What curse they are talking abt.. ?

I think its just a "curse" like blaming on someone for their missfortune, when on this case sungjae become their "curse", so they blame him for everything, even his tattoo was getting blamed as well, which is didnt make sense at all, or maybe her mom curse the "father" because i assume he was the one who killed sungjae father, i dont know maybe because ive watch and read a lot of yakuza movie and books lol