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.
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Foundation X
Kaisei Mogami
Kaisei Mogami/Kaiser/Kaiser Reverse/Bikaiser
Portrayed by: Kenji Ohtsuki (live), Yuji Nakata (suit)
Kaiser
Funky! Remote Control Gear!
Kaiser Reverse
Funky! Engine Running Gear!
Fever! Perfect!
A scientist existing in two parallel worlds; the one in the main world of Rider shows is a Foundation X agent and the one in the World of Build is an associate of Faust’s founder, Takumi Katsuragi. He created the Enigma device with the intent to merge the worlds and become an omnipotent being. The Kaisei from the World of Build uses the Nebula Steam Gun and a blue Gear Remocon to become Kaiser, while his counterpart from the main universe instead uses a red Gear Engine to become Kaiser Reverse. The two can merge into the more powerful Bikaiser.
- Big Bad Duumvirate: Both his World of Build and World of Ex-Aid counterparts share the spot of the main antagonist of Heisei Generations FINAL.
- Fusion Dance: Unlike the later Hell Bros, the Kaisers physically fuse into Bikaiser.
- Gratuitous English: The one from the World of Ex-Aid has a fondness for the word “funky,” which is probably why the Nebula Steam Gun says it so much.
- Immortality Seeker: The fusion into Bikaiser is intended to make the two Mogamis into an immortal being.
- Kick the Dog: When the heroes confront the World of Ex-Aid version of Mogami in his lair, he draws special attention to the fact that one of the Greeed clones he sics on them is a copy of Ankh, and has it fight Eiji for a Fighting Your Friend battle.
- Mad Scientist: Both of them. The one from the main universe is especially bombastic and sadistic.
- Ninja Pirate Zombie Robot: They’re a cyborg and his other-dimensional counterpart who fuse using the combined powers of Nebula Gas and the Bugster Virus.
- Red Oni, Blue Oni: The pair are basically this to each other; the one from the World of Build is calm and sadistic, while the one from the main Rider universe is loud and ruthless. Appropriately, their Gears are in the appropriate colors for their respective personalities.
- Revenge: The World of Build’s Mogami harbors a grudge against Takumi Katsuragi for betraying their partnership and causing the accident that disfigured his face.
- The Starscream: While never stated in dialogue or really brought up, it can be inferred that the Mogami who works for Foundation X is betraying them just like Lem Kannagi before him; using their resources for his own Take Over the World ambitions.
Blood Tribe (unmarked spoilers)
Evolt's race and the main antagonists of TV series, Kamen Rider Build: Be The One summer movie and Kamen Rider Build New World Kamen Rider Cross Z V-Cinema. Originally from Planet Blood, its higher echelons escaped after their leader destroyed their home planet. Not much known about their early history, apart from being Obviously Always Chaotic Evil aliens who devoured countless of planets across the universe.
General
- Absolute Xenophobe: To them, all other lifeforms are pests to be done away with. This even includes fellow Blood Tribe aliens if they get in the way.
- Always Chaotic Evil: Every Blood Tribe alien we come across is a ravenous Planet Eater.
- Blob Monster: Their true forms have shades of this, as they appear made of some sort of liquid.
- Demonic Possession: All the members we see are capable of possessing others to blend in.
- Deck of Wild Cards: As one would expect from a group of Omnicidal Maniacs, loyalty isn't their strong suite. Killbus is happy to kill his own species to satiate his lust for destruction, Evolt's cohorts end up betraying him when he stalls destroying Earth and Evolt's own goals would presumably see the rest of his kind wiped out.
- Dying Race: Thanks to Killbus, the entire species has been reduced to single digits and throughout the series all but Evolt and the hybrid Banjo are killed off.
- Enemy Civil War: While they're all Omnicidal Maniac, they differ in how they want to go about it, resulting in them coming into conflict with one another. Evolt wants to draw out destroying planets for his own amusement, Blood and his faction desires to destroy Earth as quickly as possible so they can move on to the next one, and whereas the other members want to survive the destruction of everything, Killbus wants to destroy literally everything, himself and the rest of the Blood Tribe included. The latter is why Evolt and the rest of the Tribe stole Pandora Box and headed off on their own.
