This is a partial character sheet for Kamen Rider Build. Visit here for the main character index. Subjective trope and audience reactions should go on the YMMV page.
The most patient of the three nations, they waited to enter the fray until #22, when Hokuto's over-extension into Touto allows them to capture the entire nation in one fell swoop. They soon set their sights on conquering Touto as well, while its Kamen Riders are weakened by their battle with Hokuto's forces.
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General Tropes
- Faction Calculus: The Balanced faction, with three named characters as combatants in the war compared to Hokuto's four and Touto's two. In contrast to Hokuto's further development of Smash into Hard Smash, Seito has been given a more advanced version of the Transteam System by Namba Heavy Industries to produce the Kaisers.
- Mecha-Mook: Just like the other factions, they employ Guardians as troops. Seito's are denoted by their red faceplates.
- Out of Focus: Seito, unlike Hokuto, isn't visited during the first arc of the series, and stays out of the war between Touto and Hokuto, meaning virtually nothing is known about them right up until the moment they storm Hokuto and reveal that they have their own Kamen Rider.
- Paper Tiger: It quickly becomes clear that while Touto was developing what would become the Build Driver and Sclash Driver, and Hokuto was developing what would become the Hard Smash, Seito was doing nothing to adequately prepare for war with superpowered individuals. All of their weapons instead come directly from Namba Heavy Industries, and their prime minister is Juzaburo Namba's puppet to such a degree that he's visibly cowed in Juzaburo's presence.
Prime Minister Masakuni Mido
Masakuni Mido
Portrayed by: Norimasa Fuke
- Dying as Yourself: Played With. He never recovers from the Hate Plague of Pandora's Box like the other Prime Ministers, but he holds onto his honor and promises. Its those remaining standards that ultimately get him killed.
- The Dragon: To Juzaburo Namba, as it's clear that the weapons mogul is the one pulling the strings behind Seito's military.
- Evil Is Hammy: While he's not as open about it as Tajimi, Mido quickly starts Milking the Giant Cow whenever he's near the Pandora Box.
- Hate Plague: Similarly to Gentoku and Tajimi, the Sky Wall incident has influenced him to the point where gaining control of the Pandora Box, and with it rulership of all of Japan, has become his main focus.
- I Gave My Word: Even though he was frustrated by it, he was willing to abide by the terms he agreed to after he loses the representative battle, despite Namba's recommendation that he just ignore it and continue to wage war. It's because of this that Namba decided to have Stalk kill him.
- Kill and Replace: Blood Stalk kills him and then gives Namba his face.
- Orcus on His Throne: It takes nearly half the series for Mido to make his move, but when he does it's to conquer all of Hokuto in the span of thirty seconds.
- Puppet King: He has no actual control over his own country, instead letting it become a Namba puppet state just so he can have Pandora's Box. Then Namba decides to take his place as country leader.
- Smug Snake: The only time he really shows any panic is during the the proxy fight between Seito and Touto. Most of the time he's got a smug smile on his face and a seemingly unflappable demeanor.
- He really sells it during the Touto vs Hokuto proxy fight, giving Build a slow clap with a satisfied smile on his face, before promptly annexing Hokuto.
- The Strategist: He waited for Touto and Hokuto to exhaust each other before conquering Hokuto and declaring war on Touto.
Kamen Rider Rogue
Kamen Rider Rogue
Seito’s Kamen Rider, a result of their alliance with Blood Stalk, who gave them a Sclash Driver and the means to make the Crocodile Crack Fullbottle.See his page in Kamen Rider Build Protagonists
Fu Washio/Remocon Bros/Hell Bros
Fu Washio
Portrayed by: Osamu Adachi (live), Kotaro Kaji (suit)
Young Fu Portrayed by: Shinta Takaiwa
Funky! Remote control gear!
Fever! Perfect!
- Blue Oni: He's the calmer yet more sadistic of the Washio brothers.
- Child Soldiers: He's one of the Namba Children, and so was raised from a very young age to serve Namba's purposes. In his case, he's a living weapon.
- Clipped-Wing Angel: His and Rai's true deadliness lies in their superb teamwork, which allows them to overcome their opponents (even stronger ones) by ganging up on them or neutralising their counterattacks by covering each other's blindspots. Hell Bros puts all their power into one fighter who can be outflanked, outnumbered, and overpowered by its enemies. It's also this compared to Bikaiser, as while its stats are very slightly higher, Bikaiser was created to harness the power of a world merger and takes Build RabbitTank Sparkling and Ex-Aid Hyper Muteki to defeat in a weakened state while Hell Bros lose to things nowhere near comparable to Hyper Muteki alone.
- Empowered Badass Normal: The Washio brothers were already the strongest of the Namba Children before they were upgraded to become the Kaisers. With his upgrades, Fu becomes capable of fighting on par with Sclash Riders.
