A symbolic feature of losing innocence can be the kite. The last time Amir and Hassan flew a kite was the last time they were both innocent. So the kite might represent the good before the bad. It represents innocence before it is taken in the novel. But it also represents how Hassan lost his innocence by being raped because he was trying to save the kite for Amir.
“I actually aspired to cowardice, because the alternative, the real reason I was running, was that Assef was right: Nothing was free in this world. Maybe Hassan was the price I had to pay, the lamb I had to slay, to win Baba”, Amir explains just after seeing Assef rape Hassan. Rather than intervening, he runs away. He justifies his doing by saying that Hassan was to be sacrificed
“I actually aspired to cowardice, because the alternative, the real reason I was running, was that Assef was right: Nothing was free in this world. Maybe Hassan was the price I had to pay, the lamb I had to slay, to win Baba”, Amir explains just after seeing Assef rape Hassan. Rather than intervening, he runs away. He justifies his doing by saying that Hassan was to be sacrificed