Gentoku Himuro

Gentoku Himuro (氷室 幻徳) is one of the main villains in Kamen Rider Build. The head of the Touto Institute of Advanced Matter Physics, he also took over the role of Prime Minister of Touto from his then-hospitalized father, a position overshadowed by his superior, Jusaburo Nanba. . Gentoku is also the leader of Faust, and the true idenity of Night Rogue. He is a mysterious masked figure that is present during Faust's experiments that turn victims into Smash, including the one from Sento Kiryu's memories.

Early Life
Gentoku was in the audience of the return ceremony when the Skywall was raised. Within a decade of the disaster, he became an aide to the Prime Minister of Touto, overseeing research of Pandora Box. Approximately seven years after the Skywall Disaster, Gentoku founded Faust with Takumi Katsuragi, a prodigious researcher, and Soichi Isurugi, the astronaut responsible for the disaster. Gentoku was given the Transteam System, a device designed by Katsuragi, to turn into Night Rogue. He later watches over the human experimentation it conducts and appears in Sento Kiryu's mostly forgotten memories from before his escape, sitting atop a throne. According to Gentoku himself, the reason behind these experiments is to accomplish one of Faust's objectives: to create the "Ultimate Lifeform."

Prelude to Build & Ryuga's escape
In the present day, Gentoku and his assistant Nariaki Utsumi were being interviewed by journalist Sawa Takigawa. In the interview, he recalls the Skywall Tragedy, and stated the Institute's objective is to deciphering the Pandora Box before foreign countries attempt to seize any of the current three regions. He then spots Sento approaching the vault containing the Pandora Box. Nariaki told Gentoku about Sento being a research applicant and his high test results, which impressed Gentoku. Sawa regains his attention by aksing about muplitple incident reports of people being attacked by creatures called Smash and the mysterious hero called Kamen Rider. He attempts to seduce her, which she didn't notice until he was leading her towards the lobby exit.

The next day, Gentoku accepts Sento into the Institute, with the task of analyzing the Pandora Box, which he believes is capable of producing energy that dwarfs nuclear energy itself. He then asks Sento about his knowledge of the Skywall tragedy, who then stated it was caused by the Pandora Box when it emitted a bright light, and Gentoku stated that same light also exposed people, changing their behaviors which lead into Japan divided into three countries. He was directed to the news where he and Sento learned of the criminal Ryuga Banjou escaped from prison. Gentoku told Sento he was responsible for the murder of one of Institute's researchers, Takumi Katsuragi. He was amazed as how Ryuga was able to escape a group of Guardian robots.

After Sento's battle with the Strong Smash, Gentoku, with Utsumi and several Touto military forces with Guardians, arrived and demand Sento, as Build, to turn Ryuga over to them. As the forces advance of Ryuga, Sento activates his Machine Builder and escapes with Ryuga, which forces Gentoku to capture them dead or alive. Utsumi attempts to reason with him, but Gentoku silences him and deem them unnecessary for the current stage of their plan. During the chase, Gentoku turns into Night Rogue and spies on Sento and Ryuga driving by the Skywall, stating the war has begun.

The Burn Smash incident
In order to flush out Ryuga, Night Rogue took his fiance Kasumi Ogura and brought her to Faust's lair, planning to turn her into a Smash. He found her phone ringing, with Ryuga on the other line, and answered it, letting Ryuga listen in horror as Faust scientists prepped Kasumi for the Nebula gas injection. He heads back to his chair and tells an infuriated Ryuga he will let him meet her once the infusion is complete and hangs up.

Back at the Institute, Gentoku and few researchers watch the news as the government declared Sento's alter ego Kamen Rider Build as a wanted man and displayed footage of Build attacking Guardians, which was a trap set by Faust. He told Sento the dangers of becoming a fugitive by opposing the government. After Sento left, Gentoku heads out and turns to Night Rogue, letting Kasumi, now the Burn Smash, loose back at her apartment complex. As Ryuga reaches the building, Kasumi attacks, and Rogue, in a mist form as a spectator, told Ryuga he kept his word, reintroducing his fiance, now a Smash, to her love. He watches as Kasumi attacks Ryuga until Sento appears and prepares to fight until Ryuga told him the Smash is his fiance. Solidifying himself, Rogue introduces himself to Sento, who turns into his HarinezumiTank Form while enraged and attacks, but Rogue has the upper hand as he told Sento he can't win with a random FullBottle.

As the Burn Smash attacks, Ryuga pleads with Sento to not attack her, but Sento assures him she will return to normal once the Smash element's been extracted from her body. Rejoining the battle, Rogue unveiled a horrifying truth: Kasumi's body was too weak to support the element, and removing it will cause to body to disintegrate. While Sento continues to attack and Ryuga shields Kasumi, Rogue noticed how Kasumi attacked herself rather than attack Ryuga from behind, realizing her conscious hasn't fully disappear. Sensing this, he watches as Sento turns into RabbitSoujiki to force her to use up all her fire power and turn into Gorillamond to use its Vortex Finish to separate Kasumi from the Burn Smash long enough for Ryuga to say goodbye before she disintegrated. He then leaves, having seen enough.

