In Cranes by Hwang Sun-won, what was Songsam's relationship with Tokchae like when they were children?

When Tokchae and Songsam were children, they were childhood friends with each other. 

The story gives some small details from the characters' pasts that indicate that the two men were fairly close friends.  For example, Songsam initially thinks that offering Tokchae a cigarette is bad timing, but then he remembers that Tokchae and he shared stuff with each other when they were children.

Then suddenly he thought that Tok-chae, too, must want a puff. He...

When Tokchae and Songsam were children, they were childhood friends with each other. 

The story gives some small details from the characters' pasts that indicate that the two men were fairly close friends.  For example, Songsam initially thinks that offering Tokchae a cigarette is bad timing, but then he remembers that Tokchae and he shared stuff with each other when they were children.

Then suddenly he thought that Tok-chae, too, must want a puff. He thought of the days when they used to share dried gourd leaves behind walls, hidden from the adults.

Near the story's conclusion, Tokchae and Songsam arrive at a field together.  The reader is told that this is the same field where the two men captured and freed a crane together as young boys.  

Once, when Song-sam and Tok-chae were about twelve, they had set a trap here, without the knowledge of the adults, and had caught a crane, a Tanjong crane.

Tokchae believes that he is about to be executed in this very same field, but because of their childhood bond, Songsam decides to let Tokchae run away.  Just as the two men let the crane go free as boys, Songsam is now letting Tokchae go free as well.