Kamen Rider Days is a spinoff of the ZKDTrilogy. It focuses on the adventures of Ryuji Hasuma as he lives in the world and city where VisualNovel/SchoolDays takes place.

Yes THAT VisualNovel/SchoolDays. It all began when the [=ChronoLiner=] Riders crash into this world. Until repairs to their train can be done, the crew decide to stay in this world and enroll themselves in school since they have deaged. This is when Ryuji meets our favorite yandere, Kotonoha Katsura. The two form a friendship after he defends her. When they discover the fate of the characters of this world, the [=ChronoLiner=] Riders decide to stop it, with Ryuji electing himself to look after Kotonoha. After saving her life from a suicide attempt, Ryuji persuaded her to hang out with him and his friends while at the same time protecting her from bullies. On the last night of the school festival, romance blossoms as Ryuji and Kotonoha kiss, but on their first day Kotonoha finds out the truth when Ryuji is injured by Sauron. He is forced to leave but days later he returns to her and states that he is staying as this world's Kamen Rider, Kamen Rider Ifrit.

Kamen Rider Days takes elements of Series/KamenRiderDenO since it involves time traveling train and Imagin, but the stories are actually pretty original, focusing a lot on Ryuji's growth and development with Kotonoha. Also, Kotonoha herself develops into a more dynamic character. The other characters of VisualNovel/SchoolDays are also featured.

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This Fanfiction contains examples of:

* ActionGirl: Neko with Gekiryuken, which is also an EmpathicWeapon.
* AllGirlsWantBadBoys: Averted, insofar as it's Ryuji's good character underneath the "bad boy" exterior and [[SingleWomanSeeksGoodMan the more compassionate side he shows after certain events that attracts Kotonoha Katsura.]]
* AllLovingHero: Kotonoha is the most forgiving, loving, and kind human being to possibly ever exist, with a few exceptions. Her Rider form is named after the Japanese word for "angel" and even resembles an angel!
* AnimalMotifs: Kenzaki has his Wolf-Fist Gekijuken fighting style to project this image.
* AntiHero: Ryuji's Type III. He's definitely a good guy and far more heroic and decent-minded than he likes to let on, but he's also rude and disrespectful and violence is often his means of communicating his displeasure with someone or something. This applies to Kenzaki as well. He's a bounty hunter, but he's a good guy through and through. Kat is either a Type IV or a Type V, depending on the particular storyline and her moods. At her best, she's incredibly insensitive to others' feelings but ultimately well-meaning. At her worst, she's a borderline sociopath with serious empathy issues.
* ArchEnemy: Sauron, the "Humanoid Abomination" leader of the Horrors, fiend spirits that latch onto the darkness in human hearts and use it to corrode their souls and warp their bodies and minds. She is this to Ryuji/Ifrit, as well as Kat and Neko Hasuma.
* BelligerentSexualTension: It's possible to see this between Kat and Kenzaki Tsukuba, Neko's lover-turned-husband and thus Kat's brother-in-law. Kat doesn't like Kenzaki at all, and the feeling's mutual, but the way she keeps going after him . . .
* BerserkButton: Hurting Kotonoha in any way, shape, or form earns you Ryuji's eternal enmity . . . even if Kotonoha wants you spared. For her sake, he won't kill you or do anything really bad to you, but it's almost guaranteed that he'll never like you. Warren too if you hurt Ryuki, or anyone else in his charge. That will get you the most merciless beating you could ever ask for. Might be better to save yourself some time and pain and surrender, or just put one in your head. This also applies to Kenzaki when anyone hurts his Neko and also Kotonoha has this too when anyone says anything bad about her love, Ryuji.
* BewareTheNiceOnes: Kotonoha may be "The Messiah," but there are reasons you shouldn't mess with her or someone she loves (like Ryuji). Neko may be demure and sensitive and caring, but don't make her angry. You won't like the result. At all.
