Timeline/Build

A timeline of events in the World of Build.

20th century

 * c. 1943: Kimiyo Ubukata is born.
 * c. 1989: Kazumi Sawatari is born.
 * 1995: Along with her husband, Yuri Banjo serves as a security guard for the Synthetic Sciences division of Namba Heavy Industries, tasked with safeguarding the first unmanned space probe of Japan which had landed back on Earth. However, an alien substance enters her body in an attempt to possess her, rendering Yuri unconscious and leading her to be taken to a hospital, where it is discovered that she is a month pregnant.
 * Only one month later, Yuri gives birth to a healthy baby boy who is named Ryuga Banjo, a feat deemed impossible.

Undated

 * Juzaburo Namba adopts numerous orphans such as Fu Washio, Rai Washio, Nariaki Utsumi and Sawa Takigawa. Raised as "Namba Children", they swear alliegance to Namba Heavy Industries Ltd..
 * While still a child, Ryuga Banjo's parents are killed, believed to be the result of an accident.

21st century

 * 2008: The Sky Wall Disaster.
 * Icon-build.png 2015: Touto scientist Takumi Katsuragi proposes the use of Nebula Gas to evolve the human body but is declined by the government, with Gentoku Himuro noting that such operations could lead to monstrous mutations. Taking matters into his own hands, Katsuragi's attempt to experiment on a live subject is thwarted and his work for Touto is suspended, leading him to found Faust and create the Smash. The lengths he would go to prove his theory earn him the title Devil's Scientist.
 * Icon-build.png Soichi Isurugi, on behalf of Faust, steals the surface panels of the Pandora Box from the Touto Institute of Advanced Matter Physics. However, he soon after defects from the organization while taking his daughter Misora, who finally awakes after seven years, and a single panel with him.

2016

 * Utilizing the Enigma device to travel to a parallel world, Takumi Katsuragi makes two attempts to seize the essence of Kamen Rider Ex-Aid.
 * Arriving in the "World of Ex-Aid" during the Gamedeus Cronus crisis of 2016, Katsuragi, as Build intercepts Genm during his fight against the Bugster Virus. Mistaking him for Ex-Aid, Build engages Genm only to realize, after taking one of his lives, that he is not Ex-Aid, promptly taking his leave after introducing himself. Inspired by this encounter, Kuroto Dan later creates the Kamen Rider Build Rider Gashat.
 * Next appear in 2017 of the "World of Ex-Aid", Build fights through a pack of Bugsters engaged against Gamer Riders Ex-Aid and Para-DX. Requesting Ex-Aid's essence, Build is attacked by Para-DX but quickly defeats him before absorbing Ex-Aid's essence into a Fullbottle, stripping Emu Hojo of his transformation. Seeing Build returning to his world, the Bugster Parado attempts to follow him only to end up stranded in the World of Build for the following two years.

2017

 * Icon-build.png c. September 2nd: Anticipating his demise, Takumi Katsuragi leaves a USB containing his research data with his mother. Leaving a hoax at Touto Bank safety deposit box number 3405 should it be pursued, Katsuragi arranges for his data to be buried underground outside Nanba Heavy Industries Composite Materials Laboratory.
 * Icon-build.png September 5th: Taro Satou is hired by Takumi Katsuragi to deliver a drug for him.
 * Icon-build.png September 9th: In the morning, Katsuragi confronts "Soichi Isurugi" with the knowledge that he is actually Evolto, and Ryuga Banjo is his seperate half, announcing his intention to stop him. However, Katsuragi is easily incapacitated and rendered unconscious by Evolto as Blood Stalk.
 * apx. 9:00AM: Having been driven there by his friend Tatsuya Kishida, Taro arrives at Katsuragi's place only to find him unconscious. He is quickly killed by Evolto, who uses his power to swap the likenesses of the unconscious Katsuragi and Taro's cadaver.
 * apx. 10:00AM: "Takumi Katsuragi" is found dead by Ryuga Banjo.
 * Icon-build.png "Soichi Isurugi" finds and adopts the amnesiac Takumi Katsuragi. Naming him Sento Kiryu, "Soichi" offers him a home at nascita.
 * Guided by "Soichi Isurugi", Sento becomes Kamen Rider Build to defeat the Fang Smash.

