Riza Hawkeye is Roy Mustang's most trusted subordinate. She carries out many of the tasks he is too lazy to do, acts as his personal assistant, and protects him from danger. She also doubles as his voice of reason, keeping cool in heated situations and scolding him when he allows his emotions to get in the way. Riza and Roy seem to share a close relationship in both adaptations of Fullmetal Alchemist; in the anime she identifies him as her most precious person, whereas in the manga she loses her resolve to live when believing he has been killed. Riza specializes in firearms, particularly sniper rifles, and can hit nearly any target with lethal accuracy. She adopts a dog, called Black Hayate in both the anime and the manga, which she raises with stern discipline; when Hayate goes to the bathroom inside, she shoots at the wall behind him to reinforce that doing so is bad.

She meets the main character in the beginning of the manga. She ends up losing her emotion because of the infamous Stony Cat. She helps out Youto find the person who obtained his lost trait, in order to regain her own.