this is the best kdrama i ever seen most of you are saying that how he was alive in the the last scene , if you watch the last episode carefully jung jee tae was having conversation with jung hye sung when he revealed the that park ji sang can live without heart according to his research and when park ji sang and director were fighting director stab park jisang in his heart so i think when he was watchimg sunrise with yu rita he was healing due to his mutated gene he fainted . and at last scene they both went to see that girl whom he saved in war .