----

* ''Fanfic/ACrownOfStars'': Avalon's army commanders Ching and Bir. Ching is the Red Oni -enthusiastic, mirthful and passionate- and he is the Blue Oni -calm, serious and somewhat staid-. They are also a BattleCouple.
* ''Fanfic/AdviceAndTrust'': Asuka and Rei. The differences between them become less extreme after Rei stops taking emotion-suppressor meds, but Asuka is still hot-blooded and impetuous and Rei is still quiet and calm. During the story their friendship develops and they become a very close-knit combat unit together with Shinji.
* Story/AesirCrossWars: Inverted. Freya is the staff wielding, intelligent goddess of Love, while her Guardian, Azrael, is the scythe wielding angel with IdiotHero tendencies. In spite of this, it is Azrael who comes off as the calmer of the two, often correcting his Goddess whenever she makes a mistake. Meanwhile, Freya is a massive GenkiGirl.
** Played straight with Azazel and Azrael respectively. Azazel is HotBlooded, a demon, has black hair, is a JerkWithAHeartOfGold, and knows Fire magic. Azrael is calm, an angel, has blond hair, is a NiceGuy (strictly speaking, he's also a JerkWithAHeartOfGold due to his near-constant snarking, but he is ultimately kind and definitely comes off as more tolerant than Azazel) and knows Lightning magic.
* ''Fanfic/ATriangleInTheStars'': While Steven is undoubtedly the Red Oni to mostly everyone else, he's the Blue Oni to Bill Cipher's Red. [[spoiler: Later, however, Bill evolves into more of a Blue Oni, and Steven himself bounces back and forth from Red to Blue.]]
** While usually the Blue Oni in the show, Connie is actually the Red to [[spoiler: Wendy's]] Blue. Though they very rarely switch roles.
** Stanley Pines is the Red to Stanford Pines's Blue, and [[spoiler: Peridot]] is the Blue, and sometimes Red, to both of them.
** Garnet is the Blue to Pearl's and Amethyst's Red, and Pearl is the Blue to Amethyst's Red. [[spoiler: When Keyhole joins, he becomes the Blue to Pearl's Red]].
** [[spoiler: Gabriel]] is and has always been the Red to Bill Cipher's Blue.
** And finally, [[spoiler: Jasper]] is the Red to [[Lapis's]] Blue. It helps that they're actually a version of red and of blue respectively.
* ''Fanfic/BloodAndHonor'': Vette - talkative, excitable, more at home in the underworld than anywhere else, wielding dual blasters and spending most of her free time in cantinas - versus Quinn - traditional, reserved, dedicated to the Empire and his duty, a consummate professional who looks down his nose at those he thinks are unprincipled or undisciplined.
* ''Fanfic/TheChildOfLove'': Asuka is the Red Oni and Rei the Blue Oni. Shinji compares them in the first chapter, saying Asuka is fierce and loud whereas Rei is calm and quiet.
* ''Fanfic/ChildOfTheStorm'': Harry and Carol alternate between the two roles. On the one hand, Harry's the one with emotional repression issues, NervesOfSteel, a habit of very dry [[DeadpanSnarker snarking]], and when he gets ''really'' angry, the result is TranquilFury. Carol, meanwhile, is a loud, HotBlooded teenager with anger issues and a bit of impetuosity. On the other hand, Harry's also increasingly got a HairTriggerTemper which he struggles to keep in check, is practically the poster boy for the IndyPloy and DidntThinkThisThrough and his signature power is PlayingWithFire. Meanwhile, Carol is reserved, cautious about trusting people, Harry's self-appointed MoralityChain who never loses control of herself, functions as TheStrategist for Harry and his friends, and has an increasingly disciplined mind, sufficient to [[spoiler: earn the right to wield the Green Lantern Ring]].
** Steve is the Red Oni to Bucky's Blue Oni, with the former being more emotional and explicitly more connected to his humanity, while the latter is/used to be the Winter Soldier, and retains a cold, ruthless and intensely pragmatic streak, as well as tending to be quiet, thoughtful and patient, while Steve - though not lacking caution or pragmatism himself, will always stride straight into battle as soon as required.
** Thor and Loki, of course. Thor's the Red Oni, Loki's the Blue Oni.
** Jean Grey and [[spoiler: Maddie Pryor/Rachel Grey]]. Jean is sweet, lovely, an absolute sweetheart who's open with her emotions... and possessed of a spectacular and terrifying temper. [[spoiler: Maddie/Rachel]], by contrast, is almost entirely calm, practical, logical, reserved, and capable of being very, very cold - though post HeelFaceTurn, the facade cracks somewhat.
