Yoko lived at the Kawai complex before Sayaka, Ritsu, and Usa moved in. She had terrible luck with jobs. So bad she was compared to Mayumi in terms of if you take Mayumi has bad luck with men and switch it with Yoko has bad luck with jobs you'd be 100% accurate. She wanted to move back but was turned down due to complications. She appears in the manga Vol. 4 Chapter 37.