Toshiko Sato

Beautiful, brilliant, yet insecure, much of Tosh's private life remains a mystery, although it's known she has living family with whom she maintains a close relationship.

She was born in London in 1975, though her parents moved to Osaka, Japan, in 1977, then back to the UK in 1986. Her Japanese-born grandfather (born January 20, 1920) was a decoder at Bletchley Park and her parents were in the RAF. Graduating from University in 1995, Toshiko got work with a Government think tank, and then in 2005 was hired by Torchwood. (TW: Greeks Bearing Gifts)

Toshiko met the Doctor when she was examining an alien pilot in the mortuary at Albion Hospital. She was slightly hurt when the alien pilot turned out to not be dead. (DW: Aliens of London)

Despite her crush on Owen Harper, Tosh had a lesbian affair with a female alien who tried to use their relationship to gain access to her technology, previously confiscated by Torchwood. In order to gain Toshs' confidence the alien allowed her the use of a pendant which allowed the wearer to read the mind of anyone around her.

Heroically Tosh used the device to save the lives of a woman and her child, about to be murdered in a tragic domestic incident, but she became suspicious of the device when its use gave her insight as to how her team mates regarded her. She destroyed the pendant following the defeat of the murderous alien.