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* ''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 both 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.
* ''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 one. Shinji compares them in the first chapter, saying Asuka is fierce and loud whereas Rei is calm and quiet.
* ''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.
* ''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 and 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, Professor 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, Shima
* ''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 can also, arguably, qualify as the red oni to Mao's blue oni.
* ''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.

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