Species: Human
Occupation: Military Officer, Briggs General
Weapon: A family heirloom sword
Known relatives: Philip Gargantos Armstrong (father), Mrs. Armstrong (mother) Alex Louis Armstrong (younger brother), Catherine Elle Armstrong (youngest sister), Amue Armstrong (younger sister), Strongine Armstrong (younger sister)

Major General Olivier Mira Armstrong is Alex Louis Armstrong's older sister. She is in charge of Briggs, the northern military border. She scoffs at the concept of "equivalent exchange" and believes "survival of the fittest" is the only law in life. Her subordinates are loyal, but if it ensured the survival of Briggs (or for the sake of the greater good), they are instructed to leave her to die if ever the need arose, and she wouldn't hold it against them.

Being the General of Briggs, Olivier has full command of the Fortress. She is also very skilled with her family heirloom sword which she uses unhesitatingly. She also seems to have some proficiency with tanks and artillery.