Guys this is a note from the author:
If everyone agrees with a little spoiler ... Part 2 will focus on Huilin. We'll explore her past with Jaehee and learn things like why they broke up. We will learn more about Zhu Huilin as a person. By the way ... Just because Sulhwa broke up with Jaehee, that doesn't mean they lived happily ever after! "Relationships can be complicated. It doesn't take much to break up a couple, after all! Stay tuned for some doom and destruction in Part 2! (Mwahaha) On a side note, Huilin has happier days for ahead (haha).
End of the note.
Hopefully Sulhwa is the one who leaves Jaehee and not vice versa, to go with Huilin.
Personally, I am team sulhwa but it's so obvious that the author's favorite characther is Huillin. And I believe that difficult times are ahead but if the same author says that relationships are EASY to BREAK then I don't see much future for jaheexhuillin's relationship neather.