Chiyo Fujiwara is a central character in the series 'Ane Naru Mono' (The Elder Sister-Like One). She is a mysterious demon who appears to be in her late teens or early twenties. Chiyo forms a contract with the protagonist, Yuu, to become his 'big sister' and caretaker. While her true form is that of a powerful and ancient being, she takes on a gentle and caring demeanor, often displaying a playful and teasing personality. Her role is crucial as she guides and protects Yuu, helping him navigate the complexities of life with both wisdom and kindness.