- Even Evil Has Standards:
- The majority of the surviving Blood Tribe just want to kill everything in a quick and orderly manner and thus object to Evolt's desire to draw out destroying Earth out of sadism and trying to enhance himself. This causes them to have a falling out with him and attempt to destroy Earth themselves.
- While they all want to destroy everything, even Evolt wants to survive destroying everything else. As a result, the other survivors objected to Killbus wanting to kill the Blood Tribe too and stole the Pandora Box and fled.
- The Man Behind the Man: Be the One shows they played a role in manipulating the Japanese Civil War into kicking off. Evolt's three cohorts all posed as advisors to the three Prime Ministers and pushed them into waging war.
- Minor Major Character: The Be the One Blood Tribe members are extremely important to the story of Build, having helped Evolt facilitate the current state of Japan and revealing more about his origins and motivation. They also only appear in Be the One and are ultimately a footnote in Evolt's plan that he doesn't even mention in-series.
- No Name Given: We don't ever learn what the names of the three other Blood Tribe members seen in Be the One are.
- Obviously Evil: The name "Blood Tribe" should be enough to let you know these aren't friendly aliens.
- Omnicidal Maniac: An entire species of them dedicated to destroying all planets they come across.
- Planet Eater: Devour planets to become stronger.
- Rank Scales with Asskicking: The "royal family" Blood Tribe aliens, Killbus and Evolt, are much stronger than the rest of their species and possess powers that the lower members don't, such as the ability to split themselves off.
- There Is Another: Be the One reveals to us Evolt had three other Blood Tribe members helping him. Then in New World we learn about Killbus.
- Walking Spoiler: They are related to what Evolt actually is and also indirectly caused the events of the series.
Kengo Ino
Kengo Ino/Kamen Rider Blood
Portrayed by: Masanobu Katsumura (live), Yasuhiko Imai (suit)
Are you ready? Overflow! Wake up Cross-Z! Get GREAT DRAGON! Buraburaburabura Bura~h! Yabei!note
The new governor of Touto following the reunification of Japan. In truth, Kengo is a member of Evolt’s species, the Blood Tribe, and arrived with two others of his kind shortly after Evolt reached Earth, working together with Evolt behind the scenes. Using the Cobra Lost Fullbottle with a Build Driver, combined with the Hazard Trigger and Great Cross-Z Dragon, Kengo can transform into Kamen Rider Blood.
- Big Bad: The main villain of the movie. He is the one behind the plot to brainwash all of Japan and his Kamen Rider form makes him a deadlier threat than either of his cohorts.
- Big Bad Wannabe: He tries to usurp Evolt over Evolt’s desire to drag out the destruction of Earth for his own purposes, but ultimately he requires a mishmash of upgrades and devices to approach artificially what Evolt has naturally. In the end he ends up on a similar level to Build Genius, at a stage when Evol Black Hole is perfectly capable of taking on all four riders at once. Doubled down in New World which introduces Killbus, Evolt’s older and stronger brother. Forget trying to keep up, Blood’s not even on the same track.
- Can't Catch Up: He’s the second strongest of the Blood Clan in the movie, but he's second to Evolt by a gigantic margin. Ino can only become Kamen Rider Blood by kitbashing parts of Build Hazard, Great Cross-Z, and Blood Stalk together with a Build Driver and has to fuse with the other members of the Blood Tribe to do it. Even after jumping through all of these hoops, he’s still only on par with Evol’s base form, and saved from a thrashing by the fact Evolt is too lazy to bother dealing with Blood himself when he can just make Sento do it for him. Even his jingle is underwhelming, as it simply adds the Hazard Trigger sounds and a weak added sound to Great Cross-Z’s jingle.Great Cross-Z Dragon! Build Up! Are you ready? Overflow! Wake up Cross-Z! Get Great Dragon! Buraburaburabura Bura~h! Yabei!
