Ringu (1998) and Spiral (1998) were shot back-to-back from the novels by Koji Suzuki and released in theaters as a double bill. After audiences hated The Spiral, Asmik Ace Entertainment hired the cast and crew of the original to make this replacement sequel Ring 2.
The only film in the Japanese Ringu series that is not based on Koji Suzuki's novel series of the same name, or any of his written works. This is because the film was hastily produced less than a year after the first film to quickly replace Rasen (1998), which was panned by audiences for being too dissimilar to the first film.
The number 4 appears in this film (the mentioning of 4 victims from the first film who all died at the same time, Mai Takano and Yoichi ride in a car with number 4 on the front window on their way to Yamamura Inn, the spirit photography Polaroids are laid out on the table as a set of 4). In Japan and some Asian countries, the numerical digit 4 is considered an unlucky number and is associated with death (due to the words 4 and death sounding similar in their native languages). The fear of the number 4 is known as tetraphobia and is taken seriously in some Asian countries that sometimes the number 4 is avoided in homes, hospitals, businesses and other properties.
Isao Yatsu, who plays Takushi, also appears in Ju-on: The Grudge (2002) and the American remake The Grudge 2 (2006). Both franchises would cross over in Sadako vs Kayako (2016).