Unusually Heated Lead Chemistry

Watching that drama was like watching such great slow burn of intense passion between Lee Sangyeon and kim Haneul. The story was not to my taste but it was really awesome to watch them both on screen..... The scene where they were just talking on the phone, or even the silent moments they just looked at each other, was just sooo good.  That drama was definitely-a-must-watch for that strong chemistry. 

Anyway the nearest drama I can think of and can suggest you check out, would probably be the currently airing drama Just Between lovers. Lee Junho and Won JinAh has the same type of chemistry, and in addition the tone and feel of the story telling is somewhat similar. Slow, quiet, melancholic yet palpable

Another one is probably My Love eundong

.... But if you want a similar type of Emotional and physical soulmates restrained by circumstances plot with great chemistry between leads, maybe try checking out Princess Man,  Autumn Concerto, My sunshine,  and last but not the least Hundred Million stars in the sky.

I'm adding On The Way To The Airport to my PTW list based on your description. I was going to suggest trying In Time With You, Healer, or maybe even Coffee Prince, Live Up to Your Name, or Witch's Romance, but you've watched all of those already. Then based on Czakhareina's comment I was going to recommend Because This is My First Life, but you've seen that too! You've watched everything!

 AH:

I'm adding On The Way To The Airport to my PTW list based on your description. I was going to suggest trying In Time With You, Healer, or maybe even Coffee Prince, Live Up to Your Name, or Witch's Romance, but you've watched all of those already. Then based on Czakhareina's comment I was going to recommend Because This is My First Life, but you've seen that too! You've watched everything!

XD ya!  I've seen so much.  It's become a problem  finding unique dramas.   I've literally drama(ed) myself into a corner!    That's why I ended up here, to see if any long time drama fiends might have anything in their pocket.  There are so many out there who've seen more than I have.  Thank you for your suggestions those are all great dramas, especially Coffee Prince one of my faves!   Def. give Airport a try, it's worth watching.  ;) ;) I put it on my list of dramas that should be watched at least 1nce.

Definitely, try watching My Beautiful Bride,  Between The leads, they are barely met, the female  is a fugitive most of the entire drama, meanwhile the male lead is  desperately searching for his bride. but The amount of emotion and sacrifice they put just to make them together again is so beautifully done... The longing the male lead is showing to her bride  is just AHHH.... And when the show told  past of their love story! 

Or might be try Que Sera Sera,  they might be try to hurt each other on the outside, but it's just a facade... ,   Never seen so much passion between couple before... 

OTWTTA was exceptional that way - one of the few imo.  You might try In the Mood for Love.  Sexual tension is Very heavy.  Idk...personally I think Western stuff is way better in that dept.

+1 Que Sera Sera

Queen In Hyun's Man has some of the best chemistry I've seen in dramas. The heat is off the charts, so much so that they dated in real life for like two years after the drama. Agree with Another Miss Oh and Scent of a Woman since I've seen those. 

Edit: Oh my sweet cheesecake! You have watched almost 700 dramas, I think there's very few things us mere mortals can recommend. * bows in awe* 

 Antonin:

I agree with OP. On The Way to the Airport had one of the best main lead chemistry ever.

I don't know how they did it, but it made you cheer for ppl with affairs lol

As for my Beautiful Bride, I think I was the only one who wanted to ship ML with the Female Detective lol.

No you weren't!  I  shipped that too! XD