so in the other world there are three groups
Gods, Humans, and Dragons, and the dragons are broken up into chaos and harmony dragons who fight eachother.
Tohru is a Chaos Dragon and presumably so are Fafnir and Kanna. Chaos Dragons fight against humans but seemingly its a war of survival between both of them
Harmony Dragons fight on the side of humans except Harmony Dragons require regular human sacrifices and are generally kind of assholes. Elma is a harmony dragon but she's fine with just getting food.
Lucoa is technically a banished god so she doesnt follow anyone besides what she wants to do.
In the first episode, Tohru got smited by a god which is why she escaped to the human world.