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 no memory of his past. Takumi's memories would later resurface alongside his new identity's memories.

Character History

Early Life

Takumi Katsuragi was born to Kyoka Katsuragi and researcher Shinobu Katsuragi. In his youth, Takumi was considered a brilliant prodigy and would often mess around with his hair, as his father often said. Sometime during grade school, his father posed a question as to whenever he would join him in preventing an alien invasion should it happen, and Takumi said yes.

During the Sky Wall Disaster, Takumi was bewildered to see Shinobu be one of the main causes of it, and asked why his father did it. He said it was for "love and peace", which Takumi, later Sento Kiryu use as his main inspiration for fighting.

Takumi later received a job at the Touto Institute of Advanced Matter Physics shortly after his father's death, but was unaware that his father was actually still alive at the time. Taking up his father's research on the Project Build, Takumi was revered as one of the best researchers at the institute, and was infamously nicknamed the "Devil's Scientist", due to his extensive notes on the Pandora Box, as well as the mysterious Nebula Gas. As part of the project, he continued the development of 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 accidentally "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 of him. Evolto hands Utsumi a Evol Driver and he transforms into Kamen Rider MadRogue, 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, and 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.

Katsuragi meets Sento

Katsuragi and Sento face to face.

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 he lacked heart and compassion. Sento on the other hand, fought for justice and was the epitome of a superhero, traits that Takumi didn't have and lacked with over the years with his mind. Watching MadRogue force Ryuga out of Rider form, Takumi experiences a flow of Sento's memories coming into his mind. Takumi then appears in front of Sento, and asks him if he believed in the power of trust and friendship, regardless of whoever's sins had been done. Sento responds with a smile, and Takumi asks Sento to show him the future he can build, better than he ever did in the past. Takumi and Sento then join hands, and the two assimilate with each other into Sento. The Unstoppable Genius

Even after his assimilation with Sento, Takumi continues to exist in form of memories inside his new persona's psyche, talking and discussing with him the matters that Sento can't remember himself: the Lost Bottles and the false death of Shinobu Katsuragi. The Final Revolution The Truth of the Best Match

As Sento continued to research on Shinobu and with the appearance of another Build, Takumi starts to doubt his father's actions as Sento and he spoke inside their memory world. Legacy of DoubtAnother BuildThe End of EvoltoThe Scientist of Hope

After Evolto's defeat, as Sento observes the new world he created, Takumi finally bids farewell to Sento, disappearing from his new persona's psyche. The Tomorrow Build Will Create

Kamen Rider Zi-O


Takumi meets Zi-O

Main article: Sento Kiryu#Timeline Disruption

As a result of the creation of Another Build by Time Jacker Heure, Kamen Rider Build's history was erased. In the new timeline, Takumi never worked on the Build Rider System and never encountered Evolto, and so never became Sento Kiryu.

After the temporary defeat of Another Build in 2018, Takumi and Ryuga regain their memories and entrust Sougo Tokiwa with Build and Cross-Z Ridewatches. After Another Build's permanent defeat, he permanently loses his memories. Best Match 2017

Later, due to another time disturbation by Super Time Jacker Tid, Takumi regains his memories and he, along with Ryuga, Kazumi, and Gentoku aids Sougo against Another Kuuga. Kamen Rider Heisei Generations FOREVER

Kamen Rider Grease

Due to the merging of the two worlds, this version of Takumi Katsuragi, along with his father, exists in the new world.


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. 


Takumi's Build Driver did not originally announce Best Matches, but was modified to do so by Sento Kiryu after Takumi's supposed death.

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

"Rabbit! Tank! Are you ready? RabbitTank!"
―Original transformation announcement[src]

"Rabbit! Tank! Best Match! Are you ready? (Techno rock music) Hagane no moonsault! RabbitTank! Yeahhh!"
―Transformation announcement after Sento's modifications[src]


RabbitTank Form

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's finisher is the Vortex Finish (ボルテックフィニッシュ Borutekku Finisshu).

