Nobita ends up finding a destructive robot scouting Earth for an alien invasion. Now Doraemon and the gang must save earth from the evil invaders!

Our heroes learn of an invasion of the earth by a robot army and join forces to fight back against the enemy. After Nobita takes home a robot's leg and a blue sphere found at the North Pole, mysterious parts start falling on his house. Doraemon and Nobita assemble the parts to complete a giant robot, but then a young girl named Riruru appears who claims to be its owner.