In a world where giants that eat humans roam freely, people have surrounded their cities with massive, strong walls to protect what remains of the human race from extinction. This has confined their freedom, limiting them to living within these walls and preventing them from going outside. However, the unexpected appearance of massive giants that breach the great walls has disrupted the safety the humans have enjoyed for decades. This sparks a battle for our heroes against the giants to regain their freedom, during which they uncover many secrets.