Durga I is the sister unit of FRAME ARMS GIRL Magatsuki.

The original FRAME ARMS model Magatsuki has the role of guarding the lunar surface in its setting, and it shares a majority of its parts with its sister unit, Durga I.

FRAME ARMS GIRL's Durga I also inherits some of this setting, and is built to share parts with FRAME ARMS GIRL's Magatsuki.
While FRAME ARMS GIRL incorporates designs reminiscent of samurais and ninjas into its armor, Durga I features a design that evokes the image of blonde hair, a lance, and knights.
Although they are sister units, they are not too similar; the design also focuses on how well they display when placed next to each other.