At the beginning of the show Yoon Jae Gook says something like "let's love while we are breaking up"...the phrase should have been "let's struggle and suffer by ourselves while breaking up". They had more chemestry in the first episodes while they were not together rather then when they're a couple. They never really face their problems as a team, but they seem to leave one another out of their struggles, like they need to face everything on their own.
And the plot is so frustrating! All the world is against them and their love in a way that is unreasonably fierce. Maybe the cultural gap between Western and Eastern culture makes it hard for me to understand completely why they act like this, but only in Itaewon Class I found a similar harshness. I mean, ok, ok being mean at the beginning, but at a certain point it all becomes unbearable and unjustifiable.
Thank God we had the secondary couple lightening up the scene.
Anyway, despite many reviews stating the contrary, I found the acting of Song Hye Kyo very good and credible most of the time, above all when portraying both the happy and the sad moments of the relationship with her friends and family.