The continent of Volcanica is very different from both Aradite and Mogull. Aradite used to be the demon continent until the humans came around to invade them. Mogul was the continent of the devil's and all the devil's living in Rivalle stayed over at Mogul. Meanwhile, Volcanica was the continent where the dragons and dragon slayers used to live, and it was also the continent with the most humans.
The humans that lived in Volcanica were separated into the dragon slayers and the non dragon slayers that were regular humans! Ever since the demon lord came to Volcanica and defeated all the dragons and their dragon slayers, the humans staying on Volcanica were all just regular humans.