He was originally Night Rogue, the leader of the enigmatic organization Faust and the main antagonist of the "Birth" arc. However, after becoming Kamen Rider Rogue, Gentoku defects to the heroes' side to stop Namba Heavy Industries from conquering Japan and later to defeat Evolto before he destroys the world.
He also appears as the protagonist of the three-part ROGUE Blu-Ray miniseries which details his origins as Night Rogue.
Within a decade of the raising of the Skywall, Gentoku rose to a prominent position within the Touto government, being the one in charge of conducting research of the Pandora Box.
Seven years after the Skywall's emergence, Gentoku founded Faust along with researcher Takumi Katsuragi and Soichi Isurugi, the astronaut who had caused the Skywall Disaster. Katsuragi designed the Trans team System for Gentoku to use to transform into Night Rogue.
Pursuit of Ryuga
Gentoku is first seen being interviewed along with his assistant, Nariaki Utsumi by Sawa Takigawa, where he states that the Institute's objective is to decipher the Pandora Box before other countries attempt to invade any of the three regions of Japan. The following day, Gentoku accepts Sento Kiryu into the Institute to assist in studying the Pandora Box. The two soon hear of the news that Ryuga Banjou has escaped from prison. Gentoku tells Sento that Ryuga murdered one of the Institute's researchers, Takumi Katsuragi.
Following Sento's battle with Strong Smash, Gentoku and an army of Touto Guardians and soldiers arrive and demand Build hand over Ryuga. However, Build chooses to instead escape with Ryuga, prompting the Touto forces to go after them.
Night Rogue later kidnapped Ryuga's fiance, Kasumi Ogura, to be turned into a Smash. When Ryuga called her, Night Rogue answered her phone and forced Ryuga to listen as Kasumi was prepared to be injected with Nebula Gas. Following Kasumi's conversion into the Burn Smash, Night Rogue unleashes the monster and sends it to attack Ryuga. With it being too late to save Kasumi due to her being a "Hazard Level 1", Build was forced to kill her to end her suffering.
Gentoku as Prime Minister
With his father falling ill, Gentoku assumed the position of acting Prime Minister of Touto. He met with Yoshiko Tajimi, the Prime Minister of Hokuto and Masakuni Mido, the Prime Minister of Seito. At the meeting, Tajimi accused him of collaborating with Faust, but Gentoku replied by suggesting she has relations with Faust.
He was later approached by Blood Stalk, who demanded to know why Gentoku had placed the Pandora Box in an unknown location and not informed Stalk, but Gentoku told Stalk to act more loyal if he wanted Gentoku to reveal the Box's location. Their conversation was interrupted by two Touto security guards, whom Stalk killed effortlessly.
Night Rogue later skirmished with Sento and Ryuga as they entered the Namba Heavy Industries Integrated Science Laboratory to find the Pandora Box. During the fight, Stalk interferes and attacks Night Rogue before locating the Pandora Box and teleporting away from it.
While Utsumi treats his wounds, Gentoku is approached by Faust's benefactor, Juzaburo Namba. Gentoku apologizes for letting the Box be stolen, and Namba forgives him, but states that countermeasures must be taken. The two decide to have the Touto government destroy Faust to remove any traces of evidence connecting them to it.
The following day, Gentoku stages a confrontation with Faust at a dam, with Gentoku leading the Touto forces while his assistant poses as Night Rogue. The impostor Night Rogue fights and is quickly defeated by Build KaizokuRessya. The defeat is picked up by the news, with Utsumi being forced out of his transformation and incriminated as the leader of Faust. Utsumi attempts to inform Build of something, but before he can finish speaking Gentoku shoots him and knocks him off the bridge and into the waters below.
