Saeko Tanaka is a former student of Karasuno High and the older sister of Ryuunosuke Tanaka. She was also a classmate of the Small Giant during her high school years. The second years of the volleyball team views her as a cool older sister, especially Nishinoya, but Tanaka thinks of her as a nuisance whenever she bothers his study sessions. Like her brother, she's loud and outspoken. Her driving has been described by her brother as dangerous as he had once stated to Hinata and Kageyama that he can't guarantee their safety in her car.