After finished episode 9, I was disappointed at the ending. Then I realized something more into it and that make this series is even cooler. The beginning of every episodes, I saw everyone went out at the beach and they look happy. Doona met Wong jun at the pink field. He was smiling and he wore the same outfit in the ending when they walked opposite way. So I assume that they are in some kind of relationship. It is a happy ending. I would not believe it if he keeps waiting without hearing anything from her nor they come back to be together and she announce their relationship. This is a realistic ending.