Karen commands Resistance Group 11, a human faction battling machine overlords in a post-apocalyptic world where machines subjugated humanity after war. The loss of her younger sister, Touka, during the initial machine uprising shapes her resolve and fuels her fight, surfacing in recurring flashbacks like memories of picking flowers with Touka before the attack.

She coordinates human survivors in guerrilla combat against robotic forces, wielding dual pistols and utilizing flight-capable devices for mobility during engagements. Operating within urban environments, she frequently encounters hostile machines during everyday activities, demanding constant combat readiness. The narrative examines her tactical choices and the ethical burden of commanding high-risk missions.

Her experiences drive an exploration of themes like the nature of humanity, machine sentience, and the concept of the soul. These themes emerge through her interactions with both humans and machines, including encounters that challenge distinctions between organic and artificial life, such as depictions of human-machine relationships involving transactional exchanges of mechanical components.

Visually, she features distinctive elaborate attire contrasting with her combat role. Her character design and movements are rendered entirely in 3D CG animation, influencing her physical expressiveness and action sequences.