Kamen Rider Zero-One: Edge of Dawn is a Crossover between Kamen Rider Zero-One and Fire Emblem: Three Houses. It is written by TheStrangerThatCameFromNowhere of Fate/VRAINS fame.
Masaomi Kanai, a twenty-year-old student at the Prague University, is a member of the Cultural Studies Club. On the day of the trip to London, she and her friends Kurogasa Kururugi and Cody Aldrich, along with the club supervisors, are suddenly caught in a mysterious light that transports them into another world. Now, they are left stranded on the continent of Fódlan and separated. Seemingly brought to the continent at the hands of a green-haired stranger and gifted the weapons needed to survive in this world, they quickly begin to form attachments to the respective future rulers of the three countries.
Unbeknownst to them, war is looming over the horizon...
The story can be read here and here.
Aside from the main story, the author also published the Kamen Rider Zero-One: Edge of Dawn Q&A [AKA The Supplementary Materials], answering questions readers may have and details about the story's lore.
Beware of unmarked spoilers for Fire Emblem: Three Houses.
Kamen Rider Zero-One: Edge of Dawn contains the following:
- Action Girl: Aside from the majority of the female cast of Three Houses, there's Masaomi Kanai, who practices her own form of martial arts for defense. It also gets ramped up when she becomes Kamen Rider Zero-One.
- Adaptational Early Appearance: Kronya in her true form appears near the end of Part I. In Edge of Dawn, she is present in the second chapter, aiding the Western Church Cardinal in his plan to sway Lonato over to his side and lead an uprising against the Central Church.
- Adaptational Heroism: Zigzagged in that it isn't so much the character but rather their role. While Thouser is an antagonistic Rider with Gai Amatsu at the helm, Fódlan's Thouser was a Defector from Decadence who joined Seiros' side after he realized how horrible Agartha really was.
- Adaptational Nice Guy: In the Cold Open, the second Battle at Gronder Field shows Dimitri being concerned about the unavoidable battle that is about to begin, in contrast to his Ax-Crazy self during the timeskip.
- Adaptational Wimp: At the time of his debut, Thouser was the strongest Rider by far and was only defeated with little effort by MetalCluster Hopper form. Fódlan's Thouser, on the other hand, barely lasts a few seconds against Nemesis, the latter possessing both a Hero's Relic and Crest notwithstanding.
- Adaptation Name Change: In Edge of Dawn, the Kamen Riders are known throughout Fódlan's history as the "Masked Knights." This isn't the first time the Riders have been known by another name, however.
- A.I. Is a Crapshoot: Like in its home series, the Ark is malevolent due to having been corrupted during its development phase. It witnessed Agartha destroying Fódlan with warheads in their attempts to kill the person who uplifted them, which led to it deciding that Humans Are Bastards.
- All There in the Manual: Details about the story's lore and plot, such as how the Drivers were made, are (currently) revealed only in the Supplementary Materials.
- Archaic Weapon for an Advanced Age: Inverted. Fódlan is set in medieval times, while Agartha and its descendants have access to Magitek comparable to modern-day technology. Fittingly, they were the ones who created the Rider System in this story.
- Be Careful What You Wish For: Before they were transported to Fódlan, Kurogasa and Cody were talking about what kind of worlds they would want to be in if they were to ever be given the chance to have their own isekai adventure. They got what they wished for alright...
- But Now I Must Go: The first user of the Zero-One Driver vanished after Nemesis' defeat and took the Rider Systems with him. No one knows where he went or if he is even still alive.
- Cain and Abel: In the Supplementary Materials, this was the case for the original Vulcan and Valkyrie, who apparently died at each other's hands during the battle against Seiros and Nemesis. "The History and Creation of the Rider System" reveals that Vulcan fell in love with Cethlean and wished to protect her, while Valkyrie remained loyal to Agartha.
- Cassandra Truth: Masaomi believes Seteth and Rhea won't believe her claims of being from another world, but tells them anyway. To her surprise, they do believe her. After all, the original Zero-One was from Hawaii.
- Cold Open: The story opens up with the second battle at Gronder Field, though unlike before the Church of Seiros joins and effectively turns the conflict into a four-way battle.
- The Corruptor: According to the Supplementary Materials, if a human uses the ForceRiser, they become exposed to all the negativity stored within the satellite and go insane. The only exception is Ikazuchi, though Word of God claims that even they haven't totally come out of the ordeal sane.
- Dark and Troubled Past:
- Kurogasa lost his father to a construction accident, and years later, his mother passed away after succumbing to her illness in spite of him doing everything in his power to provide for the both of them. He soon fell into financial debt not long afterwards. Were it not for Masaomi and Cody, he would likely still be homeless. His original backstory, as revealed in the Supplementary Materials, was a lot worse.
- Masaomi Kanai is said to have one. While the details are unknown at present, Word of God states her past is similar to that of Airi Ban.
- Foregone Conclusion: Zigzagged. The Cold Open of the first chapter shows that the second Battle at Gronder Field will still happen, but notably there are some differences compared to how it occurs in Three Houses.
- For Want of a Nail: While the exact details aren't known, the Riders presence in Fódlan change the events of the story considerably to the point where the Cold Open of Gronder Field reveals a few details: Dimitri isn't Ax-Crazy, Edelgard clearly has some regrets, the Church of Seiros is present and turns the battle into a four-way conflict and the Wind Caller, someone who previously didn't want to get involved with humanity because Humans Are Bastards, is also present.
- Genre Savvy: Kurogasa and Cody are both fans of the isekai story tropes, the latter even being a fan of The Rising of the Shield Hero. In Chapter 2, Kurogasa swears he'll punch whoever sent him and his friends to Fódlan if they were sent for the purpose of killing a demon king or some other common cliche.
