Toshiko Sato, also known as Tosh, was a member of Torchwood Three in the 2000s. After being imprisoned by UNIT for assisting criminals under duress, Tosh was released by Jack Harkness under the condition that she work for Torchwood for five years. She was quiet and unassuming, generally using her computer genius to avoid exposure and to assist her colleagues. Nonetheless, she proved herself to be a field agent capable of taking on her own missions and projects. She had feelings for Owen Harper that she did not make known to him for quite some time.