"She's a Steely Woman!" centers on the life of Aoi Kirishima, a young woman with a reputation for her unyielding and stoic demeanor. Aoi works as a security guard at a high-end department store, where her no-nonsense attitude and exceptional physical prowess earn her both admiration and fear from colleagues and customers alike. Her ability to remain calm under pressure and her unwavering sense of justice make her a formidable presence in her workplace.

The narrative explores Aoi's interactions with a diverse cast of characters, including her coworkers, customers, and individuals who challenge her principles. Among these is Haruto Tachibana, a cheerful and somewhat naive new employee who becomes Aoi's unlikely partner. Haruto's optimism and clumsiness often clash with Aoi's rigid personality, creating a dynamic that balances humor and tension. Despite their differences, the two develop a mutual respect as they navigate various workplace challenges together.

The plot delves into Aoi's backstory, revealing the events that shaped her into the person she is today. A tragic incident from her past, involving the loss of someone close to her, serves as the foundation for her commitment to protecting others and upholding justice. This backstory is gradually unveiled through flashbacks and interactions with secondary characters, adding depth to her character and explaining her steely resolve.

Throughout the series, Aoi faces a variety of situations that test her principles and abilities. These range from handling shoplifters and diffusing tense confrontations to dealing with personal dilemmas that force her to confront her emotions. The manga balances action-packed sequences with moments of introspection, highlighting Aoi's growth as she learns to reconcile her tough exterior with her underlying vulnerability.

The supporting cast includes a mix of recurring characters, such as Aoi's strict but fair supervisor, a rival security guard with a competitive streak, and a mysterious figure from her past who resurfaces to challenge her worldview. Each character contributes to the overarching narrative, either by providing comic relief, advancing the plot, or offering insight into Aoi's character.

"She's a Steely Woman!" combines elements of action, drama, and slice-of-life storytelling to create a compelling narrative. The series emphasizes themes of resilience, justice, and the importance of human connection, all while maintaining a focus on Aoi's journey as she navigates the complexities of her personal and professional life.