* CharacterDevelopment: From a ChaoticEvil EnemyWithin to a ChaoticNeutral Hired Gun to a ChaoticGood HenshinHero . . . even if he won't admit to being any kind of "good."
* ChromeChampion: Kenzaki, thanks to his metallic skin.
* ClickHello: How Neko met Kenzaki; he had a gun in her face and threatened to kill her because he thought she was the same person that murdered his family. By the time we see them in-story, they've long since gotten over that. Too bad Kat hasn't.
* CloningBlues: Of a sort. Since Ryuji technically is a replication of another person (Ryuki), he struggles a lot with the feeling that he isn't a real person, something his closer allies have tried to disabuse him of.
* CommonEyeColors: How you can tell Neko and Kat apart; Neko has [[InnocentBlueEyes blue eyes]] and Kat has [[RedEyesTakeWarning red eyes]].
* DarkAndTroubledPast: Losing his brother, and then said brother coming back as his enemy . . . wasn't a pleasant time for Kenzaki.
* DarkIsEvil: So, so very much in Sauron's case.
* DemonicPossession: Sauron spent so long bonded with Kat/Neko Hasuma that even separated from them, her default human form looks a lot like an eviler version of them.
* EvilCounterpart: Ryuji started as this to [[MessianicArchetype Ryuki Hasuma]], but slowly gained his own independent will and sentience . . . and positive emotions along with that. Nowadays, he's treated more like a twin brother than anything else.
* EnemyWithout: An odd case, in that the situation is a lot like Captain Kirk's in the original Star Trek series, with Kat and Neko being the distilled negative and positive aspects of each other. Thankfully, Kat is not so much evil as simply very mean-spirited and Neko's not so good that she can't put up a decent fight when properly motivated. Sauron, who once possessed the original gestalt persona of Kat/Neko, could be considered a more-or-less straight example of this trope, as she's based her human appearance on them and is very, very evil.
* EvenEvilHasLovedOnes: Sauron has a wife and queen named Rosalinda, the A/U version of Rose Wilson of the Teen Titans setting, who just happens to be Kat Hasuma's wife. Sauron also has a couple of kids with Rosalinda, and the children and Rosalinda are the only people she can be safely said to love at all.
* EverythingsCuterWithKittens: Neko may well be this trope in human form, at least as contrasted with Kat, who would be more like the human personification of CatsAreMean.
* FeelNoPain: Goes hand-in-hand with the accident that also gave Kenzaki his iron skin.
* ForTheEvulz: Almost everything Sauron does is for the sake of spreading evil and misery. As TheHeartless, that's pretty much her entire purpose, anyway.
* {{Forgiveness}}: Ryuji finds it very hard to forgive people who cause pain to his few loved ones. Luckily for them, Kotonoha isn't nearly so hard to convince, and she's the main reason he hasn't butchered everyone who ever hurt her. Also, Kat has a very difficult time forgiving Ken for trying to kill Neko on their first meeting or for "letting" her get raped by his Red Lantern Ring-maddened rival. Of course, it could be argued that what Kat really doesn't forgive Ken for is taking Neko away from her, with everything else largely being a hollow justification for her otherwise unreasoning animosity for him.
* FriendVersusLover: Try "Sister Versus Lover," and you've pretty much got Neko's dilemma in a nutshell. Ultimately, Neko chooses Kenzaki, but only because Kat's gone too far by then for Neko to want anything to do with her for the time being.
* GreenEyedMonster: Kotonoha's a nice girl, she's also pretty and rich . . . and that's more than enough to provoke envy within her tormentors, at least before Ryuji came.
* HappilyFailedSuicide: Considering that Kotonoha ended up with someone who treats her a lot better than Makoto did, even if his default attitude toward anyone else is more along the lines of "aloof punk," Kotonoha is definitely happy that she didn't succeed in killing herself.
* HappilyMarried: Kenzaki with Neko Hasuma.