- Even Evil Has Loved Ones: He genuinely seems to care for his brother, hitting Ryuga with a guilt trip by telling him that he has to win their fight or Rai will be executed. He was lying straight to Ryuga's face, as Rai shows up perfectly fine to congratulate his brother on his win and on his ruse.
- His reaction to Rai's death in #38 shows that he really did care, even if he wasn't above lying about it to get an advantage in battle.
- Freudian Excuse: He and his brother underwent Training from Hell and were brainwashed by Juzaburo Namba from childhood to know nothing but absolute loyalty to him.
- Fusion Dance: Downplayed. He and Rai do not actually merge together, but one can use both Gears to combine the forms into Hell Bros.
- Good Feels Good: His last words show that in the end he learned this.
- Fu: Fighting for someone's sake... It wasn't bad. I should tell... my brother...
- Heroic Sacrifice: Surprisingly, he actually saves Ryuga from being killed by Evolt by pushing him out of the way and taking the attack. The end result was Fu dying in Ryuga's arms.
- Jerkass: He's a vicious sadist with not many redeeming qualities, taking hostages and kicking his opponents when they're down. Though, as mentioned above in Even Evil Has Loved Ones (albeit a downplayed example), Good Feels Good and Heroic Sacrifice, he's not completely played straight as one (as his aforementioned Freudian Excuse makes clear), but not by much.
- Karmic Death: He won his representative battle against Ryuga by telling him that Rai would be killed if he loses. Much later, he ends up watching Evolt brutally kill Rai right in front of him, and then for extra irony, he himself ends up dying Taking the Bullet for none other than Ryuga.
- Killed Off for Real: Took the brunt of an attack by Evolt, killing him.
- Knight of Cerebus: Unlike the Hokuto invaders, who were dangerous but had both sympathetic and comedic moments, the Washio brothers are deadly serious.
- Power Up Letdown: Downplayed. During the beginning of its debut fight, Hell Bros was clearly holding a heavy advantage over Cross-Z Charge. However, because Ryuga spent the last week training and of his natural ability to rapidly increase his Hazard Level, the power advantage was quickly lost and reversed, forcing Fu to take advantage of Ryuga’s compassion to win.
- Taking the Bullet: See Heroic Sacrifice.
- Too Awesome to Use: Nothing stops the Kaisers from using Hell Bros all the time other than Juzaburo telling them not to: it's sufficiently better than all of his other products that he would make less money if his clients knew it existed. The representative duel with Touto's second round is finally a dire enough circumstance for him to approve its usage. It has the additional disadvantage of requiring both Gears to operate, meaning that only one of the brothers can utilize any of their powers at a time if Hell Bros needs to be called out.
- Training from Hell: Underwent brutal and desensitizing training ever since they were children.
Rai Washio/Engine Bros
Rai Washio
Portrayed by: Yuudai Nasuda (live), Keisuke Azuma (suit, episodes 23-32), Daichi Nobe (suit, episodes 37-38)
Young Rai Portrayed by: Taiga Watanabe
Funky! Engine running gear!
- Child Soldiers: He's one of the Namba Children, and so was raised from a very young age to serve Namba's purposes. In his case, he's a living weapon.
- Deader than Dead: Unlike his brother, who died much like the Three Crows, Rai was caught in a Black Hole and absolutely obliterated.
- Empowered Badass Normal: The Washio brothers were already the strongest of the Namba Children before they were upgraded to become the Kaisers. With his upgrades, Rai becomes capable of fighting on par with Sclash Riders.
- Evil Cannot Comprehend Good: He believes Kazumi is no match for him as Kazumi has never fought alone, but Kazumi's Power of Friendship instead allows him to finally defeat Rai in a No-Holds-Barred Beatdown.
- Flat Character: He's a bit of a one-note villain whose whole character can be summed up as: "Evil, and also throws Fu the Gear Engine sometimes". Unlike his brother, who at least gets some development at the end of his life, Rai remains the same brainwashed Child Soldier right to the bitter end.
- Freudian Excuse: He and his brother underwent Training from Hell and were brainwashed by Juzaburo Namba from childhood to know nothing but absolute loyalty to him.
- Fusion Dance: Downplayed. He and Fu do not actually merge together, but one can use both Gears to combine the forms into Hell Bros.
- Jerkass: When delivering his ultimatum of "Become Seito's weapon or Kiba dies", he takes a moment to viciously stomp on Kiba hard enough to elicit a scream just because he could. And judging from Kiba's continued pained struggling, he's still applying pressure even as the feed cuts out.
- Killed Off for Real:Killed off by Evolt in #38.
- Knight of Cerebus: Unlike the Hokuto invaders, who were dangerous but had both sympathetic and comedic moments, the Washio brothers are deadly serious.
- Logical Weakness: Being based off of an Engine, his Kaiser form can be weakened by being water logged or freezing. Sento takes advantage of this flaw by using Trial Forms that let him apply both.
- Red Oni: He's the louder and more ruthless of the Washio brothers.
- Training from Hell: Underwent brutal and desensitizing training ever since they were children.