Meeting with Namba again, Gentoku is informed that Namba has found a new partner. He later contacts Blood Stalk and arranges a meeting with him. At the meeting, Gentoku attempts to get Blood Stalk to give up the Box's location. Blood Stalk agrees, but only if Gentoku swears loyalty to him. Gentoku refuses and transforms into Night Rogue to fight Blood Stalk and take the Box by force. Initially beating back Stalk, Night Rogue soon realizes that Stalk was holding back and is swiftly defeated by him. Stalk then reveals that he is Namba's new partner.
Gentoku later reveals to Sento and Ryuga that the Box is in one of Namba Heavy Industries' storage facilities, planning to have the two retrieve the box for him. However, after being exposed as Soichi Isurugi, Blood Stalk reveals that the true identity of Night Rogue is Gentoku Himuro.
After Sento and Ryuga succeed in recovering the Box, Gentoku sends a squad of Touto soldiers to break into nascita but they find no traces of the box. Gentoku later meets with Sento and Ryuga in the Touto Institute's parking lot, who reveal that they know Gentoku is Night Rogue and show him the box. After Gentoku reveals his plans to the Riders, Ryuga loses his temper and attacks Gentoku, who transforms into Night Rogue to fight him. Night Rogue manages to overpower both of them and recover the Box, only for it to be revealed to be a hologram, with the whole confrontation being a ruse to expose Night Rogue's true identity.
Meeting with the other two Prime Ministers again, Gentoku states that Touto has recovered the Pandora Box. As Masakuni Mido congratulates him, Gentoku tells the two to drop the facade and that all three of them want the energy of the Pandora Box for their own selfish desires. Tajimi at first pretends not to know what Gentoku is talking about, but Gentoku then proceeds to point out how most of Hokuto's budget is spent on its military, angering Tajimi. Gentoku then proposes that the three should see which one could rule Japan, before Tajimi and Mido cut off their transmissions.
The next day, Gentoku is informed that a squad of Hokuto Guardians and two Smash Hazards have crossed the border into Tokyo. Declaring it an act of war, Gentoku informs Sento and Ryuga that this is an invasion. He later sends Touto Special Forces to bring Sento and Ryuga to them, offering to overturn Ryuga's prison sentence if the two fight for Hokuto. While Sento was initially reluctant, Ryuga agreed, and Gentoku provided the two with bracelets that would allow him to monitor their location and contact them at all times.
Defection to Seito
Gentoku's identity as Night Rogue and connections to Faust were later exposed to Taizan Himuro and the Touto government after his father was healed by Misora. Gentoku transformed into Night Rogue and made an attempt to steal that Pandora Box, but was easily fought off by Build.
After being banished from Touto, Gentoku traveled over to Seito to defect tot hem. Heading to the Namba Heavy Industries Seito office, Gentoku approached Nariaki Utsumi and demanded to be made into a Kamen Rider, but Utsumi demanded he kneel first. Begrudgingly, Gentoku complied and kneeled, only for Utsumi to tell him he never promised to make him into a Kamen Rider and leave him chained up in a cell in a Faust compound run by Namba Industries.
However, Gentoku was later approached by Blood Stalk, who offered to train him to raise his Hazard Level so he could become a Kamen Rider. While they already had a candidate to become the Kamen Rider of Seito, Stalk noted to Utsumi that he lacked the drive to obtain more power that Gentoku had. Gentoku was thus transferred to a cell with four other inmates. While one of the inmates was kind, the other three were hostile to him and frequently beat him. In one struggle with the three inmates, Gentoku was brutally beaten to the point of losing consciousness, causing him to be proclaimed as dead and taken to a morgue. However, while he was there he was rescued by two of his old comrades in Faust, Norio Matsui and Yoshikazu Takahashi. Upon waking up, Gentoku hugged both of them and told them he was eternally indebted to them. Gentoku later returned to the Faust compound and murdered the lead candidate for Kamen Rider so he could take his Sclash Driver. He was soon discovered by Stalk and Utsumi and asked the two what they intended to do now that their candidate was no longer qualified to be Seito's Kamen Rider. Impressed with Gentoku's cold-blooded murder, Stalk informed him that he was now in line to become Seito's Kamen Rider.
