From the introduction:
Here's the back facts: Ever since a huge upheaval twenty-two years ago that tore Kanegawa prefecture off of the mainland of Japan, around two percent of all children born in the resulting island (known as “the Muraji Special Economic District” or more colloquially known as “the Lost Ground”) have the power to access energy from an alternate energy dimension called the “Other Side” to deconstruct nearby matter and recompose it into manifestations known as Alter. Each Alter's form and abilities vary - depending on the person using it, but most are dangerous in nature and thus the government of the civilized areas of the lost ground (such as it is) relies on its specialized Alter and non-Alter using police forces, HOLY and HOLD, to keep the peace from uncivilised “native Alter users.” While nominally under the power of the mainland government, until the last story arc of the series the real power in these areas rests in the hands of HOLY, the Alter-using branch of the police force. The “civilized areas” of the lost ground only comprise a minor percentage of the land areas, however, with the rest at more of a post-apocalyptic society level. Things are slowly getting better though, with the civilized area slowly spreading outwards and the people of the uncivilized areas banding together in large farming communities... but for now, the place is mostly a post-apocalyptic wasteland filled with chaos. What's more, the basis for the “civilized government” of the lost ground is heavily unstable, and relies on massive propping up from the behind-the-scenes movers and shakers from the mainland to continue functioning.
It is in this chaos that Kazuma and Ryuuho, a native Alter user and an elite HOLY agent, are about to meet and set into motion a chain of events that will upset the whole house of cards.