As expected, the 5th Holy Grail War has arrived in Fuyuki City, and seven teams of Masters and Servants prepare to battle for the fabled Holy Grail. But unbeknownst to all, a new element has been added into the experiment. Shirou, still a below average mage, has recently achieved his dream of becoming a superhero. Armed with a high IQ and gadgets that even skilled mages can't begin to imagine, ends up fighting Lancer before Saber is summoned, leading to his abilities being discovered by the other Masters and Servants. As each party begins to focus on his strange gear, another party, one that Shirou has been fighting for over a year, discovers the existence of the Grail War and seeks to use it to their advantage...
FateBuild: The Mechanical Magus
is a Fate/stay night and Kamen Rider Build crossover by Tailsmo4ever.
This work provides examples of:
- Adaptation Amalgamation: The story borrows elements from all three of Fate's timelines, which has interesting effects going forward. In particular, while Shirou and Rin's teamup leans closer to how they allied in Unlimited Blade Works, Sakura's issues from Heaven's Feel are brought up early on and (mostly) sorted out, as well as Rin correctly deducing that Sakura is Rider's true master.
- Adaptational Badass: Thanks to the gadgets he invented, Shirou has already achieved his dream of becoming a hero, even being able to fight Lancer.
- Adaptational Intelligence: Shirou is as average as average can be in Fate. In this story, he's an inventor and excels in math and physics in school, outdoing Rin (but is still average in other subjects).
- Adapted Out: Since most of Zouken's Crest Worms within Sakura are killed by exposure to Nebula Gas, which is followed up by having Rin and Shirou rescue Sakura and give her a pep-talk to address her insecurities, it's looking like the Shadow won't be making an appearance.
- Age Lift: Mimi Katsure is a child around Ilya's age in her home series (where Ilya is actually as old as she looks). Here, she's implied to still be around the same age as Ilya, so when Shirou meets her in chapter 7, she's an adult.
- The Bechdel Test: Parodied. Shinji catches Shirou and Issei talking about Rin and (unknown to them at the time) Caster, declaring that they both failed the test.
- Beyond the Impossible: The Magic Side is shocked that Kamen Rider Build is able to survive Noble Phantasms and succeed in taking one of Heracles's lives which only high-level Servants are thought only be able to do, especially since Build is a piece of newly created technology, as per the laws of the Nasuverse technology cannot affect magical entities unless modified with magic, and Older Is Better. If Build still retains its origins as being created from extraterrestrial technology, then it might actually Subvert this, due to the nature of how extraterrestrials interact with Earth in the Nasuverse.note
- Broken Masquerade: This is a serious problem involving Faust, as their actions run the risk of allowing Muggles to find out about the Moonlit World. Even worse (from a Mage perspective) is that initially, Faust isn't even trying to break the masquerade — it's just that their conflict with Kamen Rider Build is leading them dangerously close to the truth.
- Composite Character: A few so far.
- Shirou is combined with Sento Kiryu AKA Kamen Rider Build.
- With some unsettling revelations about her, as well as Sakura taking the role of the Burn Smash, it's implied that Rin would be based around Ryuga Banjo/Kamen Rider Cross-Z.
- Creator's Culture Carryover: Downplayed - the author includes a few references/jokes that would make more sense if the story was set in North America (such as having Taiga claim that Shirou would start smoking marijuana after going down the slippery slope while letting Saber stay at his house), but otherwise the jokes and social elements are accurate to Japan.
- Dark and Troubled Past: Mainline Shirou had the sole survivor thing of the Great Fire, but that was a mercy compared to Faust experimenting on him. Ironically, it was the Great Fire that saved him from Faust.
- Dirty Old Man: Bloodstalk is this when he reacts perversely with Rider much to the latter's disgust. Rin even calls him that.
- Dramatic Irony: In the very first chapter, Issei mentions how his teacher, Soichiro, has invited a woman over to Ryudou Temple and has gotten engaged to her. Shirou wonders if it was Love at First Sight, which Issei shoots down. Readers will know, though, that Soichiro did have Love at First Sight with the woman in question (Caster).
