If you want a short drama which you wanna finish early with good story, than this drama is a thumbs up. The story is quite good, small and decent. Each episodes last from 6 minutes to 12 minutes. So the epsiodes are small with good video quality, nice story and each episode that had a story focused on different casts of the dramas. Not so complicated & easy to understand, best thing is that you can complete it within a few hours and you will note feel bored any second while watching it. A few of the ost are good too with Exo in one of the ost, it made music a good experience.
It have 4 seasons, so i will suggest you to watch all four season together to have a better understanding as all seasons are somehow dependent on one another. It is a popular series as far i know about 500 million views it had got on youtube totally on all of its episodes.

Note - Th upcoming drama, Dear M starring NCt Jaehyun is also extracted from this drama. A few cast have been changed, but it is the part or extraction of this drama you can say. Still there are issues that if Dear M will release or not because of bully allegations on of the main cast. You should still finish this too in case if Dear. M airs you can watch that too.

All the best. Enjoy!