Who Are You: School 2015, Thats a veeery special drama if we're talking about OSTs, No Joking!! Every single OST of this drama is just awesome. The story is also very exciting from the very beginning to its last episodes.. you may find it a bit cliche in the first episode because of the bullying thing (tough it's only natural coz we're talking about a scholastic drama) but it will take a very different course than the usual after the 2nd ep,. i think... :D The drama's only flaw to me was its love story, i would've prefered if it stayed just a friendship relation instead.. anyway, the drama's very worth watching.
The Princess' Man.. "Korean's Romeo & Juliet".. i've never seen R&J's play nor completed its story before.. but from what I know about it, it's so similar to this drama.. not only about the story, but also about its uniqueness.. i'm not so into historical dramas but that one is somehow different, and it's one of the best kdramas i've watched so far.
One Litre Of Tears: That drama is a most! You have to definitely watch it.. and I advise you to download it because you'd want to rewatch it a few times ^^.
King2Hearts, Hmmm This one is really different, i've never seen another drama with such a plot. To me, it was the best drama of both Lee Seung Ki and Ha Ji Won (its main actors), their roles fitted them just perfectly.. And all the other characters were amazing. Its OSTs were also so good that I still listen to them from time to time. The only thing I couldn't and still dont understand about it is the title :D
I Remember You, I saw this on your plan to watch list 'n I advice you to make it your priority when you want to watch a new drama.
It's Okay, Thats Love: that one is unique as a different romance, unique strong main characters, unique mature discussions (btw, they are really mature, i mean, literally XD), and a unique plot of course.. and, again, great OSTs
Reply1997, Reply1994, Reply1988... Nothing to say, just make sure you watch these series in that order.
Just one last recommendation :D
Nine: Nine times time travel: Just watch it .. and make sure you concentrate 100% while watching it.. you'll need every single bit of concentration you have.
That's it, I hope you'd find time to watch all these dramas.