* ''Fanfic/ChildrenOfAnElderGod'': Asuka is the Red Oni -being fiery, high-spirited and loud- and Rei the Blue Oni -she is quieter, colder and usually emotionless-. As a bonus, Asuka has fire-related powers.
* ''Fanfic/DoingItRightThisTime'': Asuka was the Red Oni -temperamental and impulsive- and Rei the Blue Oni -emotionless and quiet-. After returning to the past Asuka is calmer and Rei is learning to recognize and express her emotions, so differences between both are less extreme, but Asuka is still the passionate half of the duo and Rei the calm one.
* ''FanFic/DungeonKeeperAmi'' features [[NobleDemon Jadite]] and [[BadAssBookworm Ami]], occasionally. Jadeite also fills the same role to [[MissionControl Cathy]]. On the other hand, Tiger is a red oni to everyone, even Jadeite.
* ''Manga/{{Evangelion 303}}'': [[FieryRedhead Asuka]] is the Red Oni -she is hot-tempered, hot-headed, loud, boisterous, proud and impulsive-, and Shinji is the Blue Oni -calm, modest, quiet, patient, wary, understanding-. They are a BattleCouple.
* In ''Fanfic/GhostsOfEvangelion'' Asuka is the Red to Shinji's Blue. She is hot-blooded, quick-tempered and impetuous, and Shinji is calm, rational and passive. She helps him be more assertive and he keeps her calm.
* ''Fanfic/{{HERZ}}'': Asuka is the red oni (she is temperamental, rash and hot-headed) and Rei the blue one (she is calm and soft-spoken). Due to their clashing personalities there was some hostility between them when they were young, but after twelve years it has mostly faded.
* ''Fanfic/HigherLearning'': Asuka and Shinji were this for a long time. They were always together, and Asuka was the hot-headed, enthusiastic Red Oni and Shinji the quiet, meek Blue Oni. This changed after [[spoiler:Asuka's MindRape,]] and she became silent and gloomy.
* ''Fanfic/LastChildOfKrypton'': Passionate and fiery Asuka is the Red Oni while collected and silent Rei is the Blue Oni. It was specially noticeable in scenes where Asuka reacted and acted while Rei prefered waiting and analyzing the situation.
* ''Fanfic/OnceMoreWithFeeling'':
** Asuka and Shinji are like this. Asuka is the Red Oni -temperamental, bold and daring- is the Shinji is the Blue -tranquil and quiet even when he is angry-.
** Rei -calm, soft-spoken- is also the Blue Oni to Asuka's Red one. Due to Shinji changing the timeline events they unexpectedly become friends, and better teammates (and Rei actually [[spoiler:saves Asuka's from dying inside a volcano.]]
* [[https://www.fanfiction.net/s/6218113/1/Professor-Layton-and-the-Beam-Katana-Chronicles Professor Layton and the Beam Katana Chronicles]] pairs the hot headed and rash [[VideoGame/NoMoreHeroes Travis Touchdown]] with the calm gentleman, [[Franchise/ProfessorLayton Hershel Layton.]]
* ''Fanfic/RagnarokRagnaGuardian'':
** Shiro (HotBlooded, sanguine, NiceGuy, loud and extroverted) and Reiko (Choleric, even louder, bossy) as the red to either either Saya (Introverted, ShrinkingViolet, quiet, phlegmatic) or Roku (Melancholic, JerkWithAHeartOfGold)
** Also Shiro and Kuro respectively
** Shiro can only be out-redded by Reiko and his sister, Shiki
* The wrestling fic [[https://www.fanfiction.net/s/10340937/1/The-Return-Remixed The Return-Remixed]] has DEAR's BigBadDuumvirate, Wrestling/TrishStratus and Wrestling/{{Lita}}. Trish is cocky and arrogant when things are going her way, but loud and hot-headed whenever they're not, while Lita is more level-headed and rational.
* ''Fanfic/TheOneILoveIs'': Asuka -HotBlooded, hot-headed, angry, loud- and Rei -emotionless, detached, calm, quiet-. Their relationship greatly evolves throughout the story. At the beginning Asuka detests Rei and Rei ignores Asuka. Later, when they start competing over Shinji, they can not stand each other. Finally, after a violent fight, they make up, call a truce, and they gradually become friends.
* ''Fanfic/SOE2LoneHeirOfKrypton'':
** Asuka was the Red Oni -passionate and temperamental- and Shinji the Blue Oni -meek and quiet-. Actually, Asuka liked Shinji -among other reasons- because he knew how to listen.
** When Asuka and Rei hang together and fight together, Rei -quiet and passive- is the Blue Oni.
* In the Great Chicken Miasma's Mario fanfic ''Fanfic/BetterOffAlone'', the young Yoshi Waffles is the Red to everyone else in the group's Blue.
