on one hand, i agree w other opinions that yido shouldve told sejin, on the other, i don't think sejin shouldve been told bc w how he is rn, he wouldve tried hard to save his fam.
what i do know is that sejin needs to process everything properly, and maybe ido couldve contacted a professional to ask for advice. i feel affinity w sejin as i also grew up in a toxic abusive environment, and like sejin, i knew that things shouldnt be the way they are. the thing is, knowing and processing the experience are different things. sejin knows what his fam is doing but has always repressed it within himself/never processed it. idk if this manhwa is going the realistic route, but there's a pre-processing moment where everything that's happened is kinda buffering or loading in your head, then there's the main part of processing and thats where u fall apart.
in my opinion, ido shouldve done everything to kickstart the pre-processing part and be there for sejin for the main processing part. then when sejin's kinda ok, thats when he shouldve done his plan for sejin's fam's company. realistically, w how ido did things, sejins going to go back to his fam (worse, his father) bc the attachment is still strong. saw a lot of abused people do this in real life when they were forcibly removed from that situation and they werent actually ready to move on. idk how it'll play out here tho.
bottom line is, abuse, esp for the victim, is complex.