Unnamed Story Idea (Giants & Humans)

Okay, so the story is that humans are going down in the world. Slowly, the population has been decreasing. There is a safe place for humans called the Human Society. There are various safe places throughout the countries. Many people live in the Human Society, yet numbers are still going down. (Of course, people live on their own too, it's not unheard of.) The Human Society made a rule, only a few years ago, that the age limit to work is 10, though it used to be 12. They decided 10 year olds could be as hardworking and understanding as 12 year olds. That was about the time they told of the "friendly giants."No one dared to believe it. Those bloodthirsty monsters were willing to help them?! Finally, they started to believe it when the young children, more likely to accept the newcomers, got giant companions. Many people finally started to believe and hope, though they still didn't understand why they had to risk their lives when they had a safe haven where they couldn't be hurt by the giants.