The labor camp
Life in the labor camp is grim. The industrial complex is all that shapes their society, and the government pays unfair wages, basically enslaving their own people. The labor camp is shown to be an unsafe place, and Shin is only 10 when he begins to work the coal mines, a historically dangerous and painful job with serious health risks. Their work is extreme and their workdays are long and without break, and when they go home, the government doesn't give them enough food as payment for them to survive.
Competition
As mentioned, the government pays food stipends that are insufficient. This turns even the family home into a vicious competition. The competition is violent and sometimes hateful, turning sons against their own mother. For Shin, this tension existed the whole time, but when one day he sees his mother giving food to his brother, he cannot handle it emotionally and he decides to betray them. He himself is competitive and wants to survive.
Escape
Very quickly, the novel takes on an imagery of escape and desire for escape. The method by which Shin betrays his mother and brother is to tell a guard of their escape plans. He is imprisoned for this. He desires escape from jail. He and his father watch alongside the entire camp as the mother and brother are executed and humiliated for attempting escape, and then Shin decides to escape with the subject of his government spying job. He escapes over Park's dead body.
Life as a witness
In the moment, these stories are merely sublime horrors that Shin cannot understand. He escapes into a new career as a witness of those horrors, and he becomes like a surviving martyr. In this new life, he has survivor's guilt and impostor syndrome, because he knows the truth about his own guilt. In the novel, however, this is all still part of the witness imagery, because through his corruption, the reader witnesses a deeper truth about Korea.
