"Zephyr in December" is a manga series set in a dystopian future where humanity is on the brink of collapse due to environmental devastation and societal decay. The story centers on Zephyr, a young woman with a mysterious past, who possesses the rare ability to manipulate wind currents. This power, known as "Aerokinesis," makes her a target for both oppressive government forces and rebel factions vying for control over the remnants of civilization.

The narrative begins with Zephyr living in isolation in the ruins of a once-thriving city, scavenging for survival while avoiding detection. Her life takes a dramatic turn when she encounters Kael, a rogue scientist who reveals that her abilities are linked to a long-lost genetic experiment designed to create individuals capable of restoring balance to the planet. Kael convinces Zephyr to join him on a perilous journey to locate other "Aerokinetics" like herself, who are scattered across the wasteland.

As Zephyr and Kael traverse the desolate landscape, they face numerous challenges, including hostile factions, mutated creatures, and the harsh environment itself. Along the way, they uncover fragments of the truth about the experiments that created Zephyr and the catastrophic event known as "The Collapse," which led to the world's current state. The story delves into themes of survival, identity, and the ethical implications of scientific advancement, as Zephyr grapples with her role in either saving or further destabilizing the world.

Key characters include Zephyr, whose internal conflict between her desire for freedom and her sense of duty drives much of the narrative; Kael, whose motives remain ambiguous as he oscillates between ally and manipulator; and a group of Aerokinetics with diverse abilities and personalities, each representing different facets of humanity's struggle. The series balances action-packed sequences with introspective moments, exploring the psychological toll of living in a fractured world.

The plot builds toward a climactic confrontation between Zephyr's group and the authoritarian regime seeking to exploit their powers for control. The resolution hinges on Zephyr's decision to either embrace her role as a savior or reject the burden of responsibility, leaving the fate of humanity hanging in the balance. The manga's intricate world-building, layered characters, and morally complex narrative make it a compelling exploration of resilience and hope in the face of despair.