"Space Sagittarius" is a science fiction anime series set in a distant future where humanity has expanded across the galaxy, forming interstellar colonies and encountering various alien species. The narrative centers on a group of young cadets from the Sagittarius Military Academy, an elite institution training the next generation of space explorers and defenders. The cadets are thrust into a high-stakes mission when a mysterious alien artifact is discovered on a remote planet, triggering a chain of events that threatens the fragile peace between human colonies and alien civilizations.

The protagonist, Kael Ardent, is a determined and resourceful cadet with a troubled past, driven by a desire to uncover the truth about his family's disappearance during a previous interstellar conflict. Alongside Kael are his fellow cadets: Lyra Voss, a brilliant but socially awkward engineer; Zane Torrin, a hot-headed pilot with a knack for improvisation; and Mira Solis, a strategic thinker with a deep sense of duty. Together, they form an unlikely team tasked with investigating the artifact, which is revealed to be a piece of ancient technology capable of manipulating space-time.

As the cadets delve deeper into the mystery, they uncover a conspiracy involving rogue factions within the human military and a powerful alien race known as the Veylari, who seek to reclaim the artifact for their own purposes. The story explores themes of trust, sacrifice, and the consequences of wielding advanced technology, as the cadets navigate political intrigue, interstellar warfare, and their own personal struggles. The artifact's true nature becomes a focal point, with its potential to either unite or destroy civilizations.

The series balances episodic missions with an overarching plot, gradually revealing the history of the galaxy and the motivations of key characters. The cadets' relationships evolve as they face moral dilemmas and confront their own limitations, highlighting the complexities of leadership and teamwork in a volatile universe. The narrative builds toward a climactic confrontation where the cadets must decide whether to destroy the artifact or risk its power falling into the wrong hands, setting the stage for future developments in the series.