"Shin Shokugyo Koroshiya: Zan" is a manga series that blends action, dark fantasy, and psychological elements. The narrative centers on a world where humanity is plagued by monstrous creatures known as "Jobbers," which are manifestations of people's negative emotions and societal pressures. These creatures are tied to specific professions, and their existence disrupts the balance of society. To combat this threat, a specialized group of assassins, known as "Job Killers," is tasked with eliminating these entities.

The protagonist, Zan, is a skilled Job Killer who wields a unique weapon capable of destroying Jobbers. Zan's past is shrouded in mystery, with hints of a traumatic event that led him to this path. His stoic demeanor and relentless drive to eradicate Jobbers make him a formidable figure, though his methods often blur the line between justice and vengeance. Throughout the series, Zan encounters various Jobbers, each representing different professions and the psychological burdens associated with them. These encounters serve as both action-driven confrontations and explorations of societal issues, such as workplace exploitation, identity crises, and the dehumanizing effects of modern labor.

Supporting characters include other Job Killers and individuals affected by the Jobbers' presence. These characters provide additional perspectives on the world and its struggles, often highlighting the moral ambiguity of the Job Killers' mission. The series delves into themes of existentialism, the cost of survival, and the consequences of unchecked ambition. The plot progresses through episodic arcs, with each arc focusing on a specific Jobber and its connection to the broader narrative. As the story unfolds, Zan's past is gradually revealed, shedding light on his motivations and the origins of the Jobbers.

The manga maintains a tense and gritty atmosphere, with a focus on action sequences and psychological depth. The interplay between Zan's personal journey and the larger societal issues creates a layered narrative that balances character development with thematic exploration. The series does not shy away from depicting the darker aspects of its world, including violence, despair, and the moral dilemmas faced by its characters. Through its unique premise and intricate storytelling, "Shin Shokugyo Koroshiya: Zan" offers a compelling examination of human struggles within a fantastical yet eerily relatable setting.