i really love dramas with side couple along with main couple. these are the dramas that i have already watched.
boys over flowers- awesome side couple
perfect couple(c-drama)
just you(c-drama) there were many side couples in this
pretty li hui zhen( the side couple's romance was very nice)
legend of the blue sea
autumns concerto( well it kinda looked like the second male lead ended up with the girl who was his friend)
it can also be about two couples( as like in goblin) but they should end up together. so pls recommend me any drama with that kind.