Why did Jonas leave the community? Did he miss his family, friends, the community, and his assignment? Who told Jonas to runway?

The Giver and Jonas make a plan for Jonas to run away and release all the stored memories into the community. By this point in the novel Jonas feels separate from the community. He has long since lost his affinity to anyone he grew up with, including his parents. His experience as Giver has put him into a whole new realm of thought and emotion.