** [[spoiler: At the end of the series: Ryuji with Kotonoha, Ryuushin with Princess Siera, and Yuji with Princess Rina]]
* HeroicComedicSociopath: Kat in a nutshell; she's on the heroes' side for the most part, barring personality clashes with one or two of them, but she's also incredibly vicious, possesses no sense of restraint when it comes to people who've wronged her, and loves skinship a little too much for her own good . . . and it's all played for laughs, for the most part.
* HiddenHeartOfGold: Ryuji doesn't like letting people see his softer, gentler side.
* HumanoidAbomination: Sauron often looks like your everyday human girl . . . and has quite the body, too . . . if you can look past the creepy hockey mask. But she is the farthest thing from human possible.
* HumansAreBastards: Ryuji believes this. Maybe not as intensely as he used to, but he still believes it to an extent . . . and the world doesn't necessarily prove him wrong.
* IAmAMonster: Ryuji struggles with this a lot due to his origins.
* IfYouEverDoAnythingToHurtHer: Kenzaki gets this a lot from Kat Hasuma, Neko's twin sister. Considering they didn't meet under the best circumstances [Understatement], it's understandable, but Kat's a "Knight Templar Big Sister" who thinks Kenzaki's not good enough for Neko.
* IfYouKillHimYouWillBeJustLikeHim: In a literal sense, this applies to Ken's violent avenging of Neko's rape; the Red Lantern Ring felt his wrath and decided he'd be a more suitable bearer than its last one.
* IneffectualLoner: Ryuji's quite the badass, but when he starts admitting that he cares a lot more about the people in his life than he'd like to let on, his badassery really kicks up a few notches.
* IntimatePsychotherapy: Remember the incident described in "Rape As Drama"? Kenzaki and Neko made love afterwards as a means of psychological cleansing. Some people will likely complain about that, but then, everyone has different ways of coping with things like that, and reality itself can be terribly unrealistic.
* KickTheSonOfABitch: Sauron might be an irrevocably twisted and monstrous demon, but don't tell me you weren't cheering at least a little when she killed those girl-enslaving bastards in that Shitsurakuen one-shot.
* KickTheDog: Kat does this a lot. See WhatTheHellHero? below. Not only she goes too far with trying to break Kenzaki and Neko up(Granted, those two didn't meet under the best circumstances, but they have shown to be over it already), which ultimately leads to Neko leaving with Kenzaki after basically getting fed up with Kat seemingly putting her dislike of Kenzaki over Neko's happiness, but also when, later in the story, she uses Kotonoha to blackmail the Computer Club into giving her a good computer by forcing themselves on Kotonoha in the same way [[LightNovel/HaruhiSuzumiya Haruhi did with Mikuru]].
* KnightTemplar [[BigBrother Big Sister]]: This is Kat's attitude toward Neko in a nutshell, especially when it comes to her boyfriend/husband and erstwhile opponent Kenzaki. Somewhat deconstructed in that many of their shared allies think she's going a little too far, and Neko eventually has enough and takes off with Kenzaki, leaving Kat behind.
* LonersAreFreaks: Actually, Ryuji's a "freak" for reasons other than being a loner, but that doesn't stop people from assuming he's some kind of "troubled youth" because of his loner tendencies. Troubled he may be, but it's for a lot more important reasons.
* LovableSexManiac: Kat.
* LoveRedeems: It was Ryuji's feelings for Kotonoha that got him to start thinking that maybe humans weren't all so bad and that it might be worth it to protect them. Also, Ryuji's love saved Kotonoha from turning into a very psychotic example of "Woman Scorned." Makoto and Sekai should thank their lucky stars.
* MadeOfEvil: Yeah this is pretty much Sauron in a nutshell.
* MadeOfIron: Technically, whatever Kenzaki's skin is coated in is a lot stronger than mere iron. [[spoiler: This applies to his brother too
* MalevolentMaskedMen: Replace "Men" with "Women," and you got it dead right in Sauron's case.
