Zero Two is an artificially-created life form and elite pilot with an infamous reputation as the "Partner Killer" who aspires to become fully human. She is well known for addressing Hiro , the protagonist, by the eponymous term " darling ". Zero Two is considered one of the most popular characters of Darling in the Franxx and her personality has been well received by both fans and critics, with the latter typically citing her as one of the best aspects of the series. Zero Two had the most labor-intensive design process and was designed to be an iconic character to act as a flagship for Darling in the Franxx.

Darling in the Franxx is set in a dystopian future where youth are artificially created and indoctrinated solely to defend the remnants of civilization. The story follows a squad of ten pilots, particularly focusing on the partnership between Hiro, an esteemed former prodigy, and Zero Two, a hybrid human and elite pilot who aspires to become entirely human. The series features symbolism relating to the mythological Jian , an imperfect bird with only one eye and wing and thus may only fly when paired with another.

She is a human-klaxo sapien hybrid and a member of the APE Special Forces, primarily fighting on the front lines. As an elite Parasite with the codename "", also known as the "Partner Killer", Zero Two had always accepted solitude due to her horns and Klaxosaur blood. Despite having no regard for human life or her own and being accustomed to fighting solo, she took interest in Hiro and offered an opportunity to pilot with her, making him her new partner and "darling". Over time, Zero Two developed romantic feelings towards Hiro.