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

"Gorilla! Diamond! Are you ready? GorillaMond!"
―Original transformation announcement[src]

"Gorilla! Diamond! Best Match! Are you ready? (Tropical rock music) Kagayaki no destroyer! GorillaMond! Yeahhh!"
―Transformation announcement after Sento's modifications[src]


GorillaMond Form

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): Build uses the BLD Prism Glove to create a pile of diamonds, then punches it with the Muscle Glove, sending the diamonds flying at the enemy.

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.

  • This form has two finishers
    • Build Driver finisher:
    • Fullbottle Buster finishers:
      • 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 a powerful attack
        • Buster Blade Mode
          • Rabbit Mode: Build performs a 360 degree spinning slash covered in red energy that is capable of hitting multiple enemies.

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.

Legend Rider Devices


Kamen Ride: Build

"Kamen Ride: Build! Hagane no Moonsault! RabbitTank! Yay!"
―Transformation announcement[src]

With the Build Rider Card, Decade can transform into Kamen Rider Build's RabbitTank Form.

"Kamen Ride: Build! Genius! Kanzen Muketsu no Bottle Yarou! Build Genius! Sugei! Monosugei!"
―Transformation announcement[src]
Genius Card

Final Kamen Ride: Build Genius Form

Final KamenRide: Build Genius Form: This card can be used in Decade's Neo Decadriver to transform into Build Genius Form.

Kamen Rider Build Gashat

Rider Gashat

Kamen Rider Build (仮面ライダービルドガシャット Kamen Raidā Birudo Gashatto): Though it was used by Kamen Riders Brave, SnipeLazer Turbo and Genm to protect their Gamer Drivers from the effects of the Enigma and both Kuroto Dan and Emu Hojo also used this gashat in their Gashacon Breakers against Nebula Bugsters in Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders, there does not seem to be any indication of a Legend Rider form associated with this Gashat.

"(Digital beeping) Build!"
―Activation announcement[src]

"Best Match! The genius Rider who transforms with Fullbottles is... (Clock ticking noise) Build! (ベストマッチ!フルボトルで変身する天才ライダーは…ビルドだ! Besuto Matchi! Furubotoru de henshin suru tensai Raidā wa… Birudo da!)"
―Secondary activation announcement[src]

"Rider Time! (RabbitTank-esque rock music) Best Match! Build!"
―Transformation announcement in the Ziku-Driver's right-hand slot[src]

"(Right-hand Ridewatch's announcement)! Armor Time! (RabbitTank-esque rock music) Best Match! Build!"
―Rider Armor transformation announcement[src]

"Finish Time! Build! Vortex Time (Break/Burst)!"
―Rider Armor finisher announcement[src]

Build Ridewatch (ビルドライドウォッチ Birudo Raidowotchi): Based on Kamen Rider Build RabbitTank Form, this Ridewatch provides access to the BuildArmor used by Zi-O or Geiz. It is dated 2017.

It was manifested by Sento Kiryu from a Blank Watch given by Sougo Tokiwa.

"(Digital beeping) Sparkling!"
―Activation announcement[src]

"Power bursts from the power of Pandora! Build RabbitTank Sparkling! (パンドラの力ではじけるパワー!ビルドラビットタンクスパークリング! Pandora no chikara de hajikeru pawā! Birudo RabittoTanku Supākuringu!)"
―Secondary activation announcement[src]

"(Right-hand Ridewatch's announcement)! Armor Time! (soda can opening noise with fizzes) RabbitTank Sparkling!"
―Transformation announcement in the Ziku-Driver's left-hand slot[src]

"Finish Time! Build! Vortex Time (Break/Burst)!"
―Finisher announcement in left-hand slot[src]

Build RabbitTank Sparkling Ridewatch (ビルドラビットタンクスパークリングフォームライドウォッチ Birudo RabittoTanku Supākuringu Fōmu Raidowotchi): Based on Kamen Rider Build RabbitTank Sparkling Form, this Ridewatch provides access to the BuildRabbitTankSparklingArmor. It is dated 2017.

