This article is about a/an rider in Kamen Rider Build.
Takumi Katsuragi
Takumi Katsuragi (Build)
Kamen Rider Build
Gender: Male
Aliases: The Devil's Scientist
Series: Kamen Rider Build
Rider Type: Unknown
Affiliation: Touto Institute of Advanced Matter Physics (Former)
Faust (Founder)
Homeworld: Earth (World of Build)
First Appearance: Kamen Rider Ex-Aid: True Ending (production-wise)
The Last Smile (Chronological)
Last Appearance: TBA
Number of Episode
1 (Ex-Aid)
TBA (Build)
TBA (Movies)
Full list of appearances
Actor: Yukiaki Kiyama
Atsuhiro Inukai (Voice in Ex-Aid)
Kamen Rider Build
Build 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 Katsuragi Takumi) was a researcher at Touto Institute of Advanced Matter Physics who was supposedly murdered by Soichi Isurugi. Known among his friends as The Devil's Scientist (悪魔の科学者 Akuma no Kagaku-sha), he is the founder of Faust and the 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.

Character History

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. The Trap of Project Build 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. The Devil's Scientist

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

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.

Shingo Kuwata has exclaimed to Build that Takumi Katsuragi is, in fact, still alive. The Trap of Project Build

He had been accused of being the true identity of Blood Stalk Technology of Destruction, which was later proven false. Who Takes Off The Veil?

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

Other Appearances

"You know, in spite of how it may seem, I'm actually a pacifist."
―Build to Genm[src]

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. Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders

Build murdering

Build accidently killed Genm.

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. The Last Smile

Inspired by this encounter, Kuroto created a Rider Gashat based on Build, the latest in his collection of those of the Heisei Riders, Kamen Rider Ex-Aid "Tricks": Kamen Rider Genm which Emu Hojo snatched from his hand and activated. Endless Game

Katsuragi sucking

Build absorbing Ex-Aid's essence into a Fullbottle.

In next occasion, Build successfully encountered Emu and absorbed Ex-Aid's essence into a Fullbottle. Kamen Rider Ex-Aid: True Ending 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. Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders


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. However, he is shown to still have a filial side towards his mother, although he does not seem to express it on the outside.


In any form that uses the Rabbit Fullbottle, Build is armed with the Rabbit Foot Shoes (ラビットフットシューズ Rabitto Futto Shūzu) on his left leg for increased jumping, and can summon the Drill Crusher.

RabbitTank Form

RabbitTank Form

"Rabbit! Tank! Best Match! Are you Ready? Hagane no Moonsault! RabbitTank! Yeahhh!"
―RabbitTank's transformation announcement[src]

Rider Statistics

  • Rider Height: 196.0 cm
  • Rider Weight: 99.0 kg

Ability Perimeters:

  • Punching Power: 9.9 tons (right arm)/17.0 tons (left arm)
  • Kicking Power: 23.7 tons (right leg)/17.8 tons (left leg)
  • Maximum Jump Height: 55.0 m
  • Maximum Running Speed: 100 m. per 2.9 sec.

RabbitTank Form (ラビットタンクフォーム Rabitto Tanku Fōmu) is Build's red and blue primary and default Best Match form form accessed from the Rabbit and Tank Fullbottles, hence known as the Moonsault of Steel (鋼のムーンサルト Hagane no Mūnsaruto). It is themed after a rabbit and a tank.

RabbitTank is considered to be the most well balanced; having a good amount of power and agility in all of his Ability Perimeters, thus making it Build's default form, despite it being capable of initiating transformation with any set of Build's Fullbottles. This is also Build's second fastest form.

In this Best Match form, Build is armed with the Tank Roller Shoes (タンクローラーシューズ Tanku Rōrā Shūzu) on his right leg for kicking attacks, and can also act as a working tread to roll along on a flat foot.

This form's weapon is the Drill Crusher.

