"Gangsta" is a seinen manga series set in the fictional city of Ergastulum, a lawless urban sprawl dominated by crime syndicates, corrupt officials, and mercenaries. The narrative revolves around the Handymen, a duo of freelance problem-solvers who take on jobs ranging from odd tasks to dangerous missions. The Handymen consist of Nicolas Brown, a deaf superhuman known as a Twilight, and Worick Arcangelo, a gigolo with a sharp mind and a mysterious past. Twilights are individuals enhanced by a drug called Celebrer, granting them extraordinary physical abilities but often at the cost of shortened lifespans and societal ostracization.

The story delves into the complex dynamics of Ergastulum, where power struggles between criminal factions, such as the Monroe Family and the Cristiano Family, shape the city's underworld. Nicolas and Worick navigate this treacherous environment while confronting their own traumatic histories. Nicolas, a former slave and enforcer, struggles with his identity and the stigma attached to Twilights, while Worick, the illegitimate son of a powerful family, harbors resentment and guilt over his past actions. Their partnership is both professional and deeply personal, rooted in mutual reliance and shared experiences of violence and betrayal.

As the narrative progresses, the Handymen become entangled in larger conflicts, including the rise of a militant group targeting Twilights and the machinations of powerful figures seeking to control Ergastulum. The series explores themes of discrimination, morality, and survival, with a focus on the marginalized Twilight population and the ethical ambiguities of the characters' actions. Supporting characters, such as Alex Benedetto, a former prostitute seeking redemption, and various members of the criminal underworld, add depth to the story, highlighting the interconnected lives of Ergastulum's inhabitants.

The plot is driven by a mix of action, intrigue, and character development, with a strong emphasis on the moral gray areas of its protagonists and antagonists. The series balances intense, gritty combat sequences with quieter moments of introspection, creating a narrative that is both visceral and emotionally resonant. "Gangsta" presents a dark, immersive world where survival often comes at a cost, and the line between hero and villain is frequently blurred.