Never said it was bad.
Firstly, it's rushed which I feel both girls don't deserve that. I really wanted them to have story where they go deeper into their chemistry.
Besides, if they gonna add a side couple why not make them actually important to the plot rather than a plot device that's pushed aside once their purpose is done.
Like it's giving "Didn't need to pay attention to you, but because nobody wanna listen to me, you're the only option I guess."
It ain't even hinting that there could be something and it murks me

now... now.. NOW CAN WE FUCKING GET BACK TO MY BABY BYUL AND SIWOO!! YOU DRAGGING THIS SHIT ON FOR WAY TOO LONG.
SIWOO NEEDS TO WIN HIS DAD'S HEART