beta
my guess is like those two are like siblings or even twins (at least related), and shin yooyung was the bad guy and kwon was actually married to the white haired guy, WHICH is the guy that "possessed" shin yooyung's body (which is why he doesn't remember people), but this guess is difficult to tie ends such as why is he violent with kwon sometimes (idk sharing a body or wtv), could be something similar tho