This article is about a/an rider in Kamen Rider Build.
Note: This exists as a soft redirect to avoid spoiling viewers without warning. For his current identity, click here (spoilers at your own risk).

"Kamen Rider Build. Build as in 'Create' or 'To form'."
―Takumi's interpretation of Kamen Rider Build[src]

"See You!"
―Takumi's catchphrase when he is about to leave[src]

"Do you still believe in your friends? Then show me the future that you'll build."
―Takumi as he fully assimilates with Sento.[src]

Takumi Katsuragi (葛城 巧 Katsuragi Takumi) was a researcher at Touto Institute of Advanced Matter Physics who was murdered by Soichi Isurugi/Evolto upon discovering his true identity. Known among his colleagues as The Devil's Scientist (悪魔の科学者 Akuma no Kagaku-sha), 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 initially had memory of his past. Takumi's memories would later resurface alongside his new identity's memories.

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. He presented the idea to Gentoku, who blatantly rejected the ideas of human experimentation, but Takumi insisted it was for the sake of science. Behind Gentoku's back, he began his experiments, only to be caught and fired by Gentoku.

However his firing was only a ploy to evade him from the law as Gentoku re-approached and scouted him to join Faust, a organization funded by Namba Heavy Industries Ltd. for the sole purpose of continuing the covert human experimentations Takumi started. He was placed as head of the research team, and was successful in creating the Smash, Transteam Gun in a matter of months. ROGUE The Devil's Scientist

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

World of Ex-Aid

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

In the years before his death, Takumi was chosen to work alongside Kaisei Mogami on his parallel research studies. Together they build the Enigma that would allow Takumi to to visit the World of Ex-Aid on two separate occasions as Kamen Rider Build. Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders

First Visit

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

Second Visit

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. However Parado did not return in the same area as Build, where he would spend the next two years attempting to track him down. 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


Katsuragi prepares to henshin

Katsuragi confronts Evolto.

"You had me fooled, but I'm prepared now. Now, I will stop you!"
―Katsuragi to Evolto[src]

At some point, Katsuragi discovered the true identities of both Soichi Isurugi and Ryuga Banjo and wanted to destroy them upon learning of Blood Stalk's malicious goals. Formulating a plan so that Ryuga would come by, Katsuragi confronted Blood Stalk saying he plans on leaving Faust and would never obey Evolto's orders or reveal the location of the Evol-Driver. He attempted to transform into Build GorillaMond, however his Build Driver was switched out, resulting in his Gorilla FullBottle reverting back to an Empty FullBottle, rendering him unable to transform. Evolto then knocked Katsuragi out on the spot. Ironically, Taro Satou just so happened to have arrived and get frightened by Stalk’s appearance, only for the latter to kill Taro, and switching their faces and clothing. One hour later, Ryuga Banjo would arrive following Katsuragi's plan (although it had already failed by the time he arrived) and be framed as Katsuragi's murderer, thus he was sent to prison.


Main article: Sento Kiryu

With his face altered and memories wiped, Takumi Katsuragi became Sento Kiryu.

Shingo Kuwata has exclaimed to Sento Kiryu 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?

Shortly before the Enigma crisis, Sento recalled the memory of Katsuragi's encounter with Ex-Aid in a dream, leading him to discover the Fullbottle that Katsuragi had acquired. As yet unaware of his connection to Build's creator, Sento insisted he was the victim of mistaken identity when confronted by Parado. Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders

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

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

After the revelation that Takumi's father Shinobu Katsuragi was the one who experimented on Ryuga Banjo as a child, the truth came back to haunt Sento Kiryu.

After Sento was released by Evolto, he regained the memories of his former identity while losing those of his current one. As Takumi awoke to Ryuga Banjo standing over him, he revealed his identity to him. The Ultimate Phase.

Resurfacing with Takumi's memories, he is surprised that Evolto has reached his final form and watches the other Riders fight Evolto again. Shortly however, Gentoku realized that they were outpowered and forced the entire team to retreat back to nascita.

Back at nacita, Takumi is overwhelmed by his new look and continuously wonders how this was even scientifically possible. He began to scribble over his marker board while overhearing the others discussing his nickname "The Devil's Scientist", saying "devil" was uncalled for. He recognized Misora Isurugi as the girl whom he had purifying Fullbottles for while he was with Faust, all in the name of science. Takumi began to wonder why Ryuga Banjo was helping him, despite him having Evolto's DNA, and believes that even if the DNA was gone, Evolto could still awaken inside.

Takumi is called out to talk by Gentoku Himuro, and the two exchange words on how Gentoku mad misused the Rider System for war. Gentoku apologized and said the Pandora Box altered his mindset, but Takumi didn't want to hear excuses since it was undeniable that it was them both that were responsible for the war. Takumi knew that even though Gentoku wanted to use the Kamen Riders for war, he convinced himself it was solely to stop Evolto's upcoming attack, and that the sacrifices made were necessary. In the end, Takumi walks away, saying he never should have trusted Gentoku.