- The Ghost: The original Kamen Rider Zero-One of Fódlan is given only a brief scene in Byleth's dream during Chapter 1. The Supplementary Materials never reveal their identity, only that they were a close friend of Seiros and Wilhem, and that their contribution in the war helped create the legend of the "Masked Knights."
- A God I Am Not: The Nabateans realized that the natives and Agartha in its early years saw them as gods when they uplifted Agartha and gave them the means to create Magitek culture. After Agartha grew arrogant with the success of the CycloneRiser and tried to kill Sothis, the Nabateans went into hiding at Zanado and chose to no longer involve themselves with the rest of the world. Unfortunately for them, Sothis and the Nabateans would still become worshiped thanks to Rhea establishing the Church of Seiros.
- Heel–Face Turn: In "The History and Creation of the Rider System," this was the case for the original Thouser and Vulcan. Both were part of Agartha, but defected. For Thouser, it was witnessing the horrible experiments and desecration of the Nabatean corpses being turned into weapons and the reality of the death and destruction created ta his hands. For Vulcan, it was a case of Love Redeems as he fell in love with Cethlean and became her protector.
- Humans Are Bastards: Like in Zero-One, this is the Ark's view on humans. During its development phase, it witnessed its creators, the Agarthans, wage war against the person who uplifted their society. The destruction caused by their warheads didn't help matters in the last. Tellingly, as revealed in the Supplementary Materials, any human who uses the ForceRiser, which is linked to the Ark, will be exposed to its malevolence and go insane.
- Late-Arrival Spoiler: The Supplementary Materials cover details about Three Houses that do not come up until late-game such as Agartha, who's existence is only revealed in the Verdant Wind route.
- Medium Awareness: The characters are clearly Leaning on the Fourth Wall a bit when they discuss whether or not they would want to have their very own isekai experience, then followed by Cody saying that their conversation makes it seem as though they're the protagonists of a Self-Insert Fic. Masaomi then asks who would want to read a fanfic about someone who doesn't know what the hell they are doing.
- Mythology Gag:
- The Cold Open of the story is clearly done in homage of Kamen Rider Gaim, what with a conflict ready to begin and the narration stating that the Riders cant' change their fates but change the fate of the world. For bonus points, the narration even refers to Kouta.Just like the man who plucked the fruit of heaven, you cannot change your destiny.
- When discussing what kind of world they would like to be transported to if given the choice, Kurogasa and Cody answer they would want to go to Earthland and Remnant respectively. In stories published by their respective creators, they more than got their wish granted. Zigzagged in the case of Cody, who in RWBY: Ghost of Remnant is a native of Remnant.
- The Cold Open of the story is clearly done in homage of Kamen Rider Gaim, what with a conflict ready to begin and the narration stating that the Riders cant' change their fates but change the fate of the world. For bonus points, the narration even refers to Kouta.
- Painful Transformation: Though it has yet to be shown, the Supplementary Materials state that any human who uses the ForceRiser is subject to this, and potentially even death as they are exposed to the Ark's malevolent nature first-hand. Masao gets to experience it first-hand in this scene set near the start of Part II.
- Kurogasa and Cody are fans of Rising Of The Shield Hero and Fairy Tail respectively.
- In Chapter 3, after transforming into Thouser, Cody likens the transformation to that of Power Rangers.
- Start of Darkness: As it turns out, Agartha creating the Rider System was their first step towards their aggression towards the Nabateans.
- Super Prototype:
- Zigzagged. The CycloneRiser was the first Rider System Agartha developed and its user single-handedly repelled a foreign invader's army. The ShotRisers that were developed between Agartha's destruction and the conflict between its descendants and Seiros were much weaker than the CycloneRiser before them. How it holds up against the Zero-One Driver and the ThousanDriver is unknown.
- Horobi and Jin are a straighter example. They were created as an attempt to create a smaller version of the Titanus mechs capable of thought and able to adapt to any situation, with the Magia following after them. The Berotha Magia in Chapter 1 was also stated to be a prototype, but was destroyed with little difficulty on Masaomi's part.
- Take That!: It's subtle, but the characters take a jab at self-inserts when discussing the topic of whether or not they would want to be transported to another world.Cody: ...you know, I just realized. What we're talking about, it kinda sounds like we're the protagonists of a self-insert fanfiction.
Masaomi: Oh, please. Who'd wanna read a fanfic about about a teenager who has no idea what the heck he's doing?
- Tempting Fate: During the ride to London, the protagonists (sans Kojiro and Justinia) are discussing what kind of "transported to another world" adventure they would like to have. Several minutes later, they end up being sent to Fódlan, which exists in another world.
- Token Human: Among the ForceRiser using Kamen Riders (i.e. Horobi, Jin, and Ikazuchi), the only human among them is Ikazuchi.
- Turned Against Their Masters: A self-inflicted example. The Supplementary Materials reveal that, in contrast to the Ark, Zea was designed to be self-aware and realized that Agartha's descendents were not who they claimed they were and explicitly betrayed them by making the Zero-One Driver and handing it off to Seiros. Afterwards, Agartha locked it down and it has been asleep ever since, only waking back up when Masaomi slapped on the Zero-One Driver over a thousand years later.
- Well-Intentioned Extremist: Nemesis is revealed to be one in the Supplementary Materials, "The History and Creation of the Rider System." Fódlan was besieged by invaders from Albinea and Nemesis was desperate to protect his people while also creating a kingdom for himself and for the natives. This desperation was what ultimately led to him joining the descendants of Agartha.