Why they are... SO CUTE.
Jang Su-ro lives in the slums of Korea with his three sons 963, Dog Nose and So-and-So, who just got out of prison. While So-and-So's loyalties to his mob boss and biological family are put to the test when he finds that his family's home is slated to be demolished by the mob's developers, the rest of the family's life is complicated with the arrival of Sun-yi, Jang's new girlfriend who annoys Dog Nose and attracts the affections of 963.
