Introduction MUST READ TO UNDERSTAND STORY

This is somewhat of a sequel to Purple Flames but you can read it without reading Purple Flames as it doesn't have a whole lot to do with Purple Flames other than the reason Jungkook and Hyunjin watch over her. The backstory will be explained during the story as well when they explain it to Promise so you can start by only reading this book if you want.
Hyunjin (an angel) and Jungkook (a vampire) have watched over Promise in an orphanage until she turned 17 and finally got to leave for a day without being supervised by anyone from the orphanage. They acted on impulse and introduced themselves to her. What happens after they spend some hours together and it's time for Promise to go back and not see them anymore? Read to find out. :)