Because We're Gemini is an alternate world in which Earth is in ruins, so people have harnessed the ability of a Zodiac sign in order to escape. These people created a new world known as Nībá. Unfortunately, there are some people who are unable to use a Zodiac ability, so they're usually left on Earth. Moreover, demons begin to be sent from Hell in order to punish the humans for failing to take care of the planet. Demons can be found on both Earth and Nībá, but Earth is more vulnerable due to not having Zodiac-using people.
Earth is unable to sustain most life, but there are designated locations that are approved to be safe living conditions. Most of Earth's areas are either deserts or suffer from immense flooding. However, a majority of the Earth is covered in toxic gas. Besides buildings that are for basic and social needs, such as hospitals and schools, not a lot of structures can be found around Earth either. The inhabitants of Earth tend be very spiteful, with expections of a few people. Because people cannot use a Zodiac ability, they cannot fight back against demons. As a result, everyone stays inside at night.
Due to being a much younger society, Nībá appears as a variation of Europe during the Renisiance Age. The houses and roads share a similar structure to that of the Renisiance. Clothing tends to be very different from Earthling apparel. Perhaps it is a way to distinguish itself from Earth. The inhabitants of Nībá are much more welcoming and open to new ideas, with exceptions of course.
In this society, there is a ruler. The very first ruler was an Aries, which is the first Zodiac sign. Since then, rule was merely passed down from parent to child. It also did not matter if the child of the ruler was biologically a male or a female. They just had to be a good ruler.
The ruler watches over Nībá and supervises any demon activity. People who go off to fight the demons are known as "Knights" and the ruler must choose a "Head Knight." The Head Knight trains the other Knights and is second in command to the ruler.
Catarina Frost 
Kitrina Frost