Leone is one of the older and more experienced members of Night Raid, the elite assassination unit operating under the Revolutionary Army to overthrow a corrupt empire. She originally hails from the slums of the imperial capital, where she grew up in harsh conditions and learned to survive by working as a masseuse and occasionally swindling people. Her path toward rebellion began when she killed a nobleman who had made a game of trampling poor children with his horse, an act that led to her recruitment by the Revolutionary Army and later by Night Raid. Within the group, she primarily handles intelligence gathering and confirms the validity of assigned targets, earning a reputation for exercising calm judgment even under pressure.

In terms of personality, Leone is relaxed, cheerful, and openly casual, often displaying a lack of ladylike manners such as putting her feet on the table, drinking large amounts of sake, or joking in a carefree manner. Despite this easygoing exterior, she is fiercely loyal to her comrades and deeply intolerant of injustice. She serves as a big‑sister figure to the younger members of Night Raid, especially the protagonist Tatsumi, whom she mentors and protects with maternal warmth. Her primary motivation is to dismantle the oppressive imperial regime and protect the innocent, a conviction rooted in her own background of suffering and survival.

Leone’s role in the story extends beyond combat. She is often the one who first interacts with new recruits and verifies mission requests, acting as a steady anchor for the team. Her key relationships include a close bond with Tatsumi, whom she initially swindles before bringing him into Night Raid and later treating as a little brother. She also shares strong camaraderie with fellow members such as Akame and Mine, and her support for them underscores her loyalty and protective nature. Over the course of the series, Leone undergoes notable personal growth, evolving from a somewhat self‑centered survivor into a dedicated revolutionary who commits her life fully to the cause and the well‑being of her allies.

Leone’s most distinctive ability comes from her Imperial Arm, the King of Beasts Transformation: Lionel, a belt she acquired on the black market. When activated, it transforms her into a kemonomimi with feline features, granting enhanced strength, speed, agility, and greatly sharpened senses. It also provides powerful regenerative capabilities, enabling her to heal from serious wounds quickly. Her ultimate technique, Lion Never Dies, allows her to regenerate even severed limbs. In the series’ climax, Leone is stripped of her Imperial Arm by Prime Minister Honest and suffers fatal gunshot wounds, yet she survives long enough by sheer willpower to corner and kill the prime minister, ensuring his defeat. Afterward, she spends her remaining hours visiting old acquaintances and eventually dies peacefully in the slum where she once lived, a satisfied smile on her face.