Nobara Yukinokouji is an atavistic descendant of the Yuki-onna, or snow woman, and serves as the Secret Service bodyguard of Renshou Sorinozuka in the Maison de Ayakashi. In her human appearance, she has long blonde hair, blue eyes, and wears glasses, with a height of 170 centimeters and a birthday on January 6. She is frank, straightforward, and sincere, but also possesses a strong interest in fashion and beautiful women, frequently perusing adult magazines and discussing them with Sorinozuka. Her personality is often described as maniac, and she has a tendency to become obsessive, as seen after surviving an attack by enemy youkai, when she became consumed with tracking them down, leading to her death during an investigation.

In the original timeline, Nobara was killed during the Hyakki Yakou incident. Twenty-three years later, she reincarnates at the age of fourteen while retaining her past memories and personality. Initially living with Sorinozuka, she later moves into the Ayakashi mansion to become Ririchiyo Shirakiin's Secret Service agent after Ririchiyo ends her contract with Soushi Miketsukami. Nobara works alongside Natsume, Sorinozuka, Karuta Roromiya, and Kagerou Shoukiin to prevent the next demon parade. She acts as a kind, affectionate older sister figure toward the younger female residents, particularly Karuta and Ririchiyo, though she can be harsh with certain male characters. Her youkai form is that of a Yuki-onna, wearing a long white dress, and she possesses abilities over ice and cold, capable of freezing opponents at close range.