Takumi Katsuragi


 * Note: This exists as a soft redirect to avoid spoiling viewers without warning. For his current identity, click here (spoilers at your own risk).

Takumi Katsuragi (葛城 巧) was a researcher at Touto Institute of Advanced Matter Physics who was murdered by Soichi Isurugi upon his intended defection from Faust, an organization he founded. Known among his friends as The Devil's Scientist (悪魔の科学者), he is the infamous creator of the Build Driver, the Fullbottles, the Sclash Driver, the Sclashjellies and the Transteam system.

It is later revealed that he is in fact, still alive, under the identity of a different person who has no memory of his past.

Life
The son of teacher Kyoka Katsuragi and researcher Shinobu Katsuragi, Takumi was a brilliant prodigy and among one of the best researchers at the Touto Institute of Advanced Matter Physics. Infamously called the "Devil's Scientist", the nickname stems from his extensive notes on the Pandora Box, as well as the mysterious Nebula Gas. As part of his Project Build, he harnessed the Nebula Gas and created the Fullbottles, and the Build Driver to filter out the raw power of the bottles without the dangers of becoming Smash. To find suitable candidates for the Build Driver, which was to be mass-produced for warfare, he founded the Faust organization in order to covertly engage in human experimentation, to see who was capable of not becoming Smash to use the Build Drivers.

He would later entrust Project Build's research to his mother.

"Death"
At some point Katsuragi wanted to quit Faust, and Stalk confronted him about it. However, Taro Satou just so happened to have arrived, so Stalk knocks Katsuragi out, kills Taro, switching their faces and clothing. One hour later, Soichi calls in Ryuga Banjou as the murderer, which prompted Guardians to investigate and hopefully capture the assailant. At that same time, Ryuga had just arrived at the apartment and found "Katsuragi" dead, thus the act was blamed on him and he was sentenced to prison.

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

- Build to Genm

It is revealed that, before Takumi's supposed murder, he had visited the World of Ex-Aid on two separate occasions as Kamen Rider Build. 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 Form 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 Kuroto.

Inspired by this encounter, Kuroto created a Rider Gashat based on Build, the latest in his collection of those of the Heisei Riders, which Emu Hojo snatched from his hand and activated. In next occasion, Build successfully encountered Emu and absorbed Ex-Aid's essence into a Fullbottle. This led Emu to lose the ability to transform, with Parado following Build back into his native world in an attempt to track him down and get Emu's powers back. When Parado eventually confronted Sento Kiryu, the current Build, Sento claimed to have no recollection of the event, thinking of it as a dream.

Legacy
Shingo Kuwata has exclaimed to Build that Takumi Katsuragi is, in fact, still alive.

He had been accused of being the true identity of Blood Stalk, which was later proven false.

It is later revealed that he is still alive as Sento Kiryu, with the dead "Takumi" actually being a man named Taro Satou.

Making his debut as Kamen Rider Rogue, Gentoku Himuro addressed Sento as Katsuragi.

Personality
As a researcher, Takumi has no qualms going to any lengths to complete his research, even going so far as to use brutal methods such as human experimentation. Takumi himself claimed that he'll gladly sell his soul to devil, as long as science evolves even further. However, he is shown to still have a filial side towards his mother, although he does not seem to express it on the outside.

Eventually, it was revealed that his commitment to Faust's goals eventually wavered enough for Blood Stalk to consider him a traitor, and orchestrated the events that lead to his new identity and him gathering Fullbottles.

Devices

 * Build Driver - Transformation device.
 * Fullbottles - Transformation trinkets.
 * Fullbottle Holder - Carrier strap for Build's Fullbottles

Portrayal
Takumi Katsuragi is portrayed by Yukiaki Kiyama (木山廉彬). In Kamen Rider Ex-Aid media he was voiced by Atsuhiro Inukai (犬飼貴丈) who plays his current identity Sento Kiryu. As Kamen Rider Build, his suit actor is Yuya Nawata (縄田 雄哉) in his televised debut in the 44th episode of Kamen Rider Ex-Aid.