In The Kite Runner, the impact of the journey can be measured in the emotional change that characters experience.
Hosseini's work shows how people change as a result of the journey they undertake. Baba changes when he and Amir move to America. He becomes more understanding towards his son and demonstrates greater compassion in his relationship with Amir. While these emotions were always there, they become more demonstrative as a result of the journey to America.
For his part, Amir changes when he undertakes the journey back to Afghanistan. Prior to his return to Afghanistan, Amir had to live with how he witnessed Hassan being abused. He was unable to acknowledge the depth of his relationship with Hassan. However, as a result of his journey, Amir changes. He is forced to confront Assef and take action in the name of his friend. When he was younger, these were situations where his weakness was exposed. His journey back to Afghanistan represents a “way to be good again.” Finally, the journey changes Sohrab. His life experiences massive change upon leaving to America. As a result of his journey, Sohrab learns to trust and be more open with people, in particular, Amir and Soraya.
In each of these situations, the impact of the journey is to initiate change within characters.