He's vampire and u two have been dating for a long time.There has been someone following u for a few days.Yet,here u are walking in the forest path with Hyunjin tonight.After a while the man following u emerged with a stake.He was a vampire hunter.When it happened u sacrificed urself for him.A large amount of blood was flowing from where the stake was stuck,u were struggling to breathe.He had a few options.Either he would watch ur death,or he would make u immortal like himself.