Sento Kiryu

1="Now, shall we begin the experiment?"

- Build's catchphrase

2="Build up!"

- Build's call whenever he changes forms

Sento Kiryu (桐生 戦兎) is a genius theoretical physicist who experiments with Full Bottles to further enhance his abilities as Kamen Rider Build (仮面ライダービルド) to fight against the evil Smash organisms.

History
Little is known about Sento as he has amnesia and has no memory of his past, with the exception of a single memory where he was being experimented on by a being known only as Nightrogue.

Seeking a sample of Ex-Aid's essence, Build mistakenly intercepted Kamen Rider Genm while he was fighting through the Bugster Virus hordes of Gamedeus Cronus. Switching to the GorillaMond Best Match to engage him, only after eliminating one of Genm's lives did Build realize that he was not Ex-Aid and promptly took his leave after identifying himself to Dan.

Personality
"You know, in spite of how it may seem, I'm actually a pacifist."

- Build to Genm

Sento has a couple of catchphrases. Before a fight, he says "Now, shall we begin the experiment?" (さあ、実験を始めようか？). After a finishing move, he says "The laws of victory have been decided." (勝利の法則は決まった).

Powers and Abilities

 * Genius-Level Intellect: TBA

Forms
Sento sets two different Full Bottles into the Build Driver and turns the crank to transform into Kamen Rider Build. Kamen Rider Build, like Kamen Riders Double and OOO before him, can assume a variety of different forms, called Trial Forms, using different combinations of Full Bottles. However, each one has a "Best Match" with another Full Bottle that creates an especially powerful form and sometimes provides a unique weapon. Best Matches usually have unique names in comparison to other mismatched forms, and the caps of Full Bottles indicate what Full Bottle is its Best Match.

Devices

 * Build Driver - Transformation device.
 * Full Bottles - Transformation trinkets.
 * BuildPhone - Build's personal smartphone that can transform into the Machine Builder.

Weapons

 * Drill Crusher - Build's personal drill-like weapon.
 * 4 Koma Ninpogatana - Build NinninComic's personal weapon.
 * Hawk Gatlinger - Build HawkGatling's personal weapon.
 * Kaizoku Hassha - Build KaizokuRessha's personal weapon.

Vehicles

 * Machine Builder - Build's personal Rider Machine that is transformed from the BuildPhone.

Portrayal
Sento Kiryu is portrayed by Atsuhiro Inukai (犬飼 貴丈). As Kamen Rider Build, his suit actor is Seiji Takaiwa (高岩 成ニ) and Yuya Nawata (縄田雄哉, Nawata Yuya) in his televised debut in the 44th episode of Kamen Rider Ex-Aid.

Etymology
The kanji used to spell his name, Sento (戦兎), is composed of the first kanji for tank (戦車) and the kanji for rabbit (兎).

Appearances

 * Icon-exaid.png Kamen Rider Ex-Aid
 * Episode 44: The Last Smile
 * Kamen Rider Ex-Aid: True Ending
 * Icon-build.png Kamen Rider Build
 * Episode 1: The Best Match One
 * Icon-exaid.png Icon-build.png Kamen Rider Heisei Generations: FINAL