I think this is the answer to your question I don't know.
The way Martin change during the story, He learns to value his heritage.
Evidence: Martin’s predecessors had placed their sacred possessions in the medicine bag. After the death of martin's grandfather, he returns to the rosebud reservation and carries on the tradition. So basically the medicine bag is about a boy called martin that his ancestors are Native Americans. So now he loves his grandpa and says that he is amazing. He learned that he must not be embarrassed by his cultures or traditions. Before the grandpa died he gave him the medicine bag.
