He is one of the enactors of the curse, which states that when someone dies amidst rage and intense wrath, those feelings remain at the death site and kill whoever it touches.

Toshio was born to Takeo and Kayako Saeki, a Japanese couple residing in Nerima City, Tokyo on July 27, 1987.

Takeo took Mar from Toshio and killed it with the same box cutter used previously to torture Kayako, then buried the cat in the dirt path beside their house.

Takeo eventually found the truth years afterward and killed his wife, igniting the curse to include Kayako as well.

He is also able to possess a person and leaving them at will; doing this ensures the survival of his second mortal incarnation long enough to be adopted by Reo's family, thus dooming them.

Similar to the original, Toshio's mother has a crush on his teacher – in this case, Peter Kirk – and this obsession leads to a misunderstanding with his father.

His maternal grandmother is Nakagawa Kawamata, his aunt is Kayako's younger sister, Naoko, and his uncle by marriage is Daisuke.