Its a trilogy with the 1st one being choice of choice (Lee Han x Jung Ji-in)
Then the 2nd one comeback no choice but (Lee Hae Song x Choi Hong Seo) and this is the last one (Yoon Johoo x Song Hyunsoo)
They are all kinda main since it all stands on its own even if you dont read the other one but more info on some events if you do read them.
I personally like comeback a lot! But its emotionally the most taxing and angsty out of all i cried a lot. Dissolve is also still top of my fav as well as their dynamic is just so peak and Its more light hearted.
I havent read the choiche of choice but i see a lot of wholesome comments on it so I might try it and see!
That actually make me so happy you started on the novel!! ヾ(☆▽☆)
This author is def my fav their writing style is just so gooddd its almost like watching a movie in my head when reading them hehehe and feels like everything flow so well and not much cliche!! Same author with diamond dust too so no wonder they are just so good

Is this the main story and Choice of choices Ji-in's spin off or the other way around? Like this is the spin off of the second lead who wasnt chosen (this story's seme)? Asking because the other webtoon is older so im guessing that is the main story which unfortunately no translation team official or not has picked it up, i remember it was quite interesting