Blood Stalk Reemerges
At the Touto Government capital, Gentoku watched his father, Taizan, also the Prime Minister, in his monthly meeting with Hokuto's Prime Minister Yoshiko Tajimi and Seito's Masakuni Mido. Taizan asks how both countries are since the Skywall tragedy: Yoshiko presents progress for Hokuto's growht in parental support and agricultural resources, and Masakuni stats his country is sending out their young in order to restore their fragile economy, which lead Taizan to believe both Prime Ministers have no interest in reuniting with Touto to make Japan whole again. Masakuni told him it would be difficult as the Skywall cut off their resources and Yoshiko stated it will remain so until they find a way to deal with the wall. Taizan agrees and concludes the meeting. Gentoku doesn't believe them, as he told his father Hokuto's militia is increasing to match Touto's and proposes expanding their militia, but his father disagrees, stating what they have now is only for self-defense. Referring him as "father" also angers Taizan and repeats himself to refer to him as Prime Minister; he then demands to know the progress on locating Kamen Rider Build, which Gentoku told him they were unsuccessful. Taizan tells Gentoku to find the Kamen rider quickly, and in doing so would soothe the fear that'sbeen cast over Touto.

At the Institute, Sento asks Gentoku and Utsumi about a man named Masahiro Nabeshima and him being possibly connected to Katsumi's murder, to which Gentoku lied about not knowing him. Sento then switches topic and asked what kind of person Katsumi was, and Gentoku told him Katsumi was a genius and in charge of the research on the Pandora Box. He also told Sento Katsumi was called the "Demon Scientist". After Sento left, Gentoku turned into Night Rogue and approached Nabeshima, telling him he has his wife and daughter hostage in Seito. In cooperation, he forced Nabeshima to answer his cell phone, with Ryuga on the other line and to tell him about his involvement with the organization Faust and his family being hostage in the sixth District of Seito. After hanging up, he pleads with Rogue to release his family, but Rogue drags him back to Faust's lair and have him prepared for the Nebula gas infusion, praising Nabeshima's work as a covert operative before he became the Mirage Smash. Later that night, Gentoku sits in a car while examining the Rocket Fullbottle, sensing that Blood Stalk has finally made his move.

Brought back by Stalk, Gentoku had the Faust scientists administer the Nebula gas into Nabeshima again, but he broke free and turns into an incomplete Square Smash. Gentoku theorizes a second dose of the Smash element increases the subject's destructive power before the incomplete Smash attacked him. However, Gentoku overpowers it and and brings it down with his Transteam gun while adhering himself to the lair's roof and jumping down to deliver a finishing punch. He told the Smash that Faust's main objective was to create the ultimate life form and ponders the possibility of administering another dosage to an already experimented Smash.

The next day at the Institute, Sento presents a recording of the Skywall tragedy to Gentoku and Utsumi. Utsumi demands to know where Sento retrieved the footage, but Gentoku assures him it's fine before vacating the main hall to leave him, Utsumi and Sento alone. Sento shows a modified footage by removing the light cast after the astronaut responsible for the Skywall tragedy, revealing that the Pandora Box had six, colored matching panels, two red, two blue and two green, that gave it a dual structure before they were separated. Sento surmises that the two green panels should be somewhere in Touto, but Gentoku told him there are no panels. Sento demands there are two green panels before Gentoku becomes enraged and ceases talking to him, but Sento surmises the possibility of the panels being stolen by an underground organization named Faust.

Ustumi seizes Sento, but Gentoku stays his hand and asks Sento where he heard the name Faust, then concedes to the panels actually exist but were stolen three years ago, and that by concealing the truth would prevent mass hysteria to the public and that both Seito and Hokuto are after the Pandora Box for their own nefarious purposes. Sento asks how Faust got past Touto's security and Gentouk mentions the possibility of a traitor and shows Sento the astronaut running towards the box. Returning to the lair, Gentoku places the Rocket FullBottle in one of the green panels attatched to a frame beside his chair, asking Stalk as he returned why he didn't kill Sento. Stalk assures him his strategy-making habit always appear beneficial and that their plan is going according, even by sparing Sento.

Having himself been exposed as Blood Stalk, Soichi Isurugi revealed to Sento that the true Night Rogue was Gentoku Himuro.

Personality
"One of our objectives is to create the ultimate life form. I wonder what would happen if someone who was injected with the Smash element underwent experimentation again. I'll have to run a test."

