Mine is a member of the Night Raid assassination group within the Revolutionary Army. She grew up in the western borders of the Empire, where she endured harsh ridicule and misery because of her half-foreign blood. This experience of discrimination drove her to join the Revolutionary Army after learning it was forming alliances with western countries, with the hope that a new nation would emerge where people of her race could be accepted and future children would not suffer as she did.

Mine has a sharp tongue and quick wit, and she calls herself a genius sniper. She is initially quick to anger and easily irritated by people she does not know well, presenting a cold exterior. However, beneath this surface lies a warm and kind personality that she reveals to those she opens up to. Her defensive behavior is a coping mechanism developed from the harsh treatment she endured in childhood. As the series progresses, she becomes more open and expressive, forming deep emotional connections with her comrades. She also develops romantic feelings for Tatsumi, which he reciprocates, and the two enter an intimate relationship. Mine shows a jealous side in this relationship, particularly toward Leone's flirty advances toward Tatsumi, and she becomes deeply worried about his well-being when he is in danger.

Mine wields a powerful Teigu known as Roman Artillery: Pumpkin, a rifle that can fire in three modes: sniper, machine gun, and long barrel. It shoots highly concentrated piercing shots of spirit energy, and her precision allows her to strike targets with extreme accuracy. The weapon's energy output is proportional to her sense of danger, and it can overheat with continuous use. She can also switch parts on the weapon, such as one that lets her slash with spirit energy and another that allows quicker shots at the cost of attack power. She carries an eyepiece stored within the Teigu for scouting and sniping from a distance, and she is also adept in hand-to-hand combat. Her main weakness is a tendency to leave her back vulnerable to attacks.

Mine is the last member of Night Raid to appear on wanted posters, as her face is not widely known, which allows her to move casually through the capital when not on missions. In the anime adaptation, she is mortally wounded during the mission to rescue Tatsumi from execution and dies in his arms after they escape.