In order to raise his Hazard Level to the point where he could use the Sclash Driver to transform into Kamen Rider, Stalk had Guardians attack Gentoku all at once, beating him over and over again until he his Hazard Level was finally raised to the point where he could utilize the Sclash Driver. Inserting the Crocodile Fullbottle into his Sclash Driver, Gentoku achieved becoming a Kamen Rider and proclaimed himself as "Kamen Rider Rogue".
With his new power, Gentoku became the Kamen Rider of Seito and the commander of Seito's forces, spearheading their invasion into Touto. He made an attempt to seize the Pandora Box as Taizan was having it moved to a new location.
Eventually, a three-on-three representative match was agreed upon by the nations in which Seito's three champions would fight the three champions of Touto for possession of the Pandora Box and Fullbottles. Rogue thus fought Build in the third round of representative battle, following one victory for Touto and one victory for Seito. Mocking Sento for his insistence that science was only a tool for war, Gentoku rejected Sento's claims that science could be used for peace, asking him why he had designed the Hazard Trigger as Katsuragi if not for war. While Sento was pondering what Gentoku had said, Rogue used the opportunity to get an attack in on him. Despite he initially having the advantage, the tables soon turned against Rogue when Build revealed his RabbitRabbit form and promptly beat Rogue down. However, Namba Heavy Industries had received the data on Build's RabbitRabbit form from Sawa Takigawa, whom they had blackmailed into working for them again by holding the Nabeshima family hostage. Nariaki Utsumi thus downloaded the data into Rogue's systems, allowing him to gain the edge out over Build once again. Unbeknownst to Rogue and Namba Industries, Sawa had secretly told Sento about her ties with Namba Industries and what they had done with the Nabeshimas. The two thus plotted to outsmart the company by only leaking half of Sento's research data. After Grease rescued the Nabeshimas from Seito's Guardians, Sawa received the go-ahead from Grease and passed it on to Sento, who changed from his RabbitRabbit form to his TankTank form, which Namba had no data on. Unprepared to deal with Build's new form, Rogue was beaten down and defeated by him, clamining the third round for Touto and allowing them to win the representative match.
Despite losing, Namba refused to allow the Pandora Box to be handed over, and killed and swapped faces with Seito's Prime Minister Masakuni Mido when he attempted to honor the deal. However, Gentoku disagreed with how Namba intended to use the Pandora Box to take over the world and overheard Namba reveal he had assumed the identity of Mido. During a fight with Build, Rogue revealed that Namba was impersonating Mido and that he had a chip implanted in him set to go off should he disobey or go against Namba.
Rogue was later tasked with guarding the captured workers of Kazumi Sawatari's farm when Seito attempted to use them to extort Kazumi into trading them the Pandora Box in exchange for freeing them, lest they be executed. Kazumi refused and, rather than carry out his orders and execute them, Rogue instead let them go.
Capturing Taizan to prove his loyalty to Namba, Gentoku later set his his father free and attempted to escape. However, he was confronted by Utsumi. Stalk then activated Gentoku's kill switch, immobilizing the Rider and foiling his escape attempt.
However, Gentoku's kill switch had been deactivated by Sento beforehand, allowing him to go on to fight alongside Sento and Banjou as Rogue. Rogue later assisted Build, Cross-Z and Grease in fighting against Stalk. After Stalk was defeated by Cross-Z Magma, he attempted to escape but was pursued by Rogue. Rogue then defeated Stalk again and canceled Evolt's transformation.
However, thanks to Utsumi, Evolt gained the Evol Driver and used the Cobra and Rider Evolbottles to transform into Kamen Rider Evol. Evol then defeated Rogue and caused Gentoku to revert his transformation. He attempted to finish Gentoku off, but his attacked was blocked by Taizan, who sacrificed himself to save his son. Before dying, Taizan asked Gentoku rebuild Japan as a whole and acknowledged Gentoku as his being his son.
