Adaptation Toei announced the film in June 2024, with the voice cast from
Fuuto PI's anime adaptation reprising their roles. Due to the popularity of the anime adaptation, initial plans for the theatrical version involved continuing its story, but scheduling constraints at
Studio Kai prevented an immediate continuation. After a discussion between director
Yōsuke Kabashima and Studio Kai's production manager, Daisuke Furuya, they agreed that adapting the entire manga series was difficult and opted to adapt each manga volume into their own films or
original video animations instead. The production team had initially considered adapting either the fourth manga volume—which featured the Puzzle Dopant, a character absent from the web anime—or the seventh volume, which introduced Kamen Rider Accel. However, the production team decided that featuring Kamen Rider Skull was the most critical element for attracting audience interest, leading to the selection of the sixth volume for adaptation. Kabashima studied
Kamen Rider W: Begins Night to prepare for the production. However, he cut certain aspects he disliked of
Kamen Rider W's treatment of Skull's story. Nagi Ōshima was created as an original character for the movie.
Development Kabashima praised the performance of the two main actors, stating that they needed minimal guidance. He commended Tsuda's performance as Narumi for his easy-going portrayal and faithfulness to the original live-action television series. Kabashima named
Masami Obari as a major directorial influence for his animation choices. He combined 3D animation with 2D animation in several scenes, such as the first time Shotaro enters Narumi's office. Similarly, Kabashima named Tsuda's portrayal of Narumi as one of the best parts of the work. Kabashima had been impressed by Kikkawa's portrayal of Narumi in
Kamen Rider W: Begins Night, and hoped that Tsuda would also play the character well, particularly what he described as Narumi's cool aspects. The antagonist Ōshima was voiced by
Jun Fukuyama. Kabashima emphasized Ōshima's ear piercings, gifts from Saeko, as a reflection of his humanity. Kikkawa sought to convey Narumi's perspective when singing the song. As part of this process, he read the script, formed a mental image, and then created lyrics that fit the story. The song's lyrics were intended as a message of encouragement to the young people featured in the film. The song "Nobody's Perfect" was serendipitously included; Kabashima added the song as a test while editing and felt that it perfectly matched a scene in the film. ==Release==