* In the fanfic [[http://www.fanfiction.net/s/6984913/1/Disgaea-Jewel-of-the-gods Disgaea: Jewel of the Gods]], Laharl is the red oni to Adell and Mao's blue oni. Adell and Mao tend to trade role for who's the red oni and who's the blue oni of the two.
* ''Fanfic/WhatAboutWitchQueen'' has two pairs like this on opposite sides of war. On Arendelle side, general Kristiani is impulsive, "let's crush them now" red to Olafsen's more careful blue. On Weselton side, general Potter is red with MoreDakka approach, while general Windsor is blue and described as "cold-blooded, sneaky bastard" by one of the Arendellans.
* ''FanFic/WinterWar'' gives us Ikkaku and Nanao, the co-leaders of the Hueco Mundo mission. Ikkaku is a HotBlooded BloodKnight with a newly acquired habit of [[TheNicknamer giving nicknames]] and a physical fighter with no aptitude for kidou. Nanao is a [[NoSenseOfHumor serious]], methodical, control obsessive BadassBookworm and kidou specialist who so far has avoided hand-to-hand combat.
* ''[[FanFic/ErisGame Eri's Game]]'' has Eri as the Red Oni and her best friend, Shiki, as the Blue Oni.
* ''Fanfic/Swing123AndGarfieldodiesCalvinverse'' has [[MadScientist Dr.]] [[StupidEvil Brainstorm]] as the red oni, with his {{foil}} [[SnarkyNonhumanSidekick Jack]] being the blue.
** The main cast also has this distinction. From most red to most blue, they are as follows: [[color:#ff0000:Socrates]], [[color:#d5002b:Calvin]], [[color:#aa0055:the MTM]], [[color:#5500aa:Hobbes]], [[color:#2b00d5:Sherman]], and [[color:#0000ff:Andy]].
* ''FanFic/ToKillAThief'' has [[Manga/DeathNote Light Yagami]] as red due to [[AxCrazy being crazy]] with KnightTemplar ideas, while his partner, [[Manga/KamikazeKaitouJeanne Miyako Toudaiji]], is blue due to [[OnlySaneMan being sane]] with ByTheBookCop tendencies.
* In ''Fanfic/WhiteRain'', it is Sasuke who is the Red Oni to Naruto's Blue, strangely enough. Their relationships also have the same distinction.
* ''Fanfic/TheWizardInTheShadows'' has Harry as the Red Oni to Aragorn's blue.
* ''FanFic/{{Apprentice}}'' has [[{{Manga/Naruto}} Sasuke]] and [[ComicBook/ArchieComicsSonicTheHedgehog Mecha Sally]].
* ''Fanfic/ChildrenOfTime'' has [[WesternAnimation/SherlockHolmesInTheTwentySecondCentury Beth's]] red to [[Literature/SherlockHolmes Holmes's]] blue.
* The dynamic between [[spoiler: Chaos]] and Takato in the ''FanFic/TamersForeverSeries'' is an interesting inversion of this trope. [[spoiler: [=ChaosGallantmon=]]] has blue highlights on his armour, while Gallantmon has red highlights, and [[spoiler: Chaos]] is also much more ruthless than Takato, but surprisingly enough, ''Takato'' is actually the Blue Oni, being much more subtle and thoughtful than the impulsive [[spoiler: Chaos]].
* ''FanFic/WorkingTogether'' has [[Anime/DigimonTamers Rika Nonaka]] as the Red Oni and ArchEnemy [[WesternAnimation/JackieChanAdventures Valmont]] as the Blue Oni.
* Vale Whitaker, the ShrinkingViolet heroine of the HungerGames fanfiction ''Fanfic/SomeSemblanceOfMeaning'', is the Blue Oni in contrast to several Red Oni in the story, including [[HotBlooded her sister Maybelle]], [[KidSidekick her district partner]] [[MouthyKid Kit]], and FieryRedhead [[ArcherArchetype Fen]].
* ''Fanfic/KitsuneNoKenFistOfTheFox'' gives us Suigetsu and Jugo, red and blue respectively. Suigetsu is HotBlooded, while Jugo's more calm and methodical.
* The ''Manga/MedakaBox'' fanfic ''Fanfic/WorldAsMyth'' has the friendship between the violent [[AxeCrazy Unzen]] and the phlegmatic [[TheStoic Choujabaru]].
* ''Fanfic/ANecromancersWildCard'' has [[LightNovel/{{Is This A Zombie}} Ayumu Aikawa]] as the Red Oni to [[VideoGame/{{Persona 3}} Minato Arisato]]'s blue.
