There are clues a creator can apply to a pair of characters to indicate that that they are opposites in some way. One of those is to give the characters opposite handedness, making them more than just metaphorically mirror images.
Expect to see tropes like Evil Counterpart, Evil Knockoff, Cain and Abel, Polar Opposite Twins, The Lancer, or The Rival and Rival Turned Evil. Also expect to see a lot of parallels in their respective characters and stories - they are as much alike as they are opposites. Commonly, they will represent what the other could have become, had they made different choices or had slightly different luck.
Note that in Real Life, 20% of twins (including identical twins) have opposite handedness, which may be part of the origins of this trope.
Most often, the character with the left hand will be the evil one, or at least less of a hero than the right-handed character.
Compare Hair-Contrast Duo, where another physical characteristic is used to symbolize the contrast between characters.
- Lyrical Nanoha:
- Fate Testarossa from Magical Girl Lyrical Nanoha is this on two levels: firstly, she is a right-handed Dark Magical Girl to the left-handed title character. Secondly, she is an imperfect clone of her creator's late left-handed daughter; in fact, Fate's handedness was one of the things that made Presea realize that she is not Alicia and reject her.
- In Magical Girl Lyrical Nanoha Strikers, Subaru Nakajima and her left-handed older sister, Ginga, have each one of the two Revolver Knuckles from their late mother, Quint. Additionally, a Revolver Knuckle can change its color to fit the color scheme of the holder, resulting that Subaru's right Revolver Knuckle is black while Ginga's left Revolver Knuckle is white.
- Rosario + Vampire has a variation in Hokuto Kaneshiro, acting as a sort of mirror to main character Tsukune Aono. Both are humans come to this school for monsters by sheer luck (or lack thereof; neither is really sure), both are given monster blood to survive, and both end up with out-of-control monstrous powers. Tsukune Aono's monster blood is sealed by a Holy Lock on the wrist of his right hand, and he has an honest determination to make alliances between humans and monsters. Hokuto Kaneshiro's mosnter blood is sealed by a Holy Lock on the wrist of his left hand, and he goes absolutely monstrel-shit crazy and tries to send monsters and humans into an utter and complete bloodfest.
- In Yu-Gi-Oh! 5D's, Z-One acts as one for Yusei. Z-One is left-handed and even modified his body to look like Yusei. He once had the same idolism as Yusei, but due to him coming from a Bad Future, his dreams has been crushed and his vision changed drastically, so he sees as destroying the past to prevent the Bad Future from happening as his last option, while Yusei has still hope that the future can be saved.
- The brothers Higake and Tsukikage from Yu-Gi-Oh! ARC-V. Hikage is right-handed, has a red costume and uses an offensive strategy, while his younger brother Tsukikage is left-handed, has a blue costume and uses a defensive strategy.
- Stocking in Panty & Stocking with Garterbelt is shown to be left-handed, in a way making her the left-handed mirror to her (opposite in personality) older sister, Panty.
- In Tokyo Ghoul, Ken Kaneki and Eto/Sen Takatsuki, the One-Eyed Owl. Both are Half-Human Hybrids, and their similarities are even pointed out by the Owl during an encounter between them. Kaneki is right-handed with a left kakugan, while the Owl is left-handed with a right kakugan.
- Bleach: Ichigo and Uryuu are designed to be opposites of each other. Ichigo's battle uniform is Japanese clothing, black on white. Uryuu's clothing is European, white on black. Ichigo fights close up with a sword, Uryuu fights at a distance with archery. Ichigo is impulsive in battle and fights on instinct while Uryuu is a thinker and a strategist in battle. Ichigo's powers are Shinigami-dominant and Uryuu is a Quincy. The Quincies and Shinigami are mirror opposites of each other, even their souls are aligned as opposites, and the two sides have been at war for a thousand years. Kubo has stated in interviews that Uryuu is left-handed to complete the mirroring of Ichigo, and characters have observed in-universe that the pair are Not So Different due to their mirrored personalities and abilities complementing each other perfectly.
- The Nancy Makuhari clones in Read or Die are mirrored, and in the climax of the OVA face off against each other. It's not clear which Nancy survived the fight until she kills the Big Bad with a fist phased through the heart. She then off-handedly comments that she switched her gun to her non-dominant hand to throw everyone's attention. Inverts A Sinister Clue, too; the "good" Nancy is The Southpaw.
- Quite Literally in "Let's Get Invisible!" from Goosebumps. Lefty's counterpart in the mirror world is right-handed and he switches places permanently with Lefty.
- The Reynard Cycle: Reynard and Isengrim's Red Oni, Blue Oni relationship with each other evokes this trope in the names of their weapons: Isengrim's sword is called Right-Hand, while Reynard's Blade Below the Shoulder is called Left-Hand.
- Arya and Sansa Stark of A Song of Ice and Fire. The Southpaw Arya is a Tomboy and a Deconstruction of the Rebellious Princess archetype, while her right-handed sister Sansa is the girly-girl and a Deconstruction of Princess Classic.
- In James Blish's Spock Must Die!, a duplicate of Spock is left-handed. He has to fake right-handedness to maintain his cover.