* MartialPacifist: Kotonoha doesn't like fighting, but she's not going to stand helplessly and let Ryuji get himself hurt saving her and everyone else. Thus, she becomes Kamen Rider Tenshi.
* MentorOccupationalHazard: Gou Tsukuba, a.k.a. [[Series/JukenSentaiGekiranger GekiViolet]] and (maybe) the original Kamen Rider Garoh.
* MoralityChain: Kotonoha is this for Ryuji, in that she's the only reason he hasn't killed everyone who tormented and betrayed her . . . and most of his more heroic character wouldn't have shone through if not for her love for him and vice versa. Neko and Rose Wilson of the Teen Titans for Kat; without them, she'd certainly be a lot worse than she is right now.
* MoralityPet: Kat and Rose's daughter Cathy.
* MultiformBalance:
** '''[[color:darkblue:Ryuji Hasuma]]'''/Kamen Rider [[color:darkblue:I]][[color:black:f]][[color:palegoldenrod:r]][[color:red:i]][[color:lightblue:t]]
*** JackOfAllStats: [[color:darkblue:Ifrit]] Form and Sabre Form
*** FragileSpeedster: [[color:palegoldenrod:Tyranno]] Form
*** MightyGlacier: [[color:red:Loki]] Form and [[color:darkred:Mammoth]] Form
*** StoneWall: [[color:lightblue:Tricera]] Form
*** LightningBruiser: [[color:black:D]][[color:palegoldenrod:y]][[color:darkred:n]][[color:lightblue:o]] Form
*** GoldenSuperMode: [[color:gold:Gold]] Form
** '''[[color:silver:Kenzaki]]''' '''[[color:darkviolet:Tsukuba]]'''/Kamen Rider [[color:black:G]][[color:palegoldenrod:a]][[color:gold:r]][[color:darkred:o]][[color:silver:h]]
*** JackOfAllStats: Hunter Form
*** MightyGlacier: [[color:palegoldenrod:Predator]] Form
*** StoneWall: [[color:gold:Rampage]] Form
*** GlassCannon: [[color:darkred:Savage]] Form
*** LightningBruiser: [[color:black:Em]][[color:palegoldenrod:pe]][[color:gold:r]][[color:darkred:or]] Form
*** SuperMode: [[color:silver:Lunar]] Form
* NobleDemon: Ryuji sees himself as a monster and treats being a Kamen Rider as just another job for which he gets a paycheck. Never mind that he saves the world on a regular basis. Never mind that he's a lot more inclined toward protecting said world than he would like most people to believe. Never mind that any objective person can see that he's not nearly as ruthless and coldblooded as he likes to believe he is . . . Of course, if you catch him during one of those soft moments, he'll be very quick to remind those in the know that he's only doing it for Kotonoha's sake and could care less about anyone else. Yeah, sure.
* ObnoxiousInLaws: Kat and Kenzaki towards each other.
* OmnicidalManiac: Sauron is just as fine with outright wiping out entire worlds as she is conquering them.
* PantheraAwesome: Kat in both her Rider form and her Rinki Gaiso form.
* PolarOppositeTwins: Neko tends to be rather demure and extremely sensitive to others' feelings and opinions most of the time, while Kat is extremely boisterous and could care less what anyone else thinks unless it's someone she deeply cares about.
* RapeAsDrama: In the "Grand Finale" arc of Kamen Rider Days, Zodiac Knight Axe rapes Neko simply to strike back at Kenzaki, who reacts very understandably badly to such a thing.
* RedOniBlueOni: With his Imagin partner Loki and with his "twin brother" and template Ryuki Hasuma. Somewhat odd example in both cases because Ryuji is very hotheaded and Ryuki, although an actual redhead, is the far calmer and more peaceable of the two. Loki is also far friendlier than the ever-combative Ryuji, which might be a somewhat straighter example of this trope in action.
