Just finished watching it and it was superb! Actor/Actress are Amazing especially Kim Go-Eun! The only griped I have is the overacting of In-Ah and the stalker arc. She is really good but it just exaggerated for me and the stalker, I prefer in the movie, it is more dark tone to it. About the ending, we have different opinion, some people don't like it and some wants more. Maybe the Webtoon is more compelling. But I didn't read it yet.
[SPOILERS]
Anyway the last scene when you see Hong Seol is still checking on her email, you will see the sadness on her face. Losing hope. The time she's walking out on her room, the Camera Dolly Shot to the Computer screen. Revealing on her Inbox , someone replied. It was Yoo Jung, if it was calling her name out. It is not a perfect / good ending, it was an open ending and I liked that.