"Osiris no Tenbin" is a science fiction anime series set in a futuristic world where humanity has colonized the solar system. The story revolves around the Osiris Project, a secretive government initiative aimed at creating genetically engineered humans known as "Osiris Children." These individuals possess enhanced physical and mental abilities, designed to serve as elite soldiers and agents. The narrative centers on Neiro, a young Osiris Child who escapes from the facility where she was raised, seeking freedom and answers about her existence.

Neiro's journey leads her to encounter a diverse group of characters, including other Osiris Children who have also fled the project. Together, they uncover the dark truths behind their creation, including the unethical experiments and manipulation they were subjected to. The series explores themes of identity, autonomy, and the ethical implications of genetic engineering, as Neiro and her companions struggle to define their purpose beyond the roles imposed on them by their creators.

The plot is driven by the conflict between the Osiris Children and the shadowy organization that seeks to reclaim them. As Neiro and her allies evade capture, they uncover a larger conspiracy involving the exploitation of their abilities for political and military gain. The series balances action-packed sequences with introspective moments, delving into the emotional and psychological struggles of the characters as they grapple with their past and fight for a future of their own making.

Key characters include Neiro, the determined and resourceful protagonist; Kaito, a fellow escapee who becomes a close ally; and Dr. Aoi, a scientist with a mysterious connection to the Osiris Project. The antagonists are represented by the project's overseers, who view the Osiris Children as expendable tools rather than individuals. The narrative builds toward a climactic confrontation, where the characters must confront their creators and decide their own fates.

"Osiris no Tenbin" presents a thought-provoking exploration of humanity, free will, and the consequences of scientific ambition, set against a backdrop of futuristic technology and interstellar intrigue. The series combines elements of action, drama, and science fiction to create a compelling story that challenges viewers to consider the ethical boundaries of human innovation.