- Enemy Mine:
- Shirou and Rin join forces to not only handle the other Masters and Servants but to also stop Faust from getting the Holy Grail for their own nefarious purposes.
- After Blood Stalk fills Homurahara with Nebula Gas as a test of its power, most if not all the Masters and Servants decide to prioritize dealing with Faust than the Holy Grail War, now seeing the threat they can actually pose.
- Entertainingly Wrong:
- Pretty much all of the Magi in the Holy Grail War operate under the assumption that Shirou is using a Mystic Code. Not that far off an assumption, but also completely wrong. Justified as Magi normally believe that magic triumphs over science.
- Night Rouge at first believes that Berserker is a clone of the original Heracles created through lost DNA. He soon drops the theory after learning about the Holy Grail War.
- Fun with Acronyms: The Smash are given one: Specially Mutated Alienized Super-Humanoids.
- For Want Of A Nail:
- Reika Rikudou, one of the main antagonists of Fate/Apocrypha, is revealed to be one of the members of Faust due to Great Grail War not existing.
- Mimi Katsura, one of Illya's school friends from the Miyuverse, appears as an adult and a doctor at a hospital.
- Fusion Fic: The setting is a cross between the Nasuverse, and the Kamen Rider Build canon.
- Gas Leak Cover-Up: As in canon, this is how people being drained by servants is being covered up, but it's also being used to explain away attacks by Smash. Rin takes notice, and immediately realized something was up since these started before the summoning of any servants that could explain what the coverup was for.
- Godzilla Threshold: Faust's willingness to challenge Masters and Servants in broad daylight and, in general, deliberately ignore the masquerade is enough of a problem that Kirei decides to call a temporary truce until Faust is defeated, lest the Association decide to get involved.
- Head-Turning Beauty: Shirou notes that Reika's looks will make any men go insane with lust.
- He Knows Too Much: Rin is scared that Faust knows about the Holy Grail War, knowing full well that the Mages Association will destroy the entire city to ensure the Holy Grail is safe from outsider's hands, especially those that belong to a terrorist group.
- Hopeless with Tech: Rin as usual. Having being taught by mages who hate technology, Rin has distanced herself from modern appliances at a young age which is why now, she is helpless when it comes to Build, the Full Bottles and Faust.
- Ironic Echo: Blood Stalks says Build's catchphrase as he's flooding Homurahara Academy with Nebula Gas.
- Know When to Fold 'Em: While he does complain about it, Shinji ultimately takes Rider's advice to flee Homurahara when Blood Stalk floods the campus with Nebula Gas.
- Kryptonite Factor: Nebula Gas does something that interferes with Magecraft, as it allowed Blood Stalk to trade blows with Saber, despite the latter using Excalibur, which should ignore non-magical defenses. It also seems to be toxic to Zouken's Crest Worms.
- Magic Versus Science: The theme of the story - one half of the cast comes from an Urban Fantasy setting and deals with magic in the modern world, while the other half are from a Post-Cyberpunk setting focused on trying to gain an alien artifact and battle science-derived monsters. Notably, it's explicitly shown that Nebula Gas has negative effects on Magi. It's also poisonous to Zouken's Crest Worms.
- The Masquerade: Zigzagged — while the magic side of the crossover takes pains to hide their actions, the technology side could care less if people see their forces in action as long as the identities and allegiances of those forces remain hidden. Rin is terrified by this, since it risks causing the magic side to undergo a Broken Masquerade, which could lead to Fuyuki being destroyed to salvage said masquerade.
- Mundane Utility: Rin requests Shirou to use the Diamond Full Bottle to produces gems for her since she needs them as ammunition and those things are expensive.
- Mythology Gag:
- When Shirou asked Saber if she was Jeanne D'Arc, she has a negative reaction. This is because it was a reminder to the Fourth Grail War's Caster who always called her Jeanne both because she was an Identical Stranger and because he was a deluded psycho.