Fighting alongside Build
Siding with Team Build, Gentoku vowed to atone for his sins by reuniting Japan and laying the foundation for a new generation. However, there was still some uneasiness among Build's allies, especially Kazumi, due to Gentoku having killed Akaba, though Kazumi eventually would encourage Gentoku to keep trying to make up for his past actions.
After Utsumi went insane and sided with Evolt to become Kamen Rider Mad Rogue following Namba's death, Gentoku blamed himself for Utsumi's turn over to Evolt, having been the one to shoot him at the confrontation at the dam. When Utsumi led an attack on Touto, Gentoku attempted to go and confront him, but proved too injured from his previous defeat by Utsumi as Mad Rogue to do so.
Later, as the nascita crew were discussing Evolt's actions and speculating as to what his true plans were, they realized that most of the people who had been turned into Smash were people with a connection to Shinobu Katsuragi. They asked Gentoku if he had information on that, but Gentoku denied knowing anything claiming that Smash conversions was Stalk's department in Faust and not his.
After Evolt revealed his extraterrestrial origins to the world and announced his intentions to destroy it, he challenged the Kamen Riders to a final battle to decide the fate of planet. Alongside his fellow Kamen Riders, Gentoku showed up to confront Evolt at the summit of the Pandora Tower. Evolt then explained to them the rules of their fight: they would have to reach the top of the Pandora Tower and for every ten minutes that they didn't he would destroy a section of Japan. After Evolt teleported off and sent his army of Hard Guardians after them, Gentoku and the others transformed into their Rider forms and obliterated the Hard Guardians by combining their attacks.
Making their way inside the tower, after Grease stayed behind to fight the Hokuto Three Crow mimics, Rogue, Build and Cross-Z found themselves confronted by mimics of Remocon Bro's and Engine Bro's. Telling Build and Cross-Z to go on without him, Rogue stayed behind to fight them. He soon receives backup in the form of Mad Rogue, who reveals he was only pretending to be on Evolt's side all along. The clones then merge to form Hell Bro's, but the two Riders manage to destroy it with their combined power, causing it to drop the Hammer Lost Bottle. Kamen Rider Evol then shows up to claim the Lost Bottle and fights the two Riders, knocking Gentoku out of his transformation and fatally injuring Utsumi, who is revealed to be a cyborg.
Evol then attempts to finish Gentoku and Sawa off with the Steam Blade, but Utsumi gets up to block the attack, sacrificing himself to give the two time to gather the Lost Bottle and escape by teleporting away.
At the top of the Pandora Tower, Gentoku, along with Sento, Ryuga and Sawa, learned from Misora that Kazumi had been killed. Evolt then showed up to fight the three remaining Riders. Evol easily manages to beat down Rogue before overpowering Build and stealing the two remaining. Lost Bottles he needed to become his final form. After transforming into his monster form, Evol beats down the three Riders again and knocks Sento and Ryuga out of their transformations before creating a massive black hole to begin consume the Earth.
Despite his injuries, Rogue refused to go down and attempted to fight Evolt by himself. Despite his best efforts and determination, Rogue was unable to do any damage against Evolt and was overwhelmed by the alien's power, having part of his faceplate shattered in the process. Not ready to go down just yet, Gentoku switched tactics from attempting to fight Evolt to going for the Evol Trigger, the source of Evolt's power. He succeeds in landing a powerful blow to it and damaging it, but this did not stop Evolt from critically wounding him. Reverting from his transformation, Gentoku began to fade away. As he reached the end of his life, Gentoku entrusted the future of the world Sento, whom he acknowledged as "Sento Kiryu" instead of "Takumi Katsuragi" for his first and only time before dying.
In the new world creating by merging the World of Build into the main Kamen Rider world, Gentoku was seen acting as an aid to his father Taizan Himuro, who was now the Prime Minister of all of Japan. He was shown agreeing to an interview from Sawa Takigawa.