* ReformedButRejected: Makoto's trying his best to be a better man, but it's gonna be a cold day in hell before Ryuji is ready to forgive him for his actions concerning Kotonoha.
* RescueRomance: Kotonoha started to fall in love with Ryuji when he saved her from committing suicide after finding out about Makoto and Sekai, and then from almost being raped by Taisuke Sawanaga.
* RoaringRampageOfRevenge: Kenzaki does this a few times in the course of the story, especially after his rival becomes Zodiac Knight Axe and does the unforgivable to Neko.
* SecondLove: Ryuji is Kotonoha's second love, and a truer love one could never find.
* SiblingTeam: Kat and Neko on their own, and also with their brothers Ryuki and Ryuji Hasuma, whose shared existence is owed to a similar "Enemy Without" situation.
* StarCrossedLovers: Neko and Kenzaki, at least insofar as Kat's determined to break them up and goes to some pretty unacceptable lengths to achieve that goal.
* SuperpowerLottery: Warren. Big time. So far, he is: half-angel, a kamen rider, [[{{Manga/Bleach}} A vizard, Tosen's replacement as the 9 squad's captain in the Gotei 13]] and [[KingdomHearts a keyblade wielder]]. Have we missed anything?
* SupernaturalMartialArts: Kenzaki inherited his fighting skills from the late, great Gou Tsukuba.
* SuperpoweredEvilSide: His Orphenoch form, at least when he loses control of it, could be considered this.
* TheCorrupter: Sauron loves doing this, either by her own clever manipulations or by way of "The Corruption."
* TheHeartless: Sauron leads the Horrors, demonic spirits that feed off negative human emotions and impulses and use them to infect and warp humans into physically and mentally twisted monstrosities.
* TheSoulless: The "malevolent psychopath" kind of soulless, that is. Sauron might have a soul, but it's probably so twisted and degenerate that she might as well not have one.
* TokenEvilTeammate: Kat is a somewhat extreme case of "Chaotic Neutral" rather than outright evil, but like the trope description says, "evil" in this case is not beyond the concepts of friendship and loyalty . . . even if they are stretched rather thin when it comes to how much Kat dislikes Kenzaki.
* TomboyAndGirlyGirl: Kotonoha has this relationship with her Imagin partner Athena, with Athena as the "Tomboy" and Kotonoha as the "Girly Girl." This also applies to Kat and Neko, and you get no points for guessing which is which.
* TookALevelInBadass: Kotonoha!Kotonoha![[RuleOfThree Kotonoha!]]
* TroubledButCute: As far as Kotonoha is concerned, yes.
* {{Twincest}}: A one-sided version of this is suspected by some people when it comes to just how far Kat takes her "Big Sister Instinct" for Neko.
* UltimateEvil: In a nutshell, this is what Sauron is.
* ViolentlyProtectiveGirlfriend: Kotonoha is very much so when it comes to Ryuji. If he doesn't kick your @$$, she will.
* VitriolicBestBuds: Ryuji is this with Kenzaki Tsukuba, a.k.a. Kamen Rider Garoh and the lover (later husband) of Ryuji's sister Neko Hasuma.
* WhatDoesSheSeeInHim?: Many of Kotonoha's classmates asked this when she and Ryuji became more openly involved with each other. Ryuji occasionally wonders this himself, only to be reassured every time.
* WhatTheHellHero?: Several people give this to Kat when it comes to her antics, especially her trying to break up Neko and Kenzaki, but Neko gives the coup de grace of this trope by outright leaving with Kenzaki, unable to bear her sister's refusal to let Neko's happiness outweigh her personal distaste for Kenzaki.
* {{Xenafication}}: In a sense, compared to Kotonoha's original incarnation in "School Days."
* {{Yandere}}: Averted with Kotonoha thanks to Ryuji's intervention, but shades of this persist in her personality, particularly when Ryuji is hurt especially badly by a foe.
* YouAreNotAlone: Having this explicitly demonstrated by Ryuji when he saved Kotonoha from killing herself.