"No Guns Life" is set in a cyberpunk world where advanced 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 a distinctive and imposing appearance. 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 to protect a young boy named Tetsuro Arahabaki, who has been implanted with a dangerous and highly sought-after control unit called the "Harmony." This device allows its user to manipulate other Extended, making Tetsuro a target for various factions, including the powerful Berühren Corporation, which seeks to exploit the Harmony for its own purposes. As Juzo takes on the case, he becomes entangled in a web of corporate intrigue, military conspiracies, and ethical dilemmas surrounding the use of Extended technology.

Throughout the series, Juzo encounters a diverse cast of characters, each with their own motivations and connections to the world of Extended. Mary Steinmetz, a skilled engineer and Juzo's ally, provides technical support and repairs for his cybernetic body. Pepper, a former Berühren employee, becomes a key figure in uncovering the corporation's secrets. Meanwhile, Juzo's investigations often bring him into conflict with other Resolvers, corporate enforcers, and rogue Extended, all vying for control or survival in a society where power is increasingly concentrated in the hands of those who control technology.

The plot delves into themes of identity, autonomy, and the consequences of technological advancement. Juzo's journey is not only one of solving cases but also of piecing together his own fragmented past and grappling with the moral implications of his actions. The series balances action-packed sequences with moments of introspection, exploring the human cost of a world where the line between man and machine is increasingly blurred.

As the story progresses, Juzo's connection to Tetsuro deepens, and the two form an unlikely bond. Their relationship becomes a focal point, highlighting the tension between Juzo's hardened exterior and his underlying sense of duty and compassion. The narrative builds toward a confrontation with the forces behind the Harmony and the broader implications of its existence, culminating in a climactic struggle that challenges Juzo's resolve and forces him to confront his own humanity.