The Devil Garon

One night, two meteorites from space fell down to Earth. The larger of the two was brought to the research institute headed by Prof. Tawara of Tokyo University. That meteor was discovered to be a giant robot named Garon.

The other meteor landed in a human village. In it was a small child named Pikku. He is taken in by the teacher of the village school, and raised as a human boy.

What exactly is the connection between Garon and Pikku, and why were they sent to Earth?