- Played with in The Prisoner (1967) episode "The Schizoid Man". Number 2 creates an exact double of Number Six and uses him to confuse Number Six into thinking that he's the double. The Villagers use aversion therapy on Number Six to turn him from right-handed to left-handed (while on drugs so he won't remember it). The double is right handed, which he uses to claim that he's the real Number Six. If falls apart when Six notices a clue of how much time has really passed, causing him to remember the aversion therapy.
- In Orphan Black, Helena, the only left-handed clone, is a serial killer brainwashed into thinking she's the original. The "mirror" part comes into play when we learn that she's Sarah's twin.
- Vocaloid brings this out with Len and Rin Kagamine, opposite-gender mirrors of each other or Half-Identical Twins (depending on who you ask). Their genderswaps even look a lot similar to the twin. This trope is most evident in Fanon works involving these two, as their official characterizations are virtually nonexistent.
- An Iroquois legend states that the world was created by a pair of twins. The right-handed twin made the landscapes, plants, and animals. The left-handed twin created snakes, thorns, and storms.
- Angelo in Dragon Quest VIII is a lefty, and a smarmy, hedonistic womanizer who shirks from his templar duties. His half-brother Marcello is right-handed, stone-faced, and deadly serious about his templar duties.
- Fire Emblem: Shadows of Valentia uses this trope to show how its protagonists are two halves of a whole rather than in any kind of opposition. Lefty Alm and right-handed Celica have plenty of Foil-ish traits, from their fighting styles and peacemaking methods to the hands that bear their Birthmark of Destiny, and overall, Alm is more roguish-heroic than the noble, pacifistic Celica. Then it's revealed that Celica is the hidden princess of the protagonistic nation Zofia, and is The Chosen One of its goddess, while Alm is long-lost prince of Rigel, the very kingdom he was fighting against, and was himself chosen by Rigel's own, harsher god, and they're each the last living members of their royal bloodline. That said, neither is truly more heroic than the other, and they're both destined to unite the two kingdoms anyway, but in a twist, when comes to the Big Bad, Celica is the one he possesses to kill Alm, and Alm is the one who is chosen by the only sword that can kill him. note
- Luciana and Aegiana of Yggdra Union who, despite being identical twins, have opposite handedness. Red Oni, Blue Oni is in full effect for these two.
- The Final Fantasy series is quite fond of this trope:
- Final Fantasy II: Leon, a guest member during the first unbeatable fight who later found to be brainwashed and working for The Empire as a dark knight, is left-handed, in contrary with his best friend Frion, The right-handed hero with a overall theme of being a warrior of light.
- Final Fantasy IV:
- Kain, who is in many ways a "what could have been" for right-handed hero Cecil. Both share a very similar backstory, and both vow to fight against Baron, but Kain ends up Brainwashed and Crazy and fighting for Golbez, while Cecil narrowly avoids that fate and becomes a Paladin.
- Cecil's unknown brother Golbez from the same game is left-handed, and only through luck did Cecil not end up in Golbez's villainous role.
- Twins Palom and Porom, who are Polar Opposite Twins in both personality and powers, with one being a Black Magician Boy and the other being a White Magician Girl. Palom is the left-handed twin, and far less nice than Porom, although he is by no means a villain.
- Similarly, in Final Fantasy VII and Crisis Core, Sephiroth is left-handed while both Cloud and Zack are right-handed. They are in many, many ways warped mirror images of each other.
- In Final Fantasy Dimensions, Nacht and Sol are both orphans chosen by the Crystal. Right-handed Sol is the leader of the Warriors of the Light, and is an Idiot Hero Genki Boy, with blond hair, and a name that means sun. Left-handed Nacht is the leader of the Warriors of the Dark (although Dark Is Not Evil in this game), and is The Stoic, with dark teal hair, and a name that means night.
- An interesting variation occurs in the Kingdom Hearts series. Protagonists Terra and Riku have many, many parallels, including sharing the same role in a Two Guys and a Girl trio, complete with same Theme Naming. They both are destined keyblade wielders, both are misled and manipulated by Maleficent and Xehanort, and both succumb to the Darkness in their hearts. But while Terra is lost to his inner Darkness and becomes a Xehanort host, Riku conquers his inner Darkness and uses it to defend the Light, thus escaping Terra's fate. The variation occurs in that both characters are actually right-handed, but nearly all Terra's powers of Darkness manifest through his left hand, while Riku's manifest through his right.
- In Tales of the Abyss, Asch wields his sword with his right arm and Luke wields his with his left. In a twist, however, Luke is the Left-Handed Mirror to Asch rather than the other way around. In another twist, Asch is actually also left-handed - he just taught himself to fight right-handed to differentiate himself from Luke, whom he despises.
- Similarly, in Tales of Vesperia Yuri wields left-handed by default (though he can and does occasionally switch to his right), while Flynn is right-handed. Fittingly, Yuri is much more of an Anti-Hero than Flynn is, and has a more creative combat style. Vesperia also gives us twin assassins Gauche and Droite, whose names literally mean 'left' and 'right' in French.
- Happens logically in Glover, where the protagonist is