The beginning truly grips you and you feel for each and every character so much that you can't stop watching, but especially Hye Joon. We've all at some point been in the situation where it feels like the entire universe is telling you to quit. But, HJ is stronger than most of us - he doesn't quit, he persists, he cries, he gets over it, he succeeds.

And then it's all downhill from there. There was no personal struggle left for the writers to use, I guess, so they brought in side characters that served no other purpose, but to cause conflict. Other than HJ, they were all one-dimensional, and simply did what they did, cause....reasons, I guess.

Jung Ha was clumsy. Hae Hyo was rich. HJ's ex was evil. His mother was a housekeeper. His father played favourites with his kids. The grandpa was a burden. Min Jae was a saint. JH's mother only existed to make her cry. Literally everyone character had a one-word-personality.

The ending, however, was what really sealed this show's fate of low ratings. I don't know how we went from communicating about issues and finding solace in each other, to hiding, lying and avoiding, but I do know that I hate "breaking up only to get back together after 3 years" trope even more than I hate Subway product placement.
And I really hate Subway product placement.