- In the grand scheme of things, he's the third most powerful of the Blood Tribe overall. Everything that applies to him as detailed above is magnified by an enormous factor when Killbus is taken into account.
- Hypocrite: The Blood Tribe aren’t the paragons of moral honor, but Ino stands out among them, chastising the Kamen Riders for being tools of war, never mind half of what the Blood Tribe has pulled and destroyed. And that Ino happily brainwashed an entire nation to Mind Rape Sento.
- No Name Given: 'Kengo Ino' is the name of the human who he possessed and replaced. Unlike Evolt and Killbus, his real name is never actually revealed.
- Offstage Villainy: Ino and the other members of the Blood Tribe were working behind the scenes the whole time to help Evolt orchestrate his schemes by manipulating the three factions while he was busy setting up Faust. His gift of Japan’s three nations to them was intended as the reward for their help, not that they’re grateful when they’d rather just blow the planet up and move on.
- Omnicidal Maniac: Like Evolt, given they’re the same species. However, Blood just wants to destroy Earth and be done with it, causing a falling out between him and Evolt.
- Pragmatic Villainy: While he does want to destroy the Earth like Evolt, he has no interest in drawing things out for fun like Evolt and just wants Earth destroyed. This results in Blood and his fellows falling out with Evolt.
- The Starscream: Played With: he was originally subservient to Evolt along with the other two governors, and Evolt is naturally far stronger than them. However, it’s Evolt who deviates from the plan for his own ends, Blood is merely trying to carry out the original plan.
- This Cannot Be!: Exclaims this when Cross-ZBuild lands his Rider Kick on him.
Ryoka Saiga
Ryoka Saiga/Scissors Lost Smash II
Portrayed by: Rena Matsui (live), Yasuaki Ishii (suit)
- Blade Below the Shoulder: She is loaded with bladed weapons on her arms as the Scissors Lost Smash.
- Co-Dragons: One of Kamen Rider Blood's two main helpers, along with Gobara.
- Dark Action Girl: Can transform into the Scissors Lost Smash to do battle.
- Leg Focus: The camera takes time showing off the actress's legs.
- No Name Given: 'Ryoka Saiga' is the name of the human who she possessed and replaced. Unlike Evolt and Killbus, her real name is never actually revealed.
- The Smurfette Principle: She is the sole female of Be The One's main villains, and the only female member of the Blood Tribe overall, or at least the only one using a female host.
- This Cannot Be!: Spends her last moments in disbelief that a human could kill her since the Blood Tribe is "supposed to be stronger."
Mitsuomi Gobara
Mitsuomi Gobara/Zebra Lost Smash II
Portrayed by: Takeshi Fuji (live), Hajime Kanzaki (suit)
- The Brute: His Zebra Lost Smash form puts physical force first and foremost.
- Co-Dragons: One of Kamen Rider Blood's two main helpers, along with Saiga.
- Family-Unfriendly Death: Gets by far the most brutal death out of all of the Blood Tribe: Grease ties him to a pillar with the Rose Bottle's vines, then fills him full of holes with bullets from behind. Given he's the one who's responsible for Kasumi's death it counts as Kick The Son Of A Bitch.
- Kick the Dog: Kasumi's conversion into a Smash despite her physical state making her death certain? That was his idea and he brags about it to Ryuga.
- Megaton Punch: In his Lost Smash form, his fists can create black and white shock waves, like during his first fight against Cross-Z.
- No Name Given: 'Mitsuomi Gobara' is the name of the human who he possessed and replaced. Unlike Evolt and Killbus, his real name is never actually revealed.
- This Cannot Be!: A more understated one than the other three: his last words are "No way!" as Grease kills him.
Killbus
Killbus/Kamen Rider Killbus
Portrayed by: Anri Katsu (voice), Gaku Shindo (physical appearance), Yasuhiko Imai (suit)
Are you Ready? Spider! Spider! Killbuspider!
The king of the Blood Tribe and Evolt’s older brother. He arrives searching for Evolt to reclaim Pandora's Box that Evolt stole from him and mistakes Ryuga for his brother.
