* ''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 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, [[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).
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