Director Ryuta Tasaki had been a fan of the original Kamen Rider, where the concepts of "hero subjected to human experiments where he comes out stronger and fights monsters on a motorcycle" was fascinating to him, with Build being heavily inspired by such. The original concept for Build was that after Ryuga Banjo had escaped from jail, he'd meet and see Build as sort of a master, later becoming Cross-Z himself in his capacity as a pupil. After writer Shogo Muto was hired, he revised the story so that both characters would be buddies instead, allowing both characters to guide each other as opposed to it only going one way. Because the story revolves around the Fullbottles, Producer Omori felt that introducing the Pandora Box as a MacGuffin would make writing easier and more focused for Muto.
"It has been 10 years since the Pandora Box was discovered on Mars and caused the Sky Wall tragedy. Our country was divided into Touto, Seito, and Hokuto, resulting in untold chaos."
"It has been 10 years since the Sky Wall tragedy. In the attempt to open the Pandora Box and release its massive amount of energy capable of destroying the world...a new battle has begun."
"The Pandora Box, which contains enough energy capable to destroy the Earth, has finally been opened. The alien lifeform Evolto controls that power...but the Kamen Riders stand against him!"
10 years ago, the Pandora Box was discovered on the planet Mars and brought forth a catastrophe that would forever change the country of Japan. In the years following the Sky Wall Disaster, the rising of the Sky Wall divided the country into three warring territories: Touto (Eastern Capital), Hokuto (Northern Capital) and Seito (Western Capital), and created a series of unidentified monsters known as Smash that relentlessly attack the public. To combat this chaos, the Touto government requested the help of Sento Kiryu, a genius and prodigious physicist to help decipher the mysteries left behind by both the Pandora Box and the Smash. Alongside prison escapee Ryuga Banjo, who was wrongfully framed for a murder he did not commit, the duo embark on a journey as Kamen Riders to uncover the mysteries surrounding the Pandora Box, the Smash, and their own pasts. Their journey would not come easy as they face adversaries from Hokuto and Seito, whom they must ultimately confide in if they are to have any hope in stopping their mutual enemy, Evolto from destroying the planet that they hold dear.
Episode 01-14 - Story Arc: Faust (「ファウスト」編,Fausuto Hen)
Episode 15-22 - Story Arc: Invasion of Hokuto (「北都侵攻」編,Hokuto Shinkō Hen)
Episode 23-33 - Story Arc: Invasion of Seito (「西都侵攻」編,Seito Shinkō Hen)
Episode 34-41 - Story Arc: Evolto (「エボルト」編,Eboruto Hen)
Episode 42-49 - Story Arc: New World Creation (「新世界創造」編,Shin Sekai Sōzō Hen)
Similar to the previous series, half of each episode's title is an English word, though spelled in katakana instead of English letters, and the other is written in kanji, similar to the transformation announcements of most Best Match Forms. Most of the episodes contain formulas from mathematics or physics to form each episode number in the title cards.
This series is the final Rider series to have a full televised run in the Heisei Era.
With this series, Kamen Rider's timeslot changes from 8am to 9am starting in October.
This series opening credits reuse the same font style that was used in Kamen Rider Ex-Aid.
In keeping with the science motif, a few of the equations, graphs, formula and matrix seen in the background or Rider's finisher in the show are based on math, scientific theories or scientific principles. These objects are provided by professors from Keio University, Kyushu University, Kyoto University and JSPS after a discussion of how to show characters' emotion symbolically.
According to series writer Shogo Muto, he had planned on "reseting" the world in the show's finale from the very start. He states that Sento's monologues in the beginning of all the episodes were indicative of this and did not tell anyone this for the entire duration of production.