Ciel and Wolf are cousins, the only descendants of the Kjeld tribe in the world. The tribe was destroyed thousands of years ago. In the long history, they also found their own jobs, and the two immortal sisters started their new lives.
This world view is "Collapse Star Railroad", part of the history is fictitious, has nothing to do with the main plot, and contains a lot of private settings.
Purpose: Everyone should live a good life