When Miles, the Colonel, and Takumi realize the reasoning for Alaska's death. She remembered that it was the anniversary of her mother's death. She wanted to go to her grave but on the way there she either committed suicide or it was just a fatal accident that took her life.
When the Colonel and Miles decided to go back to the place where Alaska died, they started to feel very emotional. They cried together and tried to think of Alaska and what she would have wanted.
The semester is coming to a close and Miles hasn't finished the final for the Old Man. So he sits down to write it. He writes about a many realizations like, he thought that the way out of the labyrinth was to ignore it, he will forget Alaska and she will forgive him for it, and he wishes he could've gave Alaska hope to not commit suicide.