Takahashi stated that the film's objective as the first film in the Reiwa-era is to answer the question as to "what is a Kamen Rider" to new fans. Although the film was a crossover between Zi-O and Zero-One, scriptwriter Takahashi was told by producer Shirakura that the film's story did not necessarily have to intertwine both, but he found it particularly difficult not to.
Takahashi decided to use the film's opportunity to explore the secret origins of Aruto's powers and introduced Kamen Rider Type-1 to achieve this. He differentiated the film from the series in that the film explores how the Humagear sees humans, as opposed to vice versa.
The film's story focuses entirely on Aruto and his relationship with his father. As Zi-O had elements of time travel, Takahashi sent Aruto back in time to interact with his father, who was already deceased by the events of the first episode. He stated that if viewers rewatched the first episode after seeing the movie, they'd gain a deeper understanding on what happened to Soreo during the Daybreak Town Accident.