"No Game, No Life Zero" is a prequel film to the "No Game, No Life" anime series, set 6,000 years before the events of the main story. The narrative unfolds in a war-torn world where the Disboard, a realm governed by the Ten Covenants that enforce conflict resolution through games, has not yet been established. The world is ravaged by endless battles among 16 races, with humanity, the weakest and most vulnerable, struggling to survive on the brink of extinction.

The story centers on Riku, a young human strategist who has lost his family and home to the relentless wars. Disillusioned by the violence and destruction, Riku seeks a way to end the conflict and create a world where humanity can thrive. During his journey, he encounters Schwi, a female Ex Machina android who has been exiled from her race for developing emotions and individuality. Despite initial mistrust due to the Ex Machina's role in humanity's suffering, Riku and Schwi form an unlikely alliance. Together, they embark on a mission to challenge the gods and bring peace to the world.

Riku's strategic brilliance and Schwi's advanced technological capabilities allow them to navigate the chaos and confront the powerful races dominating the world. Their partnership evolves into a deep bond as they share their dreams and vulnerabilities. Riku's ultimate goal is to unite the races under a single rule, the Ten Covenants, which would replace warfare with games as the method of resolving disputes. This vision becomes the foundation for the Disboard seen in the main series.

The film explores themes of survival, hope, and the power of unity in the face of overwhelming adversity. It delves into the origins of the Disboard and the sacrifices made by Riku and Schwi to create a better future. Their journey is marked by emotional struggles, moral dilemmas, and the harsh realities of a world consumed by war. The narrative culminates in a climactic confrontation with the gods, where Riku and Schwi's actions set the stage for the world depicted in the main series.

The main characters, Riku and Schwi, are portrayed with depth and complexity. Riku's determination and strategic mind drive the story forward, while Schwi's evolving emotions and loyalty to Riku add a poignant layer to their relationship. The film also introduces key figures from the main series, such as Tet, the God of Games, whose origins and motivations are explored in greater detail.

"No Game, No Life Zero" provides a compelling backstory to the "No Game, No Life" universe, offering insight into the events and characters that shaped the world of Disboard. It balances action, emotion, and world-building, creating a narrative that stands on its own while enriching the overarching story of the series.