The voiceover was in fact his inner monologue; he seemed to think more than the average child, at first just a little bit, and then gradually more and more.
The child was named "Tai", which in this world was the name of a metal.
His father was a Smelting Worker in the smelting district, his mother was a Smelting Worker, and so was his grandfather; it seemed to be some kind of forced setting. They didn't know why the world was like this, only that it had always been this way, and that what they were doing was something people had been doing since ancient times, and that they would continue to do so from now on.
There was no need for change, because this was good; everyone had their own "place", which should not be trespassed, and one should not step beyond one's own setting.
The beginning of the movie was bland and oppressive, but the "Boundary Wall" at the edge of the horizon made the audience feel somewhat suffocated.
