There is no real main story I think. "Kiss me liar" is the first story the author released for this universe, probably one of the reason was that the MC is a korean, at least I think that was a factor.
And earlier this year she said "Desire me if you can" was the first she came up with, but released it 10 years later -this year... .
The author made clear very early that she was writing two series for this universe "...if you can" for the Miller family consisting of 6 stories and "Kiss me...." also consisting of 6 stories. Even the titles were known years ago. And she also worte a few titles not being part of those series.
If you go by release "Kiss me liar" was the first, and after that "Kiss me if you can".
If you go chronologically. "Kiss me liar", "Kiss me if you can", and "Run away if you can" take place around the same time, but "Eat me up if you can" and "Lick me up if you" can would come before. For the Miller you actually have 3 generations.
For manhwa's only "Kiss me liar" and "Kiss me if you can" were adapted.
If you want to read Kiss me liar, be warned, most really don't like the dynamics, it's toxic.
Keith is a pretty notorious trash ML and Yeonwoo lacks backbone most of the time when it comes to Keith.

Is this worth reading if I dropped the main story...? This looks like a better story......... is it?