Left overs. Trash. Loose ends. Scrap. That's what about 9% of the population was.
Well, 9.25% was the number before we were no longer allowed to search through the world's viral connection. The world population was at 8.3 billion, meaning 767,750,000 were left the last anyone could check. A tenth of our people left after the Furies had taken power.
The Furies. The three mysterious, hidden figures of power who we'd seen as our saviors. Despite their wretched name, they seemed to do only good. Clean energy, unextinction of species, world peace, all the good things we were supposed to wish for when we got our genie.
Then they flipped it just as fast. As soon as the desicion to name them as the fully powered leaders, a large fraction of all living humans were gone the next day. Then the same cut the next. Then the next.
It happened in various ways, but it actually all felt real the moment the lights turned off and didn't come back on.
Everything started in 2036. The pollution was so bad that the end of the world was predicted to be right around the corner. As complete panic set in around the world, the rich and important people were all gathered and placed on giant spaceships with enough resources and room to house generations of human beings. Before they left though, the government leaders fired As a result, most of the human population died off and earth was a complete wasteland. The little that survived started building local communities and trying to survive in the destroyed excuse of a planet.
On the disaster of a planet, creatures mutated and were born out of the nuclear chemicals; creating new species and monsters that hunted humans. While hundreds and hundreds of years passed, the monsters kept evolving and the people kept adapting while still trying to keep a sort of community. They didn't want to lose all of their humanity and become nothing more than animals that hunted the monsters: then they would truly be no better than the monsters themselves. So they stayed civil while still doing what it took to survive.