Probably the most pervasive theme in "The Kite Runner" is that of guilt. Chapter 12 contains evidence for that guilt. Amir's guilt keeps him from revealing his sin to Soraya. He also decides to go to America because "America was a place to bury my memories". Throughout the novel Amir is "running" from his pain and guilt.
Another theme in the novel is the role of gender in different cultures. At the end of chapter 12, Amir is aware of the double standard that exists for women in his culture.