Naoko Mori is a Japanese actress . who a lot of people know from her roles as Mie Nishikawa in Casualty ( 1993-1994 ) , and as Toshiko Sato in Doctor Who and Torchwood . Naoko Mori ( born November 19 , 1971 ) is a British actress of Japan descent known for roles as Sarah , Saffron 's ` odd ' friend in Absolutely Fabulous , Mie Nishikawa in Casualty , and Toshiko Sato in Doctor Who and Torchwood .