As a Best Match, this form has two finishers:

  • Build Driver finisher:
    • Vortex Finish (ボルテックフィニッシュ Borutekku Finisshu): Build dives underground to send a white energy chart flying up to the surface with the dotted line securing the enemy before leaping back up, and delivering a kick whilst riding the chart's line. According to Blood Stalk, this finisher has a Hazard Level of 3.2, and then 3.7 when Build attacks him out of anger.
  • Drill Crusher finisher:
    • Vortex Break (ボルテックブレイク Borutekku Bureiku):
      • Blade: Build channels the energy of a Fullbottle in his Drill Crusher and performs a powerful slash.
        • Rabbit: The Drill Spiral Blade spins such that it creates an energy whirlpool before Build performs a red energy slash.
        • Ninjya: Purple energy Drill Spiral Blades are projected and spin violently around the Drill Crusher.
      • Gun: Build channels the energy of a Fullbottle in his Drill Crusher and performs a powerful blast.
        • Harinezumi: Build shoots white energy spikes at the enemy.

Appearances: Ex-Aid Episode 44, True Ending

In any form that uses the Gorilla Fullbottle, Build is armed with the Muscle Glove (マッスルグローブ Massuru Gurōbu) on his right arm for enhanced punching.

GorillaMond Form

GorillaMond Form

"Gorilla! Diamond! Best Match! Are you Ready? Kagayaki no Destroyer! GorillaMond! Yeahhh!"
―GorillaMond's transformation announcement[src]

Rider Statistics

  • Rider Height: 189.0 cm
  • Rider Weight: 112.0 kg

Ability Perimeters:

  • Punching Power: 25.9 tons (right arm)/15.8 tons (left arm)
  • Kicking Power: 17.3 tons (right leg)/16.5 tons (left leg)
  • Maximum Jump Height: 32.5 m
  • Maximum Running Speed: 100 m. per 8.4 sec.

GorillaMond Form (ゴリラモンドフォーム Goriramondo Fōmu) is Build's brown and cyan second Best Match form accessed from the Gorilla and Diamond Fullbottles, hence known as the Shining Destroyer (輝きのデストロヤー Kagayaki no Desutoroyā). It is themed after a gorilla and a diamond.

In this Best Match form, Build is armed with the BLD Prism Glove (BLDプリズムグローブ BLD Purizumu Gurōbu) on his left hand.

GorillaMond shows an increase in power, as the Punching Power of Build is significantly higher than in RabbitTank, albeit with a slightly decreased amount in its left arm, but it lacks Kicking Power and agility compared to RabbitTank. His left arm can convert inorganic objects, or even weakened enemies, into diamonds.

As a Best Match, this form's finisher is the Vortex Finish (ボルテックフィニッシュ Borutekku Finisshu): This finisher has two variations:

  • Build uses the BLD Prism Glove creates a gust full of diamonds and uses the Muscle Glove to punch them at the enemy. The diamond then creates a tornado that causes a human to separate from his/her Smash form, then Build punches the Smash inside the tornadoes, thereby defeating the Smash.
  • Build stops an enemy's projectile attack in mid-air with the BLD Prism Glove, altering the projectiles' atomic structure into a diamond shield. He then punches the shield with the Muscle Glove, shattering it and sending the shards flying at the enemy at high speeds.

Appearances: Ex-Aid Episode 44, True Ending



Behind the Scenes


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


  • Him being the founder of Faust and at the same time being called the Devil's Scientist alludes to titular character of the namesake German tale in which the organization he founded is named after; a scholar who made a pact to the Devil exchanging his soul for unlimited knowledge and worldly pleasures.
  • He is similar to Kuroto Dan from the previous season as both were the founders/creators of the villain factions of the series as well as the creators of the protagonists' Kamen Rider powers.
    • Just like Kuroto, Katsuragi debuted in his series' predecessor but in his respective Kamen Rider identity and he wasn't played by his actor. Katsuragi also cared for his mother despite being a villain, similar to Kuroto. But unlike Kuroto, Katsuragi had a change of heart and became good.
  • In Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders, it is revealed that he is the true identity of the Build who encountered Kamen Riders Genm and Ex-Aid. This was teased in a TV spot following the premiere of the film.
    • However, his usage of the GorillaMond Form creates a continuity error as the form's respective Fullbottles were only created by Sento Kiryu after he became Build. Also, the Build Driver announces Best Matches, something which was not possible until Sento himself modified the Driver to do so. These errors are likely due to promotional purposes, to promote the Rider succeeding Ex-Aid at the time.



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