1. Terminus Underground City

This city was built by humans to avoid the radiation disaster from the sun a hundred years ago. The city is described as similar to Hong Kong with a slight mix of India in the real world, with tall buildings and a very dense population. The underground city is constructed with iron frameworks that protect it, similar to a shelter.

2. Time

We are currently in the year 2230, and the disaster occurred in the year 2115.

3. Disaster

The disaster faced by humans is radiation from the sun. The inspiration I took from this, is imagining what would happen if the ozone layer of our Earth disappeared and solar radiation attacked us. I found some sources saying that if our ozone layer disappears, we will be prone to diseases like cancer. So, I took inspiration from that.

4. Surface Earth Research Expedition

This is a governmental organization for researching the surface of the Earth. Their task is to enable humans to live on the Earth's surface. This organization will be crucial later in the story, but it may not play a significant role in the beginning.