- Night Rogue shows his malicious nature

Gentoku is a composed and generally calm man, rarely changing his tone of voice unless agitated. Underneath his cool exterior, he is a man with questionable morals at best: he flirted with a journalist, and referred to Ryuga and Kamen Rider Build as toys, as well as his fiery temper whenever he commands his soldiers. During a conversation with Gentoku, Blood Stalk reveals that Gentoku's goal is to mass produce Kamen Rider technology from his experiments for military use. To what reason or purpose is unclear, but Gentoku seems determined to see this project succeed and will do everything he can to silence or stop anyone who will interfere with this plan. He also didn't hesitate to kill his decoy with his own hand to get press in his favor.

It is likely that some of his negative personality traits are a result of his exposure to Pandora Box during the Skywall disaster. One of those traits seems to be episodes of paranoia and aggression, urging his father that they need a military to crush Seito and Hokuto before they crush Touto, believing they are out to get the capital and superior military might can stop their advance.

However, as Night Rogue, he is very malicious. Seeing innocent people as mere guinea pigs, he doesn't hesitate to experiment on them, even when fully knowing that his subjects would be too weak to survive. Despite his cold and calculating personality, Gentoku has his own standards and shows little to no tolerance with insubordination. He is easily vexed each time Soichi goes against his orders, which drives a wedge between their collaboration. He is also appalled when Soichi, as Blood Stalk put his father to the hospital for the second time before Taizan was about to resume his duty as Prime Minister.

Powers and Abilities

 * Hazard Level 3+: According to Gentoku as Rogue, his Hazard Level is above 3 (stated to be much higher than Cross-Z's), thus making him capable of fighting on par with the Kamen Riders.
 * Hand-to-Hand Combat: Though briefly, he was seen to easily block and counter Ryuga Banjou's punches, who himself was a professional fighter.

Forms
"Bat! Mistmatch! Bat...Ba-Bat... Fire!"

- Transformation announcement

Ability Perimeters: Like Blood Stalk, Night Rogue's form is accessed with the Transteam Gun and the Bat Fullbottle.
 * Height: 197.5 cm.
 * Weight: 103.0 kg.
 * Punching power: 17.2 t.
 * Kicking power: 20.5 t.
 * Maximum jump height: 49.0 m.
 * Maximum running speed: 100 m. per 4.1 sec.

Night Rogue seems to possess a degree of steam manipulation as he can turn himself into steam to quickly travel long distances or to summon his Steam Blade. Night Rogue is also shown to be able to fly as well as walk on ceilings. He can also execute an electrified Rider Punch-esque attack where his fist glows blue with electric energy and hits the target.

Night Rogue can summon a pair of wings on his back that allows him to fly and attack from the sky.

Unlike Build, Night Rogue's Ability Perimeters are not spread out between his arms and legs. While Night Rogue gets power from only one Fullbottle, he is much stronger than Build's Trial Forms, and his stats even surpass some of Build's Best Matches.

With the Steam Blade or the Steam Rifle, he can use the following attacks:
 * Elek Steam (エレキスチーム): Night Rogue shoots electricity at the enemy.
 * Ice Steam (アイススチーム): Night Rogue performs a series of icy slashes at the enemy causing them to freeze.
 * Devil Steam (デビルスチーム): Night Rogue fires a "steam" bullet which will home in on the target and inject them with an unknown compound when it hits them. When used on a human, the person will turn into a Smash. When used on a Smash, the Smash will grow to gigantic proportions.

Night Rogue has 4 finishers:
 * Transtream Gun finishers:
 * Steam Break (スチームブレイク): Night Rogue channels the powers of a Faust Fullbottle and performs a powerful blast attack.
 * Bat:
 * Steam Attack (スチームアタック): Night Rogue channels the powers of a normal Fullbottle and performs a powerful blast attack.
 * Steam Rifle finishers:
 * Steam Shot (スチームショット): Night Rogue channels the powers of a Faust Fullbottle and performs a powerful steam blast attack.
 * Bat:
 * Steam Attack (スチームアタック): Night Rogue channels the powers of a normal Fullbottle and performs a powerful steam blast attack.

Appearances: Build Episodes 1-7, Transformation Lessons: Night Rogue Chapter, Build 8-13, 15-16, 20

Devices

 * Transteam Gun - Transformation device and personal weapon.
 * Fullbottles - Transformation trinkets.

Weapons

 * Steam Blade - Standard sidearm weapon. Can combine with the Transteam Gun to form the Steam Rifle.

Portrayal
Gentoku is portrayed by Kensei Mikami (水上 剣星). As Night Rogue, his suit actor is Jun Watanabe (渡辺淳), who played Secondary Riders since Kamen Rider Drive.

Etymology
Night Rogue's name is formed from the English words “Night” and “Rogue.” The name as a whole seems to be a pun of the word “Nitro”, possibly referencing Night Rogue’s Steam Engine Motif.