Rukia is a demon serving within the Moderate Faction of the demon world, directly under Ramus as a maid in his household. She executes her duties with serious dedication, maintaining a calm and composed demeanor that contrasts with her younger sister Maria Naruse's impulsiveness. This professional dedication defines her role without eclipsing her personal bonds.

Rukia is Maria Naruse's older sister, demonstrating protective care and consistent concern for her well-being. When Maria faints after losing a duel during the tournament arc, Rukia personally ensures her safety by carrying her to a waiting room. She also places trust in Maria's friend, Kurumi Nonaka, entrusting her with a special jewel capable of sealing dark spirits, showing reliance on allies beyond family.

Like Maria, Rukia possesses succubus heritage, granting specific battle capabilities. In combat, she undergoes a transformation, adopting a distinct battle form that enhances her physical abilities, representing a significant aspect of her demonic nature used for protection or conflict. This positions her as a capable fighter when necessary.

Shella is confirmed as Rukia's mother, establishing their direct lineage. Rukia operates within the demon world's power structures, aligned with Ramus's Moderate Faction. Her presence is noted during key events, such as the tournament between Basara Toujou and Demon Lord Leohart's faction, where she appears alongside faction members Shella, Noel, and Ramus. Her involvement reinforces her role within the faction's activities and hierarchies, reflecting her status as a trusted subordinate.