- Reika nearly traps and tries to kill Shirou the same way she tried to kill Seig; by pulling a Wounded Gazelle Gambit on him and shooting him point-blank in the chest when his guard is down. Unlike Seig, Shirou had his armor on, but his reaction makes clear that it still hurt like hell.
- Saber and Night Rouge's battle and argument makes a nod to a particular ending in Heaven's Feel, notably one where Shirou goes through with killing Sakura.Night Rouge: One cannot make an omelet without breaking a few eggs. Hard decisions require a mind of steel. To be willing to work for the greater good, sacrifices are required!
Saber: And what will you have left after all those sacrifices? Who will be left when there is no one behind you? Would you even be willing to kill those who are dearest to you?
Night Rouge: I will do what I have to in order to protect this nation! - When Faust is looking over what information they have on Saber, they learn from reika that she was once in Japan ten years prior, and goes by the name Elise Watson. All of this references Fate/Zero, Elise Watson being the cover identity Kiritsugu used to get Saber into Japan.
- While trying to do some research into Shirou's Kamen Rider armor (which she still assumes is a Mystic Code), Ilya wonders if it is related to either the Animuspheres or the Fargos.
- Saber briefly works as a server at Nascota to help Shirou. She did something similar in Carnival Phantasm to get money to buy Shirou a birthday present.
- On the Kamen Rider side, Misora made a brief mention to Emu Hojo's secret alias as Legendary Gamer M during a discussion about online gaming tournaments.
- Just as his father did, Kirei is forced to call a truce during the Grail War to deal with a threat to The Masquerade. But while Risei had to deal with a rogue Master-Servant duo, his son has to face a technological foe entirely unaffiliated with Mages.
- The Needs of the Many: Night Rouge uses this to justify his terrible actions. Saber is enraged after hearing this, having already experienced this brutal ideology through Kiritsugu.
- Not So Above It All: Rin makes a point of keeping an air of nobility around herself due to being the heir of a powerful magus family. All of this promptly goes out the window when Shirou takes her to ride on his motorcycle.
- O.O.C. Is Serious Business:
- Rin likes to present herself as calm, and collected, due to her pride as a Magus and her upbringing. So when her reaction to learning that Shinji raped Sakura, her sister, is to call him a son of a bitch and immediately plan a direct attack on his house with little to no concern for strategy at first speaks volumes of just how much Shinji enraged her.
- Archer actually smiles when Shirou and Rin promise Sakura that they will keep her safe from Zouken and Shinji.
- Outside-Context Problem: Kamen Rider Build, the Smash, and Faust are this for Magic side of things - as Magi consider technology beneath them, they're woefully surprised when facing Post-Cyberpunk entities who can fight them on an even playing field. In turn, the technology side is surprised to fight entities that are straight up supernatural, with the exception of Faust, who have at least on magically sensitive person (Reika Rikudou) among their number.
- Post-Cyberpunk: It carries some themes as the three Governments of Japan have all been shifted into big tech companies; Touto Cyberware, Seito Zaibatsu, and Hokuto Technologies. They rebuilt the sections that were destroyed by the Great Fire, and Shirou has also mentioned selling some inventions to Touto for extra money.
- Pragmatic Adaptation: Since the activation of Pandora's Box would likely set off massive alarm bells for the Mages Association, most of the alien elements of Kamen Rider Build have been modified into being relatively more mundane (the three governments are now corporations, for example). Additionally, the activation of Pandora's Box has been substituted with the Fuyuki Fire, as both happen ten years prior to their respective series' main plot. The only elements that retain their extraterrestrial origins are the Kamen Riders, SMASH, Faust, and Pandora's Box, since there's no way they could be produced by terrestrial technology.
- Red Eyes, Take Warning: Shirou notices Rin's eyes slowly turning red after he tells her what happened to Sakura.