Later, the team enter Evolto's space of creation to help Utsumi on his request to stop Evolto. However, Takumi is unable to keep up with Build RabbitRabbit form as it was too high-performance for him. Evolto comments that Takumi will never be able to use the latest version of Build, but Takumi proclaims that he can and he will, because he built Build for the sole purpose of beating Evolto. Takumi attempts to use the Pandora Box panel, but is froze still by the electrical output of it. Evolto takes this chance to punch him back and force him out of his transformation. Evolto takes the later chance to kill both Rai Washio and Fu Washio, thus Takumi becomes angry to see lives being lost in front in him. Evolto hands Utsumi a Evol Driver and he transforms into Kamen Rider Mad Rogue, where he fights Gentoku. Gentoku is defeated and Grease arrives in the nick of time to help the team escape. Mad World

Back at nascita, the team pounders on what to do now that Evolto has voiced his intent to take over the country for himself, and they want to investigate why Evolto now wants to rule a planet rather than destroy it. Takumi wishes to complete the new power-up item to defeat Evolto, along with Ryuga, who is beginning to have episodes of Evolto's memories surfacing in him. Later that night, Takumi completes the Genius Bottle and is confident he can defeat Evolto and Ryuga. Misora berates him for not believing in his friends, but Takumi said friends can only lead to distrust and betrayal. The next day, Takumi hears Gentoku regretting his actions in the past and wants to make it up and asks the team to believe in him.

Takumi heads out to "help" Cross-Z and Grease with RabbitRabbit Form, now modified to fit his specs, and easily defeats the Clone Smash. He fights MadRogue to an equal standstill, but is knocked back when Utsumi questions his motives for science. Takumi reveals the Genius Bottle and tries to use it, but it wouldn't activate. Theoretically, he should be able to use it, but Takumi didn't know why he couldn't, as MadRogue attacks him and forces him out of his transformation. Ryuga arrives to fight MadRogue and tells Takumi that Sento fought for justice and was the epitome of a superhero, traits that Takumi didn't have. Watching MadRogue force Ryuga out of Rider form, Takumi experiences a flow of memories coming into his mind. Takumi then appears in front of Sento, and askes him if he believed in the power of trust and friendship. Sento responds with a smile, and Takumi asks Sento to show him the future he can build. Takumi and Sento join hands, and the two assimilate with each other into Sento.The Unstoppable Genius

Katsuragi meets Sento

Katsuragi and Sento face to face.


Takumi Katsuragi

Takumi during a human experimentation

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.

He also claims to be a pacifist when he was battling Genm. This was due to his reasons behind the Build System and his views towards its use after his identity was changed.

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. However, it was revealed the reason why he created the Rider System in the first place was to defeat Evolto, and was appalled to hear Gentoku used it to instigate the Japanese Civil War.

Misora also pointed that Katsuragi, after his memories are restored, behaves just like Sento. But, the difference is that he is arrogant and dismissive to a fault, as he lacks the understanding of friendship of others, comparing that from a shōnen manga. Katsuragi also uses honorifcs in his sentences unlike Sento, who speaks using slang. While desperate in his objective to defeat Evolto, he doesn't seem to express any concern about killing Banjo because of his connection with the alien lifeform. 


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? (Techno rock music) 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, Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders (flashback)

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? (Tropical rock music) 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

By using the FullFull RabbitTank Bottle alongside the Hazard Trigger, Build can upgrade the sleek, black Hazard Form into either RabbitRabbit Form or TankTank Form. The FullFull RabbitTank Bottle was designed to give Build an immense power boost over Hazard Form while suppressing the stimulus overflow that causes Build to go berserk. Build's weapon in these forms is the Fullbottle Buster.

The ending theme for both RabbitRabbit Form and TankTank Form is entitled "Ready Go!!".

RabbitRabbit Form

RabbitRabbit Form

"Rabbit and Rabbit! Build up! Are you ready? Overflow! (Techno pop music) Kurenai no speedy jumper! RabbitRabbit! Yabei! Haei!"
―Transformation announcement[src]

Rider Statistics

  • Rider Height: 197.5 cm
  • Rider Weight: 106.2 kg

Ability Parameters:

  • Punching Power: 39.9 tons
  • Kicking Power: 47.8 tons
  • Jump Height
    • Base Jump Height: 88.0 m
    • Max Jump Height: 132.0 m
  • Running Speed
    • Base Running Speed: 100 m. per 1.2 sec.
    • Maximum Running Speed: 100 m. per 0.8 sec.

