Who is Korean schoolteacher from Lost Names: Scenes from a Korean Boyhood and what is their importance?

Korean schoolteacher defends the new boy from the Japanese teacher who hits and abuses him. The Korean teacher has a black belt in martial arts and throws the Japanese teacher on the ground and against the wall. He becomes a hero to the boy and his friends but tells the grandfather he is leaving for Manchuria. He arrives in Manchuria but later travels to Mongolia where the Soviet soldiers claim he is a Japanese spy and kill him.