"Made in Abyss" is set in a world centered around the Abyss, a massive, enigmatic chasm filled with ancient relics and dangerous creatures. The Abyss is divided into layers, each with its own unique ecosystem and increasing levels of peril as one descends. The story begins in Orth, a town built around the edge of the Abyss, where Cave Raiders, known as Delvers, risk their lives to explore its depths and retrieve artifacts.

The protagonist, Riko, is a young orphan who dreams of becoming a legendary Cave Raider like her mother, Lyza, who disappeared during an expedition. Riko’s life changes when she discovers a mysterious robot boy, Reg, who emerges from the Abyss with no memory of his origins. Reg possesses advanced technology, including extendable arms and a powerful incinerator beam, which make him a valuable companion for exploration. Together, Riko and Reg decide to venture into the Abyss to uncover its secrets and find Lyza, who is believed to be waiting at the bottom.

As they descend, Riko and Reg encounter various challenges, including hostile creatures, environmental hazards, and the Curse of the Abyss, a mysterious phenomenon that afflicts those who ascend from its depths. The Curse manifests in increasingly severe symptoms, ranging from nausea and hallucinations to death, depending on the layer. The duo is joined by Nanachi, a former human transformed into a hollow by the Abyss’s experiments, and their companion, Mitty, a tragic figure who embodies the darker consequences of the Abyss’s mysteries.

The narrative delves into themes of survival, sacrifice, and the human desire for discovery, often juxtaposing the wonder of exploration with the brutal realities of the Abyss. The layers of the Abyss are meticulously crafted, each presenting unique challenges and revelations about the world’s history and the nature of its inhabitants. The story also explores the moral ambiguities of the Delvers’ quest, as well as the ethical dilemmas surrounding the Abyss’s experiments and the exploitation of its resources.

Riko’s determination, Reg’s loyalty, and Nanachi’s wisdom form the emotional core of the series, as they navigate the treacherous depths and confront the mysteries of the Abyss. The plot is driven by their quest to uncover the truth about Lyza, the Abyss, and Reg’s origins, while also addressing the broader implications of humanity’s relationship with the unknown. The series balances moments of wonder and discovery with intense, often harrowing challenges, creating a compelling narrative that explores both the beauty and brutality of the Abyss.