Honestly, Kim Go-eun and Jung Hae-in are the main reason I decided to watch this movie. They truly did not disappoint. They had great chemistry, facial expressions and they made it all seem real. I feel this movie would not have been a hit without these two main leads.
All in all, I'm not really a huge fun of Korean movies because I feel they are rushed (in comparison to dramas) and I felt this was rushed as well. There are some story lines I would have loved to know more about (the accident), if he eventually made up with his friends, to name but a few. But I totally understand it becomes quite difficult with movies since you cannot have a whole 2 hour movie.
I'd suggest it to everyone who is a fan of Kim Go-eun and Jung Hae-in as they portray great acting skills, as always. I'd re-watch it again, for the same reasons, just to see their chemistry ;)
The music used kind of blended well with the movie and I mostly enjoyed Fix You by Cold Play.