(spoilers up to ch 25)
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1. no, they haven't verbally labelled themselves, but you can say they're in the dating phase 'cause everyone but sugyeom sees it that way. i dislike the word fwb used to describe them 'cause that would mean they lack any romantic aspect about their relationship
2. no, he was talking about setting a trap for the h100 dealers. the 'incident' you're thinking of seems to be the drug scandal party, which happened in a hotel and not favela. the trap sm was talking about was setting the flashing lights at favela to catch the dealers attention (ch17), which jy happened to get caught up in and fainted (ch2). and yeah, most readers think sm fell for jy at first sight.
3. yeju doesn't seems suspicious to me. she was originally part of sunshine ent and got merged into dive. she was the one who scouted jy (ch25) and probably one of the few ppl that know about jy's situation. in ch6, she and sugyeom agreed that "rather than letting that jerk (jun? dive?) jerk us around forever, i don't think it's a bad idea to take a chance on this [collab]."
4. jun has connections to dive since we know his uncle works as div 1 director (yeju is div 2 director, you can check in the season 1 review for the chara chart). so it's probably a mix of both. jy probably got verbally abused by those on that side of the company

- do seungmin and jaeyoung a couple? do they establish the relationship or is it fwb?
- if seungmin said that he carefully planning a trap from the moment they met at fravela, does he know abt the incident? but from what he's been researching in the newest chapters, he still learning about jaeyoung? so is it a love from first sight?
-why jaeyoung manager i forgot her name felt so off? is she apart of being the shady junkie?
-who exactly ruining dream boy future? junhyun or that dive director??? im so confused
sorry for soo many questions, i reread it so many times that i actually cannot understand it in my head.. pls explain to me and sorry again