This film is the third installment of the Ju-on series. The film was preceded by two low budget films from 2000 (Ju-on (2000) and Ju-on: The Curse 2 (2000)), whose storylines are continued in this sequel. 

It took 2 hours to apply the white makeup to Takako Fuji and Yuya Ozeki in order for them to play their ghostly incarnations of their characters. 

Kayako and Toshio are based on the Japanese legend of the Onryo, a vengeful spirit that unlike western ghosts, can physically manifest to attack and kill victims whereas our ghosts are just energy and can't physically appear. They manifest when they are killed in a state of deep rage as explained by the opening title card. 