- Reed Richards Is Useless: Averted - Shirou explicitly sells off some of his inventions to Touto Cyberware for money (though since Shirou is just a teenager, it can safely be assumed they haven't had time to mass produce said inventions).
- The Stations of the Canon: Downplayed, as there are a few differences from canon so far (Bazett is still alive, for example), but the beginning of the story follows the events of the Unlimited Blade Works route with only a few divergences. Then Blood Stalk throws things Off the Rails by deciding to perform an experiment at Homurahara Academy, which not only forces Shinji and Rider to ditch their plan to use Blood Fort Andromeda, but also results in Sakura turning into a Smash and, in the process, reveal that she is infested with Crest Worms. This, along with numerous other incidents involving Faust, leads Kirei to declaring a temporary truce to deal with Faust.
- Spared by the Adaptation:
- Canonically, Bazett is killed off by Kirei so that he can steal her command spells and control of Lancer. Here, she's turned into a Smash, but is defeated by Shirou and taken to a hospital to recover.
- In Kamen Rider Build, the host for the Burn Smash, Kasumi Ogura, dies after the Smash Essence is extracted, due to being too weak to survive the transformation. Here, said host is Sakura, and since Sakura has had to endure being used as a living nest for magical parasites for ten years, she manages to survive the Smash Essence's extraction.
- Spotting the Thread:
- Rin figures out that something is up with the Gas Leak Cover-Up, as while the 'gas leaks' could be explained away as servant attacks, they started happening before anyone summoned a servant.
- Saber is suspicious that the Nascita cafe has an advanced lab conveniently set up for Shirou's benefit. Shirou doesn't bother about this since he already has enough problems dealing with Faust and the Smash.
- Rin notices very quickly that Kozuki isn't affected by the Nebula Gas, though he directly tells her that he is a Master before she can put anything else together.
- Strange Minds Think Alike: After Faust's actions disrupt the Grail War and lead to a truce, Zouken and Shinji both consider exploiting the organization for their own goals. They even have the exact same line of thought.Zouken/Shinji: (thinking) As bad as things were before, Faust opened a brand new opportunity for him.
- Tomato in the Mirror: Shirou and Rin are human Smash, which would explain why Rin does not suffer any ill effects of the Nebula Gas. She does not take it well.
- Tsundere: Rin, as always. Misora explictly refers to Rin as one after hearing Shirou mention and describe her.
- Villains Never Lie: Blood Stalk tells Rin he has no reason to lie about her being a humanoid Smash when the truth is much worse.
- Villain Takes an Interest: Both Shinji and Zouken take an interest in Faust after Blood Stalk fills Homurahara with Nebula Gas and forces Kirei to call a truce to the Grail War. Zouken even starts experimenting to see which of his Crest Worms can survive said gas.
- We Can Rule Together:
- Night Rouge offers Saber to join Faust and bring order to Japan. Saber immediately rejects the offer obviously.
- Shinji also makes this offer with Shirou. As in canon, Shirou refuses.
- Wham Episode:
- Chapter 5. Blood Stalk releases Nebula Gas into Homurahara, turning the student and faculty into Smash, with Sakura among their numbers. Additionally, when confronted by Rin and Shirou, Blood Stalk reveals that the Nebula Gas can be absorbed through skin, and that since Rin isn't being affected by it, there's the possibility that she is a Smash. Finally, Sakura's Smash form begins attacking Rin while the latter freezes up in terror over having to fight her sister.
- Chapter 8, "Only I Have The Right To Kill You": Night Rouge turns Ilya into the Mirage Smash, causing her to reveal to Shirou that she is Kiritsugu's daughter. Night Rouge, meanwhile, reveals that he knows who Saber is.
- What If?: A major plot point is how would things progress if Shirou succeeded in becoming a superhero. A major clue is that Archer does not remember ever wearing a red and blue suit of armor.
- You Have GOT to Be Kidding Me!: Rin is exasperated just how ridiculous many of the Full Bottles are.
