The Gun Knights are the spirits of historic firearms, given human form. They are bound to their Masters and fight alongside them. Each Gun Knight carries the memories and legacy of the battles they were part of, and their personalities reflect the history and character of the firearms they embody.

The world was once ruled by the tyrannical World Emperor, who subjugated nations through sheer military might. After his fall, the nations of the world regained their independence, but the scars of war remained. The sudden appearance of Brown Bess at the British Queen's coronation signaled a new era—one in which nations would seek out and awaken their own Gun Knights to serve as both guardians and national symbols.

These Gun Knights are not merely weapons; they are companions, warriors, and living embodiments of history. Each has their own will, their own sense of pride, and their own reasons for fighting alongside their Master.