2018

 * As Kamen Rider Build, Sento Kiryu saves journalist Sawa Takigawa from the Needle Smash.
 * Prison guard Masahiro Nabeshima delivers Ryuga Banjo to Faust, whom subject him to Nebula Gas before he escapes their clutches. Banjo is intercepted by Sento who, realizing their common connection to Faust, decides to protect the fugitive after saving him from the Strong Smash.
 * Sento Kiryu demonstrates his transformation into Kamen Rider Build's RabbitTank Form as well as the new GorillaMond Form.
 * In a video filmed for FausTube, Gentoku Himuro demonstrates his transformation into the Transteam System, Night Rogue.
 * Ryuga Banjo demonstrates his transformation into Kamen Rider Cross-Z and the Dragonic Finish.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * In a video filmed for FausTube, Gentoku Himuro demonstrates his transformation into the Transteam System, Night Rogue.
 * Ryuga Banjo demonstrates his transformation into Kamen Rider Cross-Z and the Dragonic Finish.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * In a video filmed for FausTube, Gentoku Himuro demonstrates his transformation into the Transteam System, Night Rogue.
 * Ryuga Banjo demonstrates his transformation into Kamen Rider Cross-Z and the Dragonic Finish.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Ryuga Banjo demonstrates his transformation into Kamen Rider Cross-Z and the Dragonic Finish.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Ryuga Banjo demonstrates his transformation into Kamen Rider Cross-Z and the Dragonic Finish.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.
 * Discretely entering Touto, Kamen Rider Grease recovers Hokuto's Phoenix and Robot Fullbottles from Build while he is occupied fighting Guardians with Cross-Z at night.

2019

 * January 14th:
 * Seeing Grease relinquish his Kuma and Televi Fullbottles, Massugu Ubukata becomes an Ice Smash in an attempt to reclaim them only to be defeated when they are wielded by Build. Learning the story of his family, Sento hands over the Fullottles for Massugu to return to Grease while encouraging him to go back to Hokuto to take care of his grandmother.
 * Acting on Blood Stalk's behalf, Nariaki Utsumi arrives at nascita to help Sento prepare for his Proxy Battle, providing additional Fullbottles to use against simulated Smash. Acting personally as Night Rogue, Utsumi helps Sento to collect data for a killswitch to handle the Hazard Trigger. Soon after, Sento is called to a facility containing Fullbottles for Touto, which he finds being attacked by what he recognizes as the "Bikaiser" accompanied by Faust Guardians.
 * Transforming into Build, Sento defeats the Guardians and Bikaiser, revealing the latter to be a test subject. Recovering the Nebulasteam Gun, Utsumi, having arranged the encounter to collect data himself, achieves a successful transformation into Hell Bro's.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Acting on Blood Stalk's behalf, Nariaki Utsumi arrives at nascita to help Sento prepare for his Proxy Battle, providing additional Fullbottles to use against simulated Smash. Acting personally as Night Rogue, Utsumi helps Sento to collect data for a killswitch to handle the Hazard Trigger. Soon after, Sento is called to a facility containing Fullbottles for Touto, which he finds being attacked by what he recognizes as the "Bikaiser" accompanied by Faust Guardians.
 * Transforming into Build, Sento defeats the Guardians and Bikaiser, revealing the latter to be a test subject. Recovering the Nebulasteam Gun, Utsumi, having arranged the encounter to collect data himself, achieves a successful transformation into Hell Bro's.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.
 * Constructing a Clone Hell Bro's, Utsumi tests it against a succession of simulated Kamen Riders before pitting it against Sento Kiryu. Instructing Build to use the Same and Bike Fullbottles to defeat the Clone Hell Bro's, Utsumi uses the data collected from the battle to create a new breed of Clone Smash.

Behind the scenes
Taking place in its own distinct world, Kamen Rider Build premiered on September 3rd, 2017. As a general rule, the dating of the Kamen Rider Series is assumed to correspond at least roughly to its real world broadcast. Indeed, Kazumi Sawatari's phonescreen as seen in the eighteenth episode, shows a date of January 14th, a match to the episode's broadcast in 2018. However, the day shown on the phone is Monday (月), which would instead correspond to 2019. There are two possible explanations for this - either this is a reference to how Sento Kiryu has been Build for a year before the series start, or it is a production mistake that happened when they deliberately set the phone's date to match the airing date, but neglected to notice the incorrect year.

Nevertheless, this sole example of dating serves as a hitching post for Build's chronology. Meanwhile, the series itself typically recalls past events by how many years ago they occured (e.g. the pivotal Sky Wall Disaster occurs ten years prior to the series).