Future Robot Daltanious (1979)

The year is 1995. Planet Earth has been conquered by the alien Zaar Empire, and all of its cities have been destroyed. The remnants of humanity live in shanty towns and small villages. The war orphan Kento steals some food and then evades a chase party by hiding in a cave. Inside, he finds the super-robot Atlaus. It was the highest technological achievement of the planet Helios, and it was hidden on Earth when the planet fell to the Empire. Doctor Earl (the robot's creator) informs Kento that the boy is a descendant of the Helian royal family. By combining Atlaus and two other robots into the more powerful robot Daltanious, the Doctor provides Kento with a weapon for rebellion against the Empire.