- Agent Peacock: He spends most of the movie in the form of a flamenco dancer and twists and turns like he's dancing with every movement. He’s also the King of the Blood Tribe and the strongest of all of them.
- Ancient Evil: He is Evolt’s older brother, and like him, millions of years old.
- Authority Equals Asskicking: The King of the Blood Tribe and its most powerful member, surpassing even Evolt and Ino.
- Ax-Crazy: He’s even nuttier than Evolt, which is saying something. Where Evolt simply wanted to become the strongest, and only, being in the universe, Killbus wants to annihilate the universe and himself in a Big Bang because he thinks it’d be a cool way to die.
- Beyond the Impossible: Killbus is said to be stronger than Evolt without any use of the Evol Driver. Also, in addition to being the strongest of the Blood Tribe, he's supplemented his strength by the time he enters Build's New World by devouring several planets while Evolt and the other three survivors were playing puppet masters on Earth.
- Big Bad: He serves as the main villain of the New World Cross-Z V-Cinema.
- Big Brother Bully: The ways he tosses around Banjo and Evolt along with his general demeanor are a lot like that of a bully picking on someone smaller.
- Brains and Brawn: The "brawn" to his brother's brain. While Evolt makes use of intricate plans, Killbus just muscles through everything with his massive might. Given how powerful he is, he doesn't need to plan, although Evolt's cunning is part of what leads to Killbus's downfall.
- Cain and Abel: The Cain to Evolt's Abel. He tries to kill Evolt by absorbing him into the White Pandora Panel to use as energy for a new Pandora's Box, but Evolt gets the last laugh by fusing with Cross-Z to defeat him.
- The Caligula: The king of the Blood Tribe is not a very sane fellow, even by the standards one would probably expect from a race of sadistic Planet Eaters. He is even the one responsible for the destruction of their home planet, which he did purely to satisfy his bloodlust.
- Death Seeker: Not only he wants to destroy the entire universe, but also himself along with it.
- Devour the Dragon: When Cross-Z Evol starts getting the upper hand in their battle, he powers himself up by absorbing the Clone Smash that he spawned to fend off Grease and Rogue.
- Dying Moment of Awesome: His end goal is to give himself one. Unfortunately, dragging the entire universe down with him is the only death he deems awesome enough for himself, and he won't settle for anything less.
- Evil Knockoff: Before he swipes the Killbuspider, he simply uses Best Matches to become Build. Even in this form he’s much stronger than Ryuga and holds the upper hand in a fight against Evolt’s Blood Stalk form.
- Evil Uncle: He's Evolt’s brother and thus Ryuga’s uncle.
- Eviler than Thou: To Evolt of all people. Evolt does think highly of humans (for mostly twisted reasons, albeit) while Killbus thinks everything is beneath him. Even Evolt is shocked at how destructive he is. If nothing else, Evolt at least wants to survive killing everything else, whereas Killbus wants to kill himself and the Blood Tribe off too.
- Evil Is Hammy: Killbus outdoes every other villain in the series in this regard. Nearly every word out of his mouth is delivered hammed up.
- Faux Affably Evil: Killbus can be pretty jovial and the way he greets Evolt again is just like a brother talking to a sibling he hasn’t seen in a while, though it’s easy to see he’s just a psychotic planet destroyer. And he never drops his cheerful attitude even when picking on Evolt like a bully.
- Finishing Move: Killbuspider Finish: Killbus binds his enemy with webs, immobilizing them before striking them with gigantic spider legs. Alternatively, he can throw the immobilized enemy into the air and delivers a spinning heel kick to them.
- For the Evulz: Killbus' only motive for destroying things is because he likes destroying things. To quote Evolt, “he’s a hedonist with a love of destruction”.
- Genocide from the Inside: He’s responsible for there being so few Blood Tribe members in the present day, having killed most of them when he destroyed their homeworld.
- Godzilla Threshold: Killbus just being there is enough to get Evolt to work with Ryuga and Team Build. Granted, this is mostly because Killbus' desire to kill literally everything includes Evolt, but also even himself.
