With their resident genius stranded, Ianto (Gareth David-Lloyd) and Owen are unable to open the Cardiff spacetime Rift and save her until Toshiko leaves them the necessary equations, which she is forced to write in her own blood.

[9] In the second series (2008) episode "To the Last Man", Tosh has a relationship with a soldier from 1918 (Anthony Lewis), who had to be frozen and re-awoken every year until the time was right for him to return to 1918 and heal the Rift.

[12] In the episode "Fragments", the audience comes to understand how Toshiko came to work for Torchwood; Captain Jack rescued her from a UNIT detention centre where she was held after she was forced to build a sonic modulator for an unnamed terrorist organisation.

By initiating the final log-off procedure for her account on the Torchwood computer system, Ianto activates a pre recorded message from Toshiko, in which she thanks Jack for saving her.

The first wave, Another Life by Peter Anghelides, Border Princes by Dan Abnett, and Slow Decay by Andy Lane, were published in January 2007 and form a loose story arc.

[16][17][18] Published in March 2008, and tying in with the concurrently airing second series of Torchwood, Toshiko appears in the novels Trace Memory by David Llewellyn, The Twilight Streets by Gary Russell, and Something in the Water by Trevor Baxendale.

[23][24] Skypoint, set after "A Day in the Death" and before "Exit Wounds", depicts Tosh and Owen masquerading as a couple in order to investigate an alien sighting in a luxury apartment complex.

Speaking of the decision to cast her in Torchwood executive producer Russell T Davies stated: "she was absolutely brilliant [in Doctor Who], and I knew then that I wanted to bring her back".

[29] Toshiko has a "very strong bond" with her boss Jack Harkness though is "not scared of expressing her opinions with him" and is shown to have a crush on colleague Owen Harper who Mori feels to be "one of those guys you can't help but really like ... and fancy a little bit".

[29] Torchwood producer Richard Stokes felt that in her characterisation of Toshiko "Naoko ... has a real vulnerability that you completely believe" and stated the character to be "emotionally the opposite to Owen".

[30] Mori felt the Toshiko centric episode "Greeks Bearing Gifts" to be "a real learning curve" that makes the character "stronger" and well as "more truthful and honest".

[35] Digital Spy reviewer praised the character's storyline in "To the Last Man" feeling that Toshiko "bears all the emotions of the episode" and that the audience have a sense "of her blossoming as a woman".

[36] Alan Stanley Blair reacted negatively to Toshiko's subsequent storyline, feeling that "Mori has so much more to give this series and it is painful to watch her relegated to unrequited love status".