"Leica no Kikan" is a manga series set in a post-apocalyptic world where humanity faces extinction due to a mysterious phenomenon known as the "Collapse." The story centers on Leica, a young girl who possesses the unique ability to manipulate time. This power makes her a key figure in the struggle to prevent the Collapse and restore the world. Leica is accompanied by a group of survivors, each with their own motivations and backstories, as they navigate the dangers of the ruined world.

The narrative unfolds as Leica and her companions embark on a journey to uncover the truth behind the Collapse. Along the way, they encounter hostile factions, mutated creatures, and remnants of advanced technology from the pre-Collapse era. The group's interactions and conflicts reveal the complexities of human nature in the face of survival, as well as the moral dilemmas posed by their mission. Leica's time-manipulation ability becomes both a tool for survival and a source of tension, as its use carries significant risks and consequences.

Key characters include Leica, whose innocence and determination drive the group forward; Kaito, a pragmatic and resourceful leader who often clashes with Leica's idealism; and Aya, a scientist whose knowledge of the Collapse provides critical insights but also raises ethical questions. The relationships between these characters evolve as they confront external threats and internal struggles, adding depth to the narrative.

The plot is structured around a series of episodic encounters that gradually build toward a larger revelation about the Collapse and Leica's role in it. The story balances action, mystery, and character development, with a focus on themes of hope, sacrifice, and the resilience of humanity. The world-building is detailed, with a mix of desolate landscapes, advanced technology, and remnants of a lost civilization, creating a vivid backdrop for the characters' journey.