Origa Calmeria is a catgirl with distinctive aubergine hair and orange eyes, exhibiting feline traits including ears and a tail. Her attire commonly features a scarf and a bandaged leg.

Enslaved by the Kaiser Empire from a young age, she endured forced training as an assassin, earning the epithet "Twilight Assassin." Her missions involved imperial-coerced assassinations, including one targeting King Ranze of Wimburg.

During this assassination attempt, Seiichi Hiiragi intervened, subdued her, and removed her slave collar, freeing her from imperial control. He then provided refuge and adopted her into a sisterly familial role.

Origa fights with dual knives, utilizing agility and precision rooted in her close-quarters assassination training and covert operations background.