Kaisers

Kaisers (カイザー) is the name of several Kamen Rider-like villains in Kamen Rider Build, including the following characters:

Origin
The Kaiser System was originally developed by Kaisei Mogami of the World of Build in conjunction with his counterpart from the World of Ex-Aid. Joining forces, they became the Bi-Kaiser, only to be defeated by Kamen Rider Build.

Hell Bros
Acting on behalf of Blood Stalk and Nanba Heavy Industries, Nariaki Utsumi updated the Kaiser System. Its test subject was a man who was abducted and exposed to Nebula Gas. However, instead of becoming a Smash, he was provided with a Nebula Steam Gun to become the prototype Nebula Hell Bros. Accompanied by a squad of Faust Guardians, Nebula Hell Bros was sent to attack a Touto facility holding Fullbottles. He was confronted by Sento Kiryu who, recognizing the model as a Bi-Kaiser, initially believed him to be Kaisei Mogami, the man who originally developed and used the Kaiser System to transform.

After scrapping the Guardians in ToraUFO Form, Kamen Rider Build assumed KirinCyclone to engage the Bi-Kaiser before switching to KujiraJet to defeat him. With the Kaiser transformation canceled, Sento found the subject to be a mere amnesiac whom he took to safety. Meanwhile, Nariaki Utsumi, having used the battle to finalize the new Bi-Kaiser he created, recovered the Nebula Steam Gun left behind by the Nebula Hell Bros which, upon inserting the Remocon and Engine Gears, transformed him into the complete Bi-Kaiser Hell Bros.

Ultimately, the Nebula Steam Gun and Gears were granted to brothers Fu and Rai Washio, whom served as soldiers of Seito, which CEO Juzaburo Namba backed to dominate Japan. These new Hell Bro's Kaisers proved superior in power to the Hard Smash Hazards as well as the Kamen Riders prior to Rogue.

Arsenal

 * Nebula Steam Gun - Transformation device
 * Gears - Transformation trinkets

Appearances

 * Icon-build.png Kamen Rider Build
 * Icon-exaid.png Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders
 * Kamen Rider Build: Raising the Hazard Level ~7 Best Matches~
 * First Chapter
 * Next Chapter
 * Episode 23: The Phantom of the West
 * Episode 24: A Man Called Rogue
 * Episode 25: The Idol Awakens
 * ROGUE