- Greater-Scope Villain: Of the entire Build series. Killbus’ destruction of the Blood Tribe’s homeworld and his orders to the remaining members of his tribe is what drove Evolt and his minions to steal Pandora's Box and eventually pick a fight with Queen Vernage, setting the events of the series. Not bad for a character who only appears in one movie, huh?
- In an even wider sense, his destruction of Planet Blood is what made Evolt able to be a galaxy wandering Planet Eater in the first place. Considering Evolt was behind nearly every other villain in the TV series, this makes Killbus responsible for all of that by proxy.
- Identity Impersonator: Upon defeating any foe or seeing anyone that interests him, he steals their look. For the majority of the film he takes on the look of a flamenco dancer he saw on TV.
- The Juggernaut: Killbus thrashes every obstacle in his path, and attempts to stall him don't do so for very long.
- Karmic Death: Dies, not in a universe destroying bang like he wanted, but at the hands of two beings he previously deemed inferior to himself (Banjo and Evolt).
- Large Ham: Just like Evolt, he's extremely over the top and loves attention.
- Last of His Kind: Following Evolt’s demise, Killbus is the last known member of the Blood Tribe. At least until Evolt comes back and helps kill him.
- Laughing Mad: He laughs like a hyena while fighting.
- The Man Behind the Man: Evolt states that Killbus is the one who gave out the order to destroy planets to the other members of the Blood Tribe, making him responsible for Evolt and the other surviving Blood Tribe members’ planet-destroying sprees.
- My Little Panzer: The Killbuspider was originally meant to be a children’s toy.
- Nice Job Fixing It, Villain: Using Ryuga to recreate Pandora's Box near the start of the movie causes a ripple effect that restores the memories of everyone who was subject to the Nebula Gas experiments.
- One-Man Army: Killbus is strong enough to destroy entire planets on his own, and thus doesn't need an army or henchmen to back him up. The only time he enlists any form of assistance in a battle is when he summons Smash to hold off Kamen Riders Grease and Rogue while he fights Cross-Z and Evol, and even then they're extensions of himself.
- Psychopathic Manchild: Even more so than Evolt. His behavior is an alien equivalent to a sadistic schoolyard bully.
- Red Is Violent: Killbus’ Kamen Rider form is almost entirely red and his human guise wears mostly red clothing. Naturally, he is a pretty destructive fellow.
- Replacement Flat Character: His personality is Evolt's, but with his Large Ham and Omnicidal Maniac tendencies ramped up tenfold and lacking in Evolt's cunning and what little depth he received over the course of the series. He's so bad that Evolt works with Team Build for his own sake.
- Say My Name: Banjo Ryuuuuuuuga!
- Spell My Name With An S: His name can be spelled as either “Killbas”, “Killbus”, or “Kilbus”.
- Spiders Are Scary: He has a distinct spider theme to his Rider form, filling out the classic rider monster trifecta. Similarly, his Transformation Trinket the Killuaspider is essentially the Cross-Z Dragon but a Spider.
- Stronger Sibling: He’s even more powerful than his younger brother. Evolt has never beaten him in a straight fight, seemingly even with access to Black Hole or his monster form. As mentioned previously, Kamen Rider Evol is in the running for one of the most powerful riders of all time. And using just Build’s Driver and a few extras, Killbus is able to curb stomp Evol Phase 1: Cobra and Cross-Z Magma (who is strong enough to at least briefly hinder Evol Phase 4: Black Hole). Killbus also states that in the millions of years they’ve been apart, he’s been wiping out and absorbing planets, making him even stronger. Fair to say we’re all glad there wasn't an Evol Driver handy for him to try out.
- Even before that, he managed to put Cross-Z, which in its last appearance in series overpowered one of the Kaisers, up against the ropes with RabbitTank, and do the same to the similarly superior Blood Stalk with FireHedgehog.
- Suicidal Cosmic Temper Tantrum: Takes his omnicidal mania one step further than his brother. Evolt wants to travel from planet to planet, torturing their inhabitants for his own amusement before eating their planets to continue his own evolution. Killbus wants to just wipe out the entire universe, including himself. Evolt thus turns against Killbus to ensure his own survival.
