I think a main theme of this story is the power of friendship.
The story begins with Tokchae being taken prisoner. He is being moved to a new location, and Songsam decides to be the escort. The two men used to be very close friends. As children, Songsam and Tokchae were inseparable. They got into trouble together, shared food together, etc.
Plucking out those needles hurt so much that he could not keep tears from welling up in his eyes. Tokchae produced a fistful of chestnuts from his pocket and thrust them into Songsam’s.
It has been many years since the two characters have seen each other, and they are now on opposite sides of an ideological conflict. When the story begins, Songsam wrestles with how to talk to his former friend. The conversation that eventually ensues has some anger and heat to it. Songsam is upset that his friend could fight for the other side of the conflict, and Songsam wants to know why. Tokchae explains that he wasn't willing to run and leave his family.
The entire conversation is woven with childhood memories of the two men. One of those memories is about the time that the two men caught a crane together. They thought they were going to get into big trouble, so they let it go free. Moments after Songsam remembers this part of their friendship, he turns to Tokchae and suggests that they have a crane hunt right then and there. Tokchae doesn't understand what is happening at first, but then he realizes that Songsam is giving him the chance to escape like the crane instead of being executed.
Despite being on opposite sides of a brutal conflict, the men's friendship runs deeper than the conflict, which shows just how powerful friendship can be.