I think that our ml's brothet got the list from where he worked and had to quit because the list had something to do with illegal stuff . He then gave the list to piao the corrupt officer thinking he would do justice but ended up getting killed. All in all , I think the serial killer didn't kill his brother and that he is killing the people on the list. Just my theory. Ty for reading 😁
RED FLAG is what I think I'm looking for but in reality it's the character development that I'm after