- Taking You with Me: Killbus wants to do this with the entire universe so he can die in a new, universe destroying big bang.
- The Hedonist: Evolt describes him as 'a hedonist in love with destruction,' which essentially translates to Killbus' entire existence being devoted to destroying everything For the Evulz. Including himself.
- Villainous Lineage: Both he and his brother turned out as sadists with a love of destruction. Makes you wonder what their parents must be like.
- Walking Shirtless Scene: While copying the form of Satoshi Kakizaki, the flamenco dancer he saw on TV.
- Where I Was Born and Razed: He destroyed his own home planet.
Down Fall
An international radical terrorist organization led by Simon Marcus and the main antagonist of Kamen Rider Build NEW WORLD: Kamen Rider Grease as they kidnap Misora Isurugi and seek to take over the world. Simon Marcus
Simon Marcus
Portrayed by: Michael Tomioka
One of the leader of the terrorist organization Down Fall, Simon Marcus is a British prime minister and a high-ranking official of the United Nations who seeks to dominate the world by taking over Japan and its Rider technology.
- Boss in Mook Clothing: When transformed into Phantom Crusher.
- The Leader: Of Down Fall before being betrayed by Keiji.
- You Have Outlived Your Usefulness: Simon is later betrayed and shot by Keiji near the end of the film.
Phantom Crusher
Phantom Crusher
Portrayed by: Various
- Animal Motif: Spiders, like Killbus.
- Butt-Monkey: The messy-haired blond that attacks Grease early on in the film really can't get a break, constantly being harassed throughout the film even while transformed. It isn't until Metal Build gets Grease down to his last legs that he's able to land a solid hit at all, though this is quickly invalidated by both being disintegrated to become parts for Phantom Build, and Phantom Build's defeat at the hands of Perfect Kingdom.
- Elite Mooks: While average Hard Guardians are tough on their own, any Phantom Crushers take this one step further by having an ability to negate the transformation of Kamen Riders.
- Energy Absorption: They can absorb Nebula Gas from Riders, negating their transformation. When one of them attempted this on Kazumi and the Three Crows, it doesn't work.
Keiji Uraga/Kamen Rider Metal Build
Keiji Uraga/Kamen Rider Metal Build/Zebra Lost Smash I/Kamen Rider Phantom Build
Portrayed by: Tamiyasu Cho (live), Kosuke Asai (suit)
Are you Ready? Uncontrol Switch! Black Hazard! Yabei!note
SPOILERS
A former Faust scientist and an associate of Shinobu Katsuragi who was previously died as a result of their Lost Fullbottle experimentation. He is the true leader of Down Fall and the main antagonist of Kamen Rider Build NEW WORLD: Kamen Rider Grease.
- Ascended Extra: Like Yui from the previous Build NEW WORLD, he is one of the victims that Evolt used to make one of the four Lost bottles he already had.
- Back from the Dead: Just like Yui, he was originally killed in the World of Build but was revived when the new world was made.
- Big Bad: He is the main villain of the film.
- Curb-Stomp Battle: Completely decimates the Hokuto Three Crows in a three on one battle, and puts them in critical condition. He then takes down a fresh and uninjured Kazumi just as easily.
- Dark Is Evil: He is a double abiotic Rider, dyed in Hazard black.
- Disappears into Light: Keiji's fate after getting killed by Kazumi, with nothing but the White Pandora panel left.
- Evil Counterpart: To Yui Mabuchi, of all people. Both Yui and Keiji were forcibly mutated into Lost Smash to be used to harvest the Lost Fullbottles. The key difference is that Yui managed to maintain her morality while Keiji took a running dive off the slippery slope.
