"Darling" is a science fiction anime series set in a dystopian future where humanity faces extinction due to mysterious creatures known as Klaxosaurs. To combat this threat, humanity develops giant humanoid robots called Franxx, which are piloted by pairs of young individuals, one male and one female. The pilots are referred to as "Parasites" and are raised in isolated facilities, trained from a young age to operate the Franxx. The story primarily revolves around Hiro, a former prodigy who struggles to find a partner after failing to synchronize with previous co-pilots. His life takes a turn when he encounters Zero Two, a mysterious and highly skilled pilot with a reputation for being dangerous to her partners. Zero Two, who is part-human and part-Klaxosaur, forms a unique bond with Hiro, and the two become an exceptional team.

The narrative explores the dynamics of the Parasites as they navigate their roles in the ongoing war against the Klaxosaurs while grappling with their own identities, emotions, and relationships. The series delves into themes of love, sacrifice, and the meaning of humanity, as the characters uncover the truth about their world and the origins of the Klaxosaurs. Key characters include Ichigo, the squad leader who harbors feelings for Hiro; Goro, Hiro's loyal friend; and the other members of Squad 13, each of whom has distinct personalities and struggles. As the story progresses, the Parasites begin to question the authority of the adults who control their lives, particularly the enigmatic organization known as APE, which governs the Franxx program.

The plot intensifies as Zero Two's true nature and her connection to the Klaxosaurs are revealed, leading to conflicts within the squad and raising questions about the morality of their mission. The series builds toward a climactic confrontation that challenges the characters' understanding of their purpose and the future of humanity. Through its exploration of complex relationships and existential themes, "Darling" presents a layered narrative that combines action, romance, and philosophical inquiry.