"(Digital beeping) Hazard![1]"
―Activation announcement[src]

"Oh no! The jet black rampaging warrior, RabbitTank Hazard! (ヤッベーイ!漆黒の暴走戦士、ラビットタンクハザード! Yabbēi! Shikkoku no bōsō senshi, RabittoTanku Hazādo!)[1]"
―Secondary activation announcement[src]

"Rider Time! (Hazard Form's transformation music) Yabei! Hazard!"
―Transformation announcement in the Ziku-Driver's right-hand slot[src]

"(Right-hand Ridewatch's announcement)! Armor Time! (Hazard Form's transformation music) Yabei! Hazard!"
―Rider Armor transformation announcement[src]

"Finish Time! Build! Hazard Time (Break/Burst)!"
―Rider Armor finisher announcement[src]

Build RabbitTank Hazard Form Ridewatch (ビルドラビットタンクハザードフォームライドウォッチ Birudo RabittoTanku Hazādo Fōmu Raidowotchi): Based on Kamen Rider Build RabbitTank Hazard Form, this Ridewatch provides access to the BuildRabbitTankHazardFormArmor. It is dated 2017.

"(Digital beeping) RabbitRabbit!"
―Activation announcement[src]

"Super speed! Super jump! Build RabbitRabbit Form! (超スピード!超ジャンプ!ビルドラビットラビットフォーム! Chō supīdo! Chō janpu! Birudo RabittoRabitto Fōmu!)"
―Secondary activation announcement[src]

"(Right-hand Ridewatch's announcement)! Armor Time! (Techno pop music with tbe Rabbit robot hopping around) Haei! RabbitRabbit!"
―Transformation announcement in the Ziku-Driver's left-hand slot[src]

"Finish Time! Build! RabbitRabbit Time (Break/Burst)!"
―Finisher announcement in left-hand slot[src]

Build RabbitRabbit Form Ridewatch (ビルドラビットラビットフォームライドウォッチ Birudo RabittoRabitto Fōmu Raidowotchi): Based on Kamen Rider Build RabbitRabbit Form, this Ridewatch provides access to the BuildRabbitRabbitFormArmor. It is dated 2017.

"(Digital beeping) TankTank!"
―Activation announcement[src]

"Super armor! Super weight! Build TankTank Form! (超装甲!超重量!ビルドタンクタンクフォーム! Chō sōkō! Chō jūryō! Birudo TankuTanku Fōmu!)"
―Secondary activation announcement[src]

"(Right-hand Ridewatch's announcement)! Armor Time! (Techno rock music) Tuei! TankTank!"
―Transformation announcement in the Ziku-Driver's left-hand slot[src]

"Finish Time! Build! TankTank Time (Break/Burst)!"
―Finisher announcement in left-hand slot[src]

Build TankTank Form Ridewatch (ビルドタンクタンクフォームライドウォッチ Birudo TankuTanku Fōmu Raidowotchi): Based on Kamen Rider Build TankTank Form, this Ridewatch provides access to the BuildTankTankFormArmor. It is dated 2017.

"(Digital beeping) Genius!"
―Activation announcement[src]

"Very amazing! The super-genius Rider full of bottles! Build Genius Form! (モノスゲーイ!ボトルだらけの超天才ライダー!ビルドジーニアスフォーム! Monosugēi! Botoru darake no chō tensai Raidā! Birudo Jīniasu Fōmu!)"
―Secondary activation announcement[src]

"Rider Time! (Genius Form's transformation music) Chou Tensai! Build Ge~ius! Genius!"
―Transformation announcement in the Ziku-Driver's right-side slot[src]

"Armor Time! (Genius Form's transformation music) Chou Tensai! Build Gen~ius! Genius!"
―Transformation announcement[src]

"Finish Time! Build! Genius Time (Break/Burst)!"
―Finisher announcement[src]

Build Genius Form Ridewatch (ビルドジーニアスフォームライドウォッチ Birudo Jīniasu Fōmu Raidowotchi): Based on Kamen Rider Build Genius Form, this Ridewatch provides access to the BuildGeniusFormArmor. It is dated 2017[1], but shown on the Ziku-Driver's screen as FIN.

