Sanae Izumi, also known as Yūhi, serves as a maid in the Hyuuga household and is the older sister of Minori Izumi. She frequently appears publicly alongside Mayuki Hyuuga and his companions during their activities. A core aspect of her identity remains hidden: she functions as one of Seiran Shinano's two controlled "dolls." When activated into her combat-ready aya form, she wields a specialized pair of claws as her primary weapons.

Her existence in this role results from Seiran Shinano's abilities as a doll user, binding her to his directives. This stands in contrast to her everyday persona, where she engages socially with Mayuki and his friends. Her sisterly connection to Minori positions her within the group dynamics surrounding Mayuki. Her established narrative centers solely on these dual roles and combat function.