Production
In 1999, Koji Suzuki concluded the Ring series by including a fourth entry titled Birthday, which collected three short stories that filled in details of the story. Asmik Ace decided to hire Ring and Ring 2 screenwriter Hiroshi Takahashi to adapt the short stories of Birthday, Takahashi decided to only adapt the story Lemonheart from Birthday due to the complex nature of the short story collection. Lemonheart captured the life of the character of Sadako just before she was consigned to the fate seen in the later Ring series. Hideo Nakata was offered to direct Ring 0, while Kenji Kawai was offered the chance to compose the music of the film by Takasige Ichise, the producer of Ring and Ring 2; however, both Nakata and Kawai turned down the offer.
Once Ring 0 went into production, numerous changes were made to the film production staff. The director for the film was the first change, as Nakata was replaced by Norio Tsuruta. Tsuruta had previously worked on direct-to-video horror scripts such as Honto ni atta kowai hanashi (Scary True Stories) in 1991, and wrote and directed the sequel. After working on two pachinko-themed feature films in between 1993 and 1994 and eight direct-to-video horror works between 1991 and 1996, Tsuruta subsequently took a hiatus for nearly three years. Tsuruta's first work after his hiatus was "Tatari", the second episode of the Kansai TV Tanpatsu drama Haunted School: Spring Haunting Special in March 1999, which Tsuruta directed while Takahashi took responsibility for the screenplay. Tsuruta was offered the chance to direct by Takahashi, due to their having previously collaborated on "Tatari". Tsuruta referred to the film as "a tragedy" with a theme about "a young woman who is oppressed because she is different from everyone else. In Japan, there is great pressure not to stray too far from the norm". The assistant director for Tsuruta would be Shozo Katashima. The second change was the cinematographer, which would now be handled by Takahide Shibanushi. The third change was the sound recording and reproduction director, which was previously handled by Kiyoshi Kakizawa in Ring 2; he was replaced by Tetsuo Segawa, a veteran sound recording director who started his sound recording career during the late Japanese New Wave era. The fourth change was the sound effects director, which was handled by Kenji Shibazaki in Ring and Ring 2; however, Shibazaki was replaced by Shizuo Kurahashi, a veteran sound effects editor/designer when the film went into production. The fifth change was the script supervisor, which was handled by Kumiko Yoshida in Ring 2; however, Yoshida was replaced by Yoshimi Amaike when the film went into production. The last change for the film production staff was the art director, which was handled by Iwao Saito on Ring, Spiral and Ring 2; however, Sato was replaced by Osamu Yamaguchi when the film went into production. Genre-wise, Ring 0 retained the J-Horror trappings found in Ring and Ring 2. However, the techno-horror genre that made Ring famous was now abandoned in favor of psychological thriller, a genre that many Hollywood directors as well as some East Asian filmmakers had already explored, such as David Fincher, David Lynch, Martin Scorsese, M. Night Shyamalan, Satoshi Kon and Kiyoshi Kurosawa, but many other East Asian filmmakers and screenwriters, including Tsuruta and Takahashi themselves, were not familiar with.
Yukie Nakama was cast in the role of Sadako. After Nakama's friends had seen Ring, they teased her about her resemblance to Sadako. Nakama was later contacted by her agent, who mentioned they were looking for actresses for the role of Sadako and tried out for the role. She received confirmation of her having been cast in the role two weeks later.
