honey_boo:
Itaewon Class
it's interesting example, not 100% what was asked, but guy loves girl very long time, she could have him but never tried and he didn't pushed he just said to her he loves her time after time. wouldn't say she was runing after him or really regreted after finely he moved on, but she liked him for sure, so I couldn't understand what she was waiting for... on the second hand we have girl who loves that guy and waits
I would add what wasn't mentioned:
Boys Over Flowers I know it's cliche and everything, but it's exactly what you described and not some second characters or while 1-2 episode, FL loved SML but he loved another, he starts falling with her when she starts moving on, though he isn't ML he is equally main and had more conection with FL, drama directly said he was her soulmate...
Can We Get Married? second couple 100%
Emergency Couple not exactly though they were married and he brock up with her now they meet again she is moved on even likes another but he starts falling again
Cunning Single Lady kind of same (ex married couple)
One More Time - not what you described but I'm sure you will like it, it's really good and diferent drama, not usual cliche romance, very realistic relationship and love, real life love, and "he values her, feels strong emotions, when it's late" thing.
Girls' Generation 1979 - what you described though I think second couples story is better, overall really good drama, with reply 1988 vibe.
btw if you haven't seen Reply 1988 it's one of greatest kdramas, + there is something similar situation, if you haven't seen it I really recommend also I recommend not to read hidden text, it's not very spoilery but at some point of drama you might remember it and guess who is the husband when this drama was most unpredicted, I mean they kept secret almost till the end and it added interest to watching it guy loved girl for long time but didn't acted and other guy acted... and he understands it's not fate or something, it was his fault, and we viewers see what's rare in kdramas - it wasn't like she was destined to one of them no matter what, or she was deeply in love, she was young and ready to love... we do our fates and our actions... it's so real but rare in kdramas... p.s. I shipped the guy who gets the girl )))
Perfect Crime - kind of that situations what you want, there are several main couples/relationships between 4 main character and thins 1-2 situation has that vibe. it's good drama, I'm not jdrama fan but I really liked it
When I Was the Most Beautiful GREAT drama, mature, not cliche and not predictable, interesting till the end and fireworks of raw emotions. about your request he loved her but it's difficult, it's so much more and he understands more when she after all moves on, but this description isn't accurate because this is't simple story maybe it's not what u described but this drama and relationships are soo reach, I'm sure you should try.
More Than Friend - haven't seen yet but as I know something like that