill him, but she would never do that! What should she do?