Nobita Nobi brings home a robot leg and a strange sphere found at the North Pole, and soon more parts start falling from the sky for him and Doraemon to assemble into a giant robot. A girl named Riruru arrives claiming the machine as her own, revealing it comes from Mechatopia, a distant planet where a professor's two humanoid creations turned against their maker's ideals and now plan to conquer Earth. Riruru was sent ahead as a spy, and as the invasion nears, Nobita and his friends have to decide whether to trust her. This 2011 film remakes the 1986 Doraemon movie Nobita and the Steel Troops.