Kamen Rider Build NEW WORLD: Kamen Rider Cross-Z
However, Gentoku had his memories of the World of Build restored along with the rest of Team Build after Killbus opened the Pandora Box again. Reuniting with his old comrades, Gentoku and the others were informed by Sento of the threat Killbus posed.
Kamen Rider Rogue and Kamen Rider Grease later showed up to rescue Ryuga from Killbus, teleporting away with him and Yui Mabuchi. When Ryuga went to go face off against Killbus, Gentoku and Kazumi accompanied him and fought off the Clone Smash Killbus summoned.
At the end of the special, after Killbus has been defeated, Gentoku reacts to Ryuga and Yui's relationship by asking via t-shirt if they are a "best match".
Kamen Rider Build NEW WORLD: Kamen Rider Grease
Gentoku served as a translator during his father's meeting with UN representative Simon Marcus to discuss the Rider System. Gentoku later led Simon into another room where Shinobu Katsuragi showed to him the Build Driver. When Downfall terrorists assaulted the meeting, Gentoku transformed into Kamen Rider Rogue to fight them off, but he had his transformation disabled by Simon Marcus, who was secretly Downfall's leader, using Phantom Crusher's powers. Gentoku was then taken hostage by Downfall.
However, Gentoku was later rescued by Sawa Takigawa, who fed him a Nebula Gas elixir that restored his ability to transform. Gentoku then joined the other Kamen Riders in fighting off the Downfall attack.
After Downfall was defeated, Gentoku met with Sento and Ryuga again. The two noted that Gentoku had shaved off his beard, to which Gentoku and Sawa revealed they were engaged, with the two both wearing matching dress t shirts.
Transformation Lessons ~The Laws Of Transformation Are Set!~
Gentoku Himuro appears in the second episode "Night Rogue Chapter" where he attempts to film a video of him transforming into Night Rogue for FausTube, but has to restart several times after his cameramen tell him he is acting too scary. Eventually, Gentoku is able to complete his transformation into Night Rogue. He then attempts to demonstrate his Steam Rifle's finisher, Steam Shot, only for it to destroy the camera, ending the video.
As Night Rogue, Gentoku displays an arrogant and cold personality, treating people as mere guinea pigs and gleefully experimenting on them. He seems to enjoy using people's loved ones against them in order to keep them under his thumb, or just to be cruel to them, as shown when he turned Ryuga's girlfriend Kasumi into a Smash and made him listen as the transformation was taking place. Gentoku was also quick to let out emotional outbursts, and is susceptible to episodes of paranoia and aggression, desperately attempting to convince his father to improve the military believing that Hokuto and Seito are out to invade Touto. This paranoid and controlling personality stemmed from his exposure from the Pandora Box.
As his regular self, Gentoku keeps a composed and cool demeanor, though he switches to a fierce one when he is commanding his soldiers. He also seems to care for his father, and was worried for him when he suffered a heart attack that left him in the hospital, though this was soon superceded by his glee at the fact that this left him as the acting Prime Minister of Touto.
Post his redemption, Gentoku generally remains silent, having become somewhat emotionless due to the training he endured to become Kamen Rider Rogue. He is also shown to feel guilty for the crimes he committed in the past as Night Rogue and the commander of Seito's forces, and displays a desire to atone and lay the foundation for a new generation. As revealed by Evolt, Gentoku's nicer personality is due to his Hazard Level being above 4 and thus nullifying that Pandora Box's effects on his personality that made him power hungry and cruel.
Eventually, Gentoku begins to display the more comedic aspects of his personality to the rest of Team Build. He is shown to have a rather odd fashion sense, preferring overly extravagant clothes that are generally odd for a casual setting, such as the Jamaican-style robes and hat he wears in episode 41. He also enjoys wearing dress shirts and sometimes communicates by wearing shirts that say what he is thinking, something that annoys Sawa. Despite the two not trusting each other at first, Gentoku develops a camaraderie with Kazumi Sawatari and the two often go into battle together.
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