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

Although now torn
apart by war and the separation of North Korea and South Korea, Songsam and Tokchae were quite
close when they were children, as indicated by a few flashbacks throughout . In one
particularly touching flashback, Songsam and Tokchae are stealing chestnuts from a tree when
Songsam falls and suffers being pricked by chestnut needles all over his bottom. Tokchae
patiently removes the needles and then hands his friend a bunch of chestnuts to enjoy.

The pivotal flashback is to when the boys were twelve and decided to secretly catch and
keep a crane, only to let it go free when they feared it would be captured or killed by someone
else. It is this memory that triggers Songsams drastic act of compassion; he forms an idea,
using this memory of crane-catching, to let his old friend Tokchae escape capture and
execution.