Long story short: There is no better K-drama out there.
My mom and I plan to watch it for the second time together soon. This was the very first K-drama we watched after discovering K-Pop/EXO. We watched it years ago and still we find ourselves talking about this drama and discussing the characters from time to time. You become so emotionally attached to it all, the good and the bad. You won't believe a K-drama this good exists until you see it for yourself.
Don't forget to keep a box of tissues close by.