Beyond the walls

For 100 years, all of mankind has lived behind the city walls. Levi and Erwin are forced beyond their safety, left to be killed by the titans. As not being able to return to the city they just head through the woods hoping to survive together as long as possible. They expect death soon, until they meet someone who has lived outside the city her entire life, never even hearing of the walls. She hasn't been living alone either, she is surrounded by people unprotected from the walls and protected from the titans.