- Metal Build as well as its upgrade Phantom Build is this to regular Build, as it represents the biggest fear its creators had when developing the Rider System: that would be used as a weapon of war to terrorize the people it was created to protect. This is even lampshaded by the Hokuto Three Crows, especially Shuuya/Aoba, when Metal Build is basically Build Hazard Form, the only form to instill fear into others instead of inspiring hope. This is also reflected in him using two Tank bottles, as the abiotic half of Best Matches represents something that destroys the biotic half, something Sento defies but Keiji embraces.
- Evil Knockoff: Metal Build is an absurdly-durable knockoff of Build TankTank (though In Name Only since it doesn't have the extra armor), created using the comparatively simple solution of spoofing the Tank Fullbottle twice and then inserting them into the Build Driver.
- Finishing Move:
- Hazard Attack: Metal Build jumps into the air and crashes down to his target with a double knee drop, grinding down the enemy with dark blue-colored energy tank treads.
- Hazard Finish: Metal Build performs a roundhouse kick that generates an energy tank tread that is capable of hitting multiple enemies. As Phantom Build, he also fire missiles before performing two roundhouse kicks instead.
- Foil: Relating to above, Uraga is also this to the main user, Sento Kiryu: they are narcissistic scientists but with different ideologies on how mankind should benefit the Rider System technology. Their face are also altered (Sento was modified from his original face (Takumi Katsuragi to Taro Satou) while Uraga gained a large burn mark on his face), as well as their appearances when using a Hazard Trigger to assume an armored Hazard Form are opposites of each other; whereas Build uses either Rabbit or Tank armor parts as bright colors that instills heroism, Metal Build merged with a Phantom Crusher, a monster Mook olive color resemble army fighters and war. Finally, their means of stabilizing the Hazard Trigger are also contrasted in their complexity: Sento needed to create an entire new set of armor and separate device to double up on biotic/abiotic Fullbottles, while Keiji simply spoofs the Tank Fullbottle twice and dons the Hazard Body with no changes besides two grey Tank eyes.
- Fusion Dance: Uses the White Panel to fuse with a Phantom Crusher's essence and becomes Phantom Build.
- History Repeats: Once again, Kazumi's opponent in a movie is related to the Zebra Lostbottle.
- It's All About Me: Keiji's primary motivation is that he felt his genius was overlooked in the Old World and now he wants to be acknowledged as the powerful genius he views himself to be. He completely rejects Kazumi's ideals of friendship based on his past of being hated and feared because of the scarring he received from serving as a Lost Bottle sacrifice, stating that all that mattered was power granted by technology. Kazumi even said that he pitied him and asked him if he had always been alone. Keiji does not react well to this.
- The Starscream: Keiji would later betray and kill Simon after his plans near fruition.
Others
Yui Mabuchi
Yui Mabuchi/Scissors Lost Smash I
Portrayed by: Mariya Nagao
A mysterious woman who is searching for Ryuga Banjo in Kamen Rider Build NEW WORLD: Kamen Rider Cross-Z.
- Ascended Extra: She’s one of the victims that Evolt used to make one of the four Lost bottles he already had.
- Back from the Dead: She was originally killed in the World of Build but was revived when the new world was made.
- Defrosting Ice Queen: She is very cold to Ryuga after regaining her memories. Well when you were ignored by a Kamen Rider when you were in trouble and then captured which led to being experimented on and then killed, you would be rather cold too. She comes around at the end of the movie.
- Friend to All Children: Comes with being an elementary teacher. Part of her grudge against Banjo is by ignoring her and her students in their time of need, they were also experimented on and they’re still in a coma in the new world.
- Rescue Romance: She gains feelings for Banjo when he protected her from Killbus and later Evolt.
- The Resenter: She spends a good part of the movie hating Banjo. Because he didn’t help her and her students, it lead to her being experimented on and then killed to make a Lost Bottle. It doesn’t help that he explains when he first became a Kamen Rider, he was still self-centered that he wasn’t in the mindset to help the people around him. As such she thinks he only cares about himself. It’s Misora and then Banjo later saving her from Killbus while he was weakened that made her change her mind about him.
- Ship Tease: With Banjo. The end of the movie has her giving him a big hug, kissing his cheek and helping him selling Sento's inventions, with Sento even calling their outing a date.
