"No Guns Life" is set in a dystopian future where cybernetic enhancements, known as Extended, have become commonplace. The story centers on Juzo Inui, a former soldier turned Resolver—a private investigator specializing in cases involving Extended. Juzo himself is an Extended, with his head replaced by a large, gun-like apparatus, giving him the appearance of a humanoid firearm. His past is shrouded in mystery, and he struggles with fragmented memories of his time as a soldier.

The narrative begins when Juzo is hired by a mysterious woman to protect a young boy named Tetsuro Arahabaki. Tetsuro is an Extended who has been experimented on by the powerful Berühren Corporation, which seeks to exploit his unique abilities. As Juzo delves deeper into the case, he uncovers a conspiracy involving Berühren and its rival corporations, all vying for control over advanced Extended technology. The series explores themes of identity, autonomy, and the ethical implications of human augmentation.

Key characters include Mary Steinberg, a skilled engineer who assists Juzo with technical support and repairs, and Pepper, a former Berühren operative with her own agenda. The antagonist, Harmony, is a high-ranking executive at Berühren who orchestrates many of the experiments on Extended, including those involving Tetsuro. Throughout the series, Juzo confronts various adversaries, including other Extended and corporate enforcers, while grappling with his own fragmented past and the moral complexities of his work.

The plot is driven by Juzo's efforts to protect Tetsuro and uncover the truth behind the experiments, all while navigating a world where corporate greed and technological advancements blur the lines between humanity and machinery. The series balances action-packed sequences with moments of introspection, as Juzo and the other characters confront the consequences of their choices in a society where the boundaries of human and machine are increasingly indistinct.