The Orbment Revolution heralded a time of great prosperity for people. By using the mysterious energies harnessed by the mechanical engines called Orbments, there has been great leaps in technology, such as the development of airships, and the products of this are indelibly linked to everyday life. At the same time, the strongest countries have developed numerous Orbment-based weapons in bids to outdo each other, each with an eye on world domination.

In this world, there is an organization which transcends national boundaries, the Bracer's Guild. The guild devotes itself to protecting the peace of the land, and the safety of civilians. Upon request, its members undertake various quests such as the extermination of monsters and crime prevention, and they may even mediate disputes between governments.

Estelle and Joshua are two young members of the guild who find themselves in opposition to the organization Ouroboros, whose actions have shaken the country of Liberl to its very foundation. And when Joshua leaves to pursue Ouroboros on his own, Estelle goes after him with the aid of fellow guild members Klose, Olivier and Scherazard.