"Talentless Nana" is a supernatural thriller anime set in a world where humanity faces an existential threat from mysterious creatures known as the "Enemies of Humanity." To combat this threat, children born with extraordinary abilities, called "Talents," are trained at a secluded island academy. The story centers on Nana Hiiragi, a seemingly ordinary girl who enrolls in the academy. Initially, Nana appears kind and supportive, quickly earning the trust of her classmates. However, her true identity is revealed early on: she is not a Talent but an operative sent by the government to eliminate the Talents, who are believed to be the real Enemies of Humanity.

The narrative unfolds as Nana systematically targets her classmates, using her intelligence, manipulation, and strategic planning to eliminate them one by one. Each Talent possesses unique abilities, ranging from super strength to time manipulation, making Nana's missions increasingly complex. Her actions are driven by a belief that the Talents pose a greater danger to humanity than the external Enemies, a perspective shaped by her government's propaganda. However, as the story progresses, Nana's convictions are challenged by her interactions with the Talents, particularly Michiru Inukai, a kind-hearted girl with the ability to transform into a wolf. Michiru's unwavering trust and friendship force Nana to confront the morality of her mission and the true nature of the Enemies of Humanity.

The series is structured around a cat-and-mouse dynamic, with Nana's schemes often pitting her against Kyouya Onodera, a highly intelligent and perceptive classmate who begins to suspect her true intentions. Kyouya's deductive skills and resourcefulness make him a formidable adversary, creating tension as he inches closer to uncovering Nana's secrets. The plot is driven by a combination of psychological manipulation, moral dilemmas, and unexpected twists, with each episode revealing new layers to the characters and the overarching mystery of the academy's purpose.

As the story progresses, the line between friend and foe becomes increasingly blurred. Nana's internal conflict grows as she grapples with the consequences of her actions and the possibility that she has been misled about the true nature of the Talents. The series explores themes of trust, betrayal, and the ethical implications of sacrificing individuals for the perceived greater good. By the end of the first season, the narrative leaves several questions unanswered, setting the stage for potential future developments in the story.