I recommend 

• The fox's summer

• Cinderella & 4 knights

• Cheese in the trap

• Because it's my first life

• Oh my Venus

• The master's sun

 fanitha:

You're right about 20th century boy and girl, there's a secondary couple, sorry about that forgot about it. 

its okay, but im willing to check it out, thanks again

 dearlymissnina:
I recommend 

• The fox's summer

• Cinderella & 4 knights

• Cheese in the trap

• Because it's my first life

• Oh my Venus

• The master's sun

Thanks but I've already seen them but I was thinking of watching the master's sun again but forgot the name thank you for reminding me even though you didn't mean to...

I think you might like Doctors. Park shin hye is in a pretty strong role in it. :)

Your description kind of makes me think of Hwayugi. One main couple and nothing really breaks them apart despite many people trying. There isn't an ex-girlfriend per se, but there are a couple trying to be current ones. 

Maybe Kill Me, Heal Me would work? There is one couple and a woman from before who tries to wedge herself between the leads. 

 Linus:

Your description kind of makes me think of Hwayugi. One main couple and nothing really breaks them apart despite many people trying. There isn't an ex-girlfriend per se, but there are a couple trying to be current ones. 

Maybe Kill Me, Heal Me would work? There is one couple and a woman from before who tries to wedge herself between the leads. 

I've seen hwayugi and your right but towards the end they kind of do separate, and for kill me, heal me. I didn't like the fact that the ml had multiple personalities so I didn't check that out but thanks for the recs.