Wait hes dead?
(SPOILER SPOILER: if u don't get much of the context)
Yeah. even before the flashback it was revealed that seo-in was adopted just to replace the demon bitch of a brother cuz he got/ was terminally ill or sum shit.
I thought it was to replace the dead twin?
yes! jaewon's twin died and seo-in was adopted to replace him. in the 1st season, we see seo-in visit a cemetery with jaewon's name written on headstone. it is also further implied in the next scene when he has dinner with his adopted family and they ostracise him.
That backstory explains so much. Immaculate pacing. I kinda get how seo-in acts the way he does.
Thank god the bitchass brother is dead.