This film is the third installment of the Ju-on series. The film was preceded by two low budget films from 2000 known as (Ju-on: The Curse (2000) and Ju-on: The Curse 2 (2000)), whose storylines are continued in this sequel.
Toshio's spirit is often heard meowing throughout the film. Not only does this imply that his spirit merged with his deceased cat Mar, but it also relates to an old Japanese legend where the damned spirits of lost children become strays and as a result, produce a cat's meow.
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 Western 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.
Yuya Ozeki is terrified of cats in real life, making filming any scenes with Toshio's pet cat Mar rather troublesome.
Sam Raimi helped Sony option the remake rights, as he was a big fan of this film, saying it terrified him.
The house used in the film was not a constructed set but a real location, which had to be rented for film production. It became a tourist attraction following the film franchise's popularity. The house was demolished in 2019.
In a form of irony, the reason the Saeki family have a black cat as a pet is because in Japanese folklore, it is said that owning a black cat will bring good luck and fortune, in stark contrast to their ultimate fates as vengeful ghosts.
Technically, this is the first film in the Ju-On series that received a theatrical release. The previous film, Ju-on: The Curse 2 (2000), had a very limited theatrical release before going straight to video.
The backstory that creates the curse in this series is strongly reminiscent of the myth of Oiwa, a traditional Japanese onryo (resentful ghost) legend. Oiwa was a housewife disfigured and brutally murdered by her unfaithful husband. She returns to haunt him and makes him murder his new lover. According to the legend, a curse accompanies her story, and that those who retell it will suffer injuries and even death. The disfigured aspect of the onryo is likely what inspired Sadako Yamamura's appearance in Ringu (1998).
Takako Fuji, Takashi Matsuyama and Yuya Ozeki would reprise their roles as the doomed Saeki family in the American remake The Grudge (2004). Ozeki had to be recast for The Grudge 2 (2006) as he had noticeably gotten older.
Included among the "1,001 Movies You Must See Before You Die" edited by Steven Schneider.
Author Kei Ohishi had written a novelization for the film to expand upon Kayako's backstory.
Ryota Koyama, who played Toshio in Ju-on (2000) and Ju-on: The Curse 2 (2000), had outgrown the role by the time production commenced and was recast with Yuya Ozeki.
Chikako Isomura's last film before her death of natural causes in 2006. Her likeness was used as a tribute to her in the film Ju-on: White Ghost (2009).
The only film in the Ju-on series that has Kayako wearing a different haircut compared to all the other films (including the American remakes). Although she is known for having long and straight jet-black hair, here she is wearing a short and wavy bob haircut at her shoulders with bangs.
Yôji Tanaka previously appeared in Ringu 0: Birthday (2000) featuring another iconic J-horror antagonist Sadako Yamamura. Both franchises would crossover in Sadako vs. Kayako (2016).
Shuri Matsuda would go on to appear in The Grudge 2 (2006), an American remake of the Japanese films.
Megumi Okina would collaborate with Masayuki Ochiai in the remake of Shutter (2008). He specifically cast her in the film as a fan of the Ju-on series. He would go on to direct the reboot of the Ju-On series, Ju-on: The Beginning of the End (2014).
Shuri Matsuda and Yukako Kukuri, who play Kazumi and Miyuki, are friends of Takashi Shimizu in real life, and cast them in the film as a result.
Kayako is not only based on the Japanese Onryo, she also has a spider motif to her ghostly appearance. She usually crawls out of the attic or small dark spaces, and spiders are known for hiding in dark and dusty corners of the house, she also sometimes crawls out of the trash bag Takeo stuffed her in, a reference to spiders bursting out of the cocoon of eggs. Kayako is basically impossible to avoid, as there's no way to rid yourself of the curse, a reference to the fact that it's nearly impossible for prey to escape a spider's web.