Aki Jōgamine is a high school student who is being trained as a Brave, individuals tasked with eliminating demon kings in an alternative 21st century. She becomes the reluctant apprentice of a down-and-out Brave named Yashiro, who is known as the Reaper, after he is hired to serve as her private teacher. Jōgamine is characterized as a self-proclaimed student, showing a determined and persistent nature as she seeks to learn from a seasoned but unwilling mentor.

Her primary motivation is directly tied to the death of her father. The truth behind his murder is a significant plot point that casts a shadow over her journey and drives her actions as she pursues the path of a Brave. In the story, she is a central figure who, alongside fellow students Sara and Yukine, receives training from Yashiro. Her key relationships include her bond with her instructor, Yashiro, and her comrades, Sara and Yukine, as they are often put in dangerous situations together.

Throughout the series, Jōgamine shows notable development in her abilities, growing beyond her initial limits in combat as she gains experience from the perilous missions she undertakes with her group. As a Brave in training, she is involved in hunting ether-enhanced demon kings, though the full scope of her specific combat skills is not detailed in available information.