Formerly known as Aoi Zenjou (禅城 葵, Zenjō Aoi?), she is the childhood friend of Kariya Matou. She is a descendant of the Zenjou family, every mothers of which gave birth to talented childs because of some magical factor, though the Zenjou have since become a family of ordinary people and Aoi herself has no Magic Circuits. She became the wife of Tokiomi, adopting his surname, and gave birth to two daughters, Rin and Sakura, who both possessed great inherent potential as mages.
She accepted Tokiomi's proposal with full knowledge of what it meant to marry a mage. While Kariya loved her as well, he peacefully gave up pursuing her affections because she seemed happy accepting Tokiomi's proposal. It is implied that Aoi and Kariya remained in touch, given that her daughters, especially Sakura, were fond of Kariya's company. Tokiomi's sudden decision to give Sakura away to Zouken Matou comes as a shock to Aoi, though she does not openly oppose his decision. She leaves at the beginning of the Holy Grail War with Rin to live at her parents' home for the duration of the conflict.
Aoi has long, dark green hair and eyes of the same color.
Aoi is a passive and loyal woman who does not interfere with her husband's affairs, described by Kirei Kotomine as the ideal version of a traditional wife.
She gives off the feeling of a well-raised young lady who became a mother, and she was designed to be a different type of "ideal mother" than Irisviel. Irisviel embodies a "fun mother", while Aoi is a "peaceful mother" who is better at using the "hidden power" that is inherent to mothers. She gives off the strong feeling of "That husband of mine, never taking care of himself", and while she looks like Rin at a glance, her behavior is more like that of Sakura.
During the Holy Grail War, when Rin ran away to find her friend Kotone, who had been kidnapped by Caster, Aoi is so anxious for her that she returns to Fuyuki City looking for her. Later on, Kariya gives Rin back to Aoi after he finds her, which is also how Aoi finds out about his condition and his resolve to kill Tokiomi.
On the final day of the war, Aoi finds her husband dead, with Kariya present in the room, however, being unaware that Kirei was responsible for Tokiomi's death and that Kariya had arrived to confront Tokiomi only after the man was dead. In her grief, she blames Kariya and the Matou family for taking away both Sakura and her husband and claims that Kariya never loved anyone. With both his resolve and heart crushed, he violently strangles Aoi.
She survives the war, but is confined to a wheelchair and suffers from brain damage, not understanding that Tokiomi is dead and Sakura is gone. Rin takes care of her mother, but feels lonely as her mother's condition leaves her isolated. Aoi does not make an appearance in Fate/stay night, and Kotomine is shown as Rin's sole guardian.
In accordance to Tokiomi's will, Aoi inherits the properties and the estates of the Tohsaka family in trust for Rin, however both management of the estate and guardianship of Rin is managed by Kotomine due to Aoi's mental deterioration.
 Fate/Zero material - Characters: Aoi Tohsaka, p.040-041, 087
Height: 160 cm
Weight: 50 kg
Blood type: O
Birthday: September 5
Three sizes: B78/W57/H82
Image color: Light yellow-green
Talents: Smoothing a situation over
Things she likes: Mysterious things, nighttime strolls
Things she hates: Swimming
Worst enemy: None
Comment for Aoi
Takeuchi: She has the feeling of a well-raised young lady who became a mother. She was supposed to be a different type of "ideal mother" than Iri.
Urobuchi: Iri is the fun mama while Aoi is the peaceful mama, huh? But I imagine Aoi is better at using that hidden power that mothers have.
Takeuchi: You also get a strong feeling of "That husband of mine, never taking care of himself" from her. Personally, I have the image that while she looks like Rin at a glance, her behavior is like that of Sakura.
Urobuchi:WoooW, that's a really high level fusion!
Comment for Aoi
- Fate/Zero Anime Visual Guide I - Characters: Aoi Tohsaka entry, p.036
 Fate/Zero material - Encyclopedia: Tohsaka Aoi [Person's name], p.100-101
Aoi Tohsaka [Person's name]
Tohsaka Tokiomi's wife, and Rin and Sakura's mother. Her maiden name is Zenjou.
Though the Zenjou family had a magus ancestor many generations ago, now they are simple commoners with no connection to the magical world at all. Nevertheless, the blood flowing through their veins contains a very unique trait, which was noticed and pursued by Tohsaka Tokiomi. As a result of accepting this courtship, Aoi gave birth to two sisters with absolutely preposterous magical potential.
Unlike her daughter Rin, Aoi fully understood that Tokiomi possessed an inhuman sense of values, but she still blindly loved her husband anyway. Maybe she, too, bore some distortion within herself, just like Tokiomi did. If that's the case, she probably wouldn't have been able to build a happy home even if she had married Kariya…
By the way, the activation of Tokiomi's "Tohsaka family goof-up trait" only occurs in serious, life-threatening situations. In his normal family life at home, he was an utterly perfect superman, in the same way Rin would eventually be a perfect honors student at Homurahara Academy in Fate/stay night. I hear that both Aoi and Rin were huge fans of his "cool dad" style.
- Fate/Zero:Prologue 3 - Baka-Tsuki
 Fate/Zero material - Encyclopedia: Tohsaka Tokiomi [Person's name], p.101
Tokiomi Tohsaka [Person's name]
The fifth Tohsaka family head. Had everything gone according to plan, he would have been the man to finish the Holy Grail War once and for all.
He started making preparations for the Fourth Holy Grail War long before it ever began. But although he had set up everything perfectly in his favor, he was tragically killed by his trusted ally, Kotomine Kirei. Well, seeing as how the one who tempted Kirei into defecting in the first place was Gilgamesh, in a sense you could say Tokiomi died due to a lack of compatibility with his Servant.
Tokiomi and his predecessor made a conscious effort to commercialize their spiritual lands, and the unnatural economic success of every business situated there naturally led to exorbitant rental fees, which were collected by the Tohsaka. Of course, as far as Tokiomi was concerned, the fact that the "harvests of all the tenant farmers tilling the Tohsaka land" were protected from bad luck and natural disasters by the Tohsaka's careful management of the ley lines, meant that taxing them like this was his natural right. Truly, it was a 20th century feudal system made possible through sorcery.
Although, even among the Second Owners of other lands, very few have ever seen monetary returns like those made by the Tohsaka.
After Tokiomi's death, these assets were passed on to Aoi, and after Aoi's death they were passed on once more to Rin. Or at least, they should have been, but thanks to her legal guardian Kirei's naïve honesty and crude management, most of the valuable property was lost to other people. Then again, as a priest who values honest poverty, he probably thought it would be good for her from an educational standpoint. Just another thing for Rin to wallop him for, I guess.