The Lost Ground is an island that was divided from Japan during a major earthquake called "The Great Uprising". The land that was separated was once part of the Kanagawa Prefecture near Tokyo. There are two sides to the island. The first is the "Inner" where the cities and mainstream life continue, with support from the mainland. The other side, which is divided by a great wall, is unsupported and relies heavily on the resources that are either grown on the island or provided to them from the "Inners". There is also a forest populated by animals endowed with Alter power.
The Lost Ground is also the primary birthplace of Alter Users, humans endowed with the power to deconstruct and reshape matter at a molecular level.