Dramas with male characters that have broken up with girlfriend or lost their fiancé or wife and they can't get over them. 

It can be the lead guy or secondary guy character. 

They reject the girl that loves them but than opens up to her. 

Something like the secondary couple in BOYS OVER FLOWERS Or the drama INNOCENT MAN. 

Man to Man
We Broke Up
Goong I watched and I agree meets my requests. 
Man to man he didn't have a first love he couldn't forget. 
We broke up they got back together. 
I mean a new lady not the same ex. I don't like second chances its to predictable. 
But thank you girls. 
Actually, in Man to Man, Woon Gwang couldn't forget his fiance, Mi Eun after she left him for another man. But nevermind, since you already watched it. 
Another Oh haeyoung
my Name is Kim samsoon
lovers in prague
What planet are You From
scholar who walks at Night
my girl
Gu family Book
My Lovely girl
you are the best lee soonshin
fight my way
golden bride
masters sun
Immutable law of first love
smile you
ugly alert
Rooftop prince
cyrano dating agency
prime minister and i
triple

Guy with only one-sided love with some girl and they cant forget said girl:
delightful girl chunhyang
full house
Oh My ghostess
jejudo gatsby
Heartstrings
my gf is a gumiho

non-korean dramas:
Sunny happiness
Loving never forgetting
drunken to love you
Love Around
Fated to love You
please Love the Useless me
last cinderella
go princess go
H2

@polarizing omg you are right, sorry. 
Fated to Love You
Goodbye Mr. Black
Goong
Summer Nude
Another Miss Oh