Responses

yes it is a common in a plot to create a flashback or explanation as a form of sympathy or closure out of one person after they went thru something bad. This called Falling action where the plot is trying to tidy it loose ends. From this it's clear that Joowon is the main character, soon it will reach to conclusions.
Hear me out
I think the author is giving us these flashbacks to justify and explain why joowon treated haesoo the way he did. In the beginning when the author was explaining their relationship they made joowon look like a completely emotionless bastard that only wanted to keep haesoo to himself. As you can see now he wasn't treated that good by his parents even as a child so that might have been what caused his possessiveness towards haesoo. Also in some of the previous chapters you can tell that he had genuine feeling for Haesoo and even wanted to propose.
Haesoo at first had only stayed with Taku to get Joowon and himself to lose him feeling for his parents sake. I mean i think we could all tell that at some point Haesoo was in love with Joowon. My point being we are still not completely sure of his feelings towards Taku though is they are just to help him forget about Joowon or if they are real.
This is just what i kinda realized as i was reading this chapter.
Of course this is just a prediction or whatever idk what happens i haven' t even read the raws so, don't come for me.
╮( ̄▽ ̄)╭