"Luger Code 1951" is a science fiction anime series set in a dystopian future where humanity is on the brink of extinction due to a mysterious alien threat known as the "Ethereals." The story unfolds in the year 1951, a pivotal moment when the remnants of human civilization are locked in a desperate struggle for survival. The narrative centers around a covert military unit called the "Luger Unit," tasked with developing advanced weaponry and strategies to combat the Ethereals. The unit operates under the command of the enigmatic Dr. Luger, a brilliant but morally ambiguous scientist whose past is shrouded in secrecy.

The protagonist, Kaito Shirogane, is a young soldier recruited into the Luger Unit after displaying exceptional combat skills and an uncanny resistance to the Ethereals' psychic attacks. Kaito's journey is intertwined with the unit's mission to uncover the origins of the Ethereals and develop a weapon capable of defeating them. Alongside Kaito are key members of the unit, including Aya Fujisaki, a tactical genius with a tragic past, and Ryoma Takeda, a veteran soldier grappling with the psychological toll of endless warfare. The group's dynamic is further complicated by the presence of Rei, a mysterious girl with a direct connection to the Ethereals, whose true nature becomes a focal point of the story.

As the series progresses, the Luger Unit uncovers a series of shocking revelations about the Ethereals, including their connection to humanity's own technological advancements and the possibility that they may not be entirely alien. The plot delves into themes of survival, sacrifice, and the ethical dilemmas of warfare, as the characters are forced to confront the consequences of their actions. The narrative builds toward a climactic confrontation between the Luger Unit and the Ethereals, with the fate of humanity hanging in the balance. The series concludes with an open-ended resolution, leaving room for interpretation regarding the ultimate outcome of the conflict and the characters' futures.