"(Digital beeping) RabbitDragon!"
―Activation announcement[src]

"The gold rabbit! The silver dragon! Build RabbitDragon! (金のラビット!銀のドラゴン!ビルドラビットドラゴン! Kin no rabitto! Gin no doragon! Birudo RabittoDoragon!)"
―Secondary activation announcement[src]

"Armor Time! (RabbitTank-esque rock music) Rabbit! Dragon! RabbitDragon!"
―Transformation announcement[src]

"Finish Time! Love & Peace Time (Break/Burst)!"
―Finisher announcement[src]

Build RabbitDragon Form Ridewatch (ビルドラビットドラゴンフォームライドウォッチ Birudo Rabitto Doragon Fōmu Raidowotchi): Based on Kamen Rider Build , this Ridewatch provides access to the BuildRabbitDragonArmor. It is dated 2017.

Behind the Scenes


Takumi Katsuragi is portrayed by Yukiaki Kiyama (木山 廉彬 Kiyama Yukiaki). In Kamen Rider Ex-Aid media and Kamen Rider Zi-O, he was portrayed and voiced by Atsuhiro Inukai (犬飼 貴丈 Inukai Atsuhiro) who plays his current identity Sento Kiryu as so to hide his alternate identity away from viewers. 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 an anti-heroic character, 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.
  • Despite being a user of Build, Katsuragi (portrayed by Yukiaki Kiyama) hasn't ever been seen transforming into Build on-screen, although he attempted in a flashback in Episode 34 until finding out Evolto switched his Driver.



Sento Kiryu (Takumi Katsuragi) - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi - Kengo Ino - Killbus - Keiji Uraga
Transformation Gear
Fullbottles - Build Driver - Transteam Gun - (Great) Cross-Z Dragon - Sclashjellies - Sclash Driver - Hazard Trigger - Nebulasteam Gun - Cross-Z Magma Knuckle - Evol-Driver - Evol-Trigger - Grease Blizzard Knuckle - Killbuspider - Grease Perfect Kingdom
Drill Crusher - Hawk Gatlinger - 4Koma Ninpoutou - Kaizoku Hassyar - Fullbottle Buster - Steam Blade - Beat Closer - Twin Breaker - Muscle Glove - Solstall Wings - Giant Scratcher - Space Ride Arm - Spine Knuckle - Long Range Cleaner - Trash Converter - Gold Lio Gauntlet - Multi Deluge Gun
Pandora Box - Halfbodies - Fullbottle Holder - Build Phone
Vortex Finish - Hazard Level - Project Build - Sky Wall - Nebula Gas
nascita: Misora Isurugi - Soichi Isurugi - Sawa Takigawa - Kazumi Sawatari - Gentoku Himuro
Prime Ministers: Taizan Himuro (Touto) - Yoshiko Tajimi (Hokuto) - Masakuni Mido (Seito)
Namba Heavy Industries Ltd.: Juzaburo Namba - Nariaki Utsumi - Guardian
Hell Bro's: Fu Washio - Rai Washio
Aliens: Vernage
Downfall: Keiji Uraga - Simon Marcus
Gentoku Himuro - Evolto - Nariaki Utsumi - Takumi Katsuragi - Shingo Kuwata - Eita Kawai
Touto: Needle Smash - Strong Smash - Burn Smash - Flying Smash - Mirage Smash - Square Smash - Press Smash - Ice Smash - Stretch Smash
Hokuto: Castle Hard Smash - Stag Hard Smash - Owl Hard Smash
Kaiser: Kaisei Mogami (World of Ex-Aid)
Kengo Ino - Ryoka Saiga - Mitsuomi Gobara - Evolto - Killbus
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