
Love this, i had already kind of imagined that they would have been blood related, bc it reminded of the plot of "Jaa, Kimi no Kawari ni Korosou ka?", but still was a nice touch.
I actually liked the character of Gangsae (the blonde one), bc he actually felt human, many stories of revenge and bullying the bullies have a simple mind, they just want to hurt, while Gangsae actually DOES care about his friendship and happy memories, not to mention his father's business (except that Sayin guy, since he was really just a goofer).
I liked Namsoo/Sun, but in the after notes the author said he's something like a sociopath, but honestly, he felt to me more like in the autistic spectrum, i mean, i'm not a specialist, but from what i know, people with psychopathy are usually social, while our dear Sun doesn't focus on anything/anyone except Sungman.

i think it's possible to have both because namsoo/sun doesn't feel any guilt which is a symptom of aspd and he also shows signs of autism
however i think he's more of a psychopath than a sociopath because sociopaths are usually impulsive and aggressive while psychopaths are calm and collected and can adjust their behavior whenever they wish
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTDJ32_7Il5eqe9MZ58ZCxaxGrjRTOBE-r-NnNtGtqTficB7kr6Mtd11zw&s=10
he's also very calculative, he planned how he will avenge his brother. i want to point out how he checked jangsoo's strength first and thought of a way to beat him. namsoo knows he won't win in a physical battle between him and jangsoo so he put drugs in his drink instead and let jangsoo ruin his life himself, like a domino. plus, luring geumsoo by using his brother? yeah even though he only cares about him he still used him as a bait (⊙…⊙ ) a psychopath behavior ig
That was cute