* ''Fanfic/PeaceForgedInFire'' plays this contrast between ''Rahaen'Enriov'' D'trel ir'Aehallhah t'Rihannsu and ''Khre'Riov'' Morgaiah "Morgan" ir'Sheratan t'Thavrau, the two lead members of the Romulan Republic diplomatic team. D'trel doesn't like Velal, the Praetor of the Romulan Star Empire, and has diametrically opposed political views, and runs on UnstoppableRage in battle, while Morgan is a more traditionalist Romulan, shares a friendly drink with Velal to hold the negotiations together, and has a much calmer, more rational fighting style. Also visible in their ship choices: D'trel's ''Kholhr'' is a GlassCannon[=/=]FragileSpeedster ''T'varo''-class light warbird, while Morgan captains a MightyGlacier ''D'deridex''-class battlecruiser.
* In contrast to the source material, in {{Fanfic/Traveler}}, Ash is ''blue'' to Gary's red. He serves a similar role to his early travelling companion Jonathan. Lance and Steven's relationship has tones of this, with Lance as red and Steven as blue.
** Appropriately, among Ash's Pokemon, [[PlayingWithFire Infernus]] plays the red to [[MakingASplash Torrent's]] (post-evolution) blue.
* ''Fanfic/TheSnowHasStoppedTheRain'' has Zangetsu, who's crude, violent and hot-blooded (red) and Shirayuki who is (usually) calm, collected and proper (blue).
* ''Fanfic/{{Wonderful}}'' has Taylor, who is the Red to Emma’s Blue. The former is bold and loud whereas the latter is calm and rational. Emma often helps to keep Taylor grounded.
* In ''Fanfic/ThousandShinji'':
** Asuka is the red oni and Rei the blue one. Reinforced because Asuka's powers are fueled by fury and fierceness, and Rei's by joy and despair.
** Shinji is also the blue to Asuka's red. She is a furious, passionate physical fighter. He is a calm, conniving schemer.
* In ''Fanfic/TheSecondTry'', Asuka is the Red Oni to Shinji's Blue. Although she's calmer and he's less timid due to their increased maturity, she's still daring, bold and passionate whereas he tries to be a calming, pacifying influence.
* ''Fanfic/NeonGenesisEvangelionGenocide'': Asuka is the Red to Shinji’s Blue. She’s belligerent, passionate and rash. He’s calm, insecure and quiet.
* The crossover [[https://www.fanfiction.net/s/12068240/1/Crossfire Crossfire]] has [[Anime/{{Trigun}} Vash]] and [[Anime/{{Gungrave}} Brandon]] as the Red and the Blue respectively. Vash is a loud, cheerful donut-loving goofball who always tries to resolve every conflict peacefully. His favorite flower is red geranium, and when he somehow gets in a fight, he will always find a way out with various tricks. On the other hand, Brandon is a cool and quiet undead mobster who won't hesitate to injure or even kill people when it's necessary to resolve a conflict. His favorite flower is forget-me-not, and whenever he gets in a fight, he tends to bulldoze everything in his path with brute strength.
* In ''FanFic/CardcaptorRad'', there's eager and passionate Hot Shot whose something od a BloodKnight, and calm, meticulous Red Alert, who'd rather wait and plan things out. Unsurprisingly they clash a lot.
* In ''FanFic/BladeDanceAcademy'', we have Yona and Tegami, respectively. Yona is a GenkiGirl, NiceGirl, uses [[PlayingWithFire fire]], and wields a BFS. Tegami is a MellowFellow, JerkWithAHeartOfGold, uses [[BlowYouAway wind]], and wields a katana. Their eye colours and CharacterAlignment aren't a clear indicator of this, however, as Yona is a LawfulGood character with blue eyes, and Tegami is a ChaoticGood character with pink eyes.
* In ''Story/InfiniteGateOfHope'', we have our two male leads. Shura is HotBlooded, ChaoticGood, a JerkWithAHeartOfGold, is coded with red and wields [[AnAxeToGrind an axe]], seemingly embodying Thor. Naito is a MellowFellow, LawfulGood, a NiceGuy, is coded with light blue, and wields twin shortswords. Even so, he doesn't rely on them, preferring to use the extremely powerful magic at his disposal.
** Their stat distributions fit this too. Shura is a MightyGlacier, with heavy emphasis on Attack and Vitality. Naito is more of a SquishyWizard, with more focus on Magic and Speed.

* ''Fanfic/SkyBladeAcademy'': [[PlayingWithFire Fire-using]] {{Keet}} Kaiba and HotBlooded [[BlowYouAway Wind-using]] Shiki as the Red, and TheStoic [[MakingASplash Water-wielding]] Atsuya and [[DishingOutDirt Earth-using]] ExtremeDoormat with {{Troll}} tendencies Samekou as the Blue. On the FourTemperamentEnsemble, they are respectively Sanguine (Kaiba), Choleric (Shiki), Melancholic (Atsuya), and Phlegmatic (Same).
----