Natsuko Aki is a student at Shirobara Academy and the best friend and roommate of Honey Kisaragi. She has short dark hair, often wears red glasses, and has a few moles on her face. During the series, she becomes aware that Honey is an android after witnessing Honey transform to save a classmate. Her role in the story is that of a close confidante who learns the truth about Honey's nature, though her own motivations beyond loyalty to her friend are not deeply explored. She does not possess any combat abilities or special powers, serving instead as a link to Honey's civilian life and a witness to the extraordinary events unfolding around them. Her development is limited to the revelation of Honey's identity and her reaction to that discovery.