RabbitRabbit Form (ラビットラビットフォーム Rabitto Rabitto Fōmu) is one of Build's upgraded super forms, based on the Rabbit Halfbody. It is accessed by upgrading RabbitTank Hazard Form with the FullFull RabbitTank Bottle, set to its Rabbit mode, hence known as the Crimson Speedy Jumper (紅のスピーディージャンパー Kurenai no Supīdī Janpā).

In this form, Build can not only run faster, and jump higher than he could in RabbitTank Sparkling form, but he can also stretch his limbs at will. Strengthening materials inside the chest piece of RabbitRabbit allow the user to increase its reaction time, jumping height, running speed up to a maximum of 1.5x.

In RabbitRabbit Form, Build is armed with and protected by the Rapid Rabbit Shoulders (BLDラピッドラビットショルダー BLD Rapiddo Rabitto Shorudā), the Speed Chest Armor (スピーディーチェストアーマー Supīdī Chesuto Āmā), the arm-mounted Hop Pop Gauntlets (ホップポップガントレット Hoppu Poppu Gantoretto) and the leg-mounted Jump Champ Leggers (ジャンプチャンプレガース Janpu Chanpu Regāsu).

The Hop Pop Gauntlets and Jump Champ Leggers contain Dimension Springers (ディメンションスプリンガー Dimenshon Supuringā) that enable long-distance stretching.

On the back of RabbitRabbit Form is the cape-like Mufflerabbit Accelerator (マフラビットアクセラレーター Mafura Bitto Akuserarētā), which enables Build to run around at supersonic speeds thanks to an inbuilt propulsion accelerating device.

Unlike his alternate identity, Katsuragi cannot access the full capabilities of this form, and can easily be knocked out of transformation. However, once he retrofitted the FullFull RabbitTank Bottle to match his specs, Takumi now could access the full capabilities of this form.

  • Build Driver finisher:
    • RabbitRabbit Finish (ラビットラビットフィニッシュ Rabitto Rabitto Finisshu): Jumping into the air, Build stretches his leg towards the opponent, and pulling his body towards his foot, connects with the target, with the resulting impact sending his opponent flying.
  • Fullbottle Buster finisher:
    • Fullbottle Break (フルボトルブレイク Furubotoru Bureiku): Build channels the power of a single Fullbottle for either a powerful slash or a powerful shot.
      • Buster Cannon Mode
        • Organic
          • Rabbit: Build fires a ball of red energy at the enemy.
    • Just Match Break (ジャストマッチブレイク Jasuto Matchi Bureiku): Build channels the power of two Fullbottle for either a powerful slash or a powerful shot.
      • Buster Cannon Mode
        • Organic
          • Rabbit + Panda: Build fires a ball of red and white energy mixed together.
        • Inorganic
    • Miracle Match Break (ミラクルマッチブレイク Mirakuru Matchi Bureiku): Build channels the power of three Fullbottle for either a powerful slash or a powerful shot.
      • Buster Cannon Mode
        • Organic
          • Rabbit + Panda + Taka: Build fires a ball of red and white energy mixed together that gives off orange energy shockwaves upon impact.
    • Ultimate Match Break (アルティメットマッチブレイク Arutimetto Macchi Bureiku): Build channels the power of four Fullbottle for either a powerful slash or a powerful shot.
    • FullFull Match Break (フルフルマッチブレイク Furu Furu Matchi Bureiku): Build channels the power of the FullFull RabbitTank Bottle for either a powerful slash or a powerful shot.
      • Buster Blade Mode
        • Rabbit Mode: Build runs at the enemy at high speeds, and delivers a circular slash with the blade covered in red energy.

Appearances: Build Episodes 38, 39




Handheld weapons:

  • Fullbottle Buster - Build's personal sword-like and pump-action shotgun-like weapon, accessed by any form that uses the FullFull RabbitTank Bottle.

Suit-equipped weapons:

  • Rabbit Foot Shoes - Build's rabbit-like spring shoe accessed by any form that uses the Rabbit Fullbottle.
  • Tank Roller Shoes - Build's tank-like tread shoe accessed by any form that uses the Tank Fullbottle.
  • Muscle Glove - Build's gorilla-like gauntlet accessed by any form that uses the Gorilla Fullbottle.
  • BLD Prism Glove - Build's diamond-like glove accessed by any form that uses the Diamond Fullbottle.

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.
    • However, the Build Driver announces Best Matches, something which was not possible until Sento himself modified the Driver to do so. This error is likely due to promotional purposes, to promote the Rider succeeding Ex-Aid at the time.
  • In addition to RabbitTank, Katsuragi has been observed to have a preference for GorillaMond Form, which he used in both his on-screen appearances as Build in Ex-Aid, as well his failed transformation against Evolto.
  • When Katsuragi refers to himself, he uses both honorifics, "boku" and "ore", at the same time. This is a similar trait found in his predecessor Emu Hojo, though Emu normally uses "boku" and only uses "ore" as the Genius Gamer M under the influence of Parado.