Tōru Shirō (司狼 斗織 Shirō Tooru) (née Magami) is Kamui's mother and shadow sacrifice, as one of the Magami clan. Tōru burns along with the house that she and Kamui lived in while on Okinawa.
It is explained in the anime that she died to postpone or alleviate the disasters that would befall Kamui in the time leading up to the promised day (thus acting as his shadow sacrifice), and in the manga, that she acted as a sacrifice to prevent the premature destruction of the planet itself. Hinoto attributes Tōru's fiery death to the concentrated effect that global warming was having on the Earth. Originally, she was supposed to give birth to the first Sacred Sword, but Saya took her place. Tōru was personally in contact with the former Chairman of Clamp Academy — indeed, Tōru was just ending a phone call with her when the effects of acting as shadow sacrifice of Kamui/the Earth were set into motion, igniting her flesh.
Tōru's death occurs just prior to the beginning of the first volume of the manga (chronologically) and is what causes Kamui to return to Tokyo after a six year absence.
She dies in a similar fashion by being burned to death, however she was able to give Kamui his Sacred Sword while she was dying and her last words were for Kamui were for him to go to Tokyo for the final battle and informs him about the Dragons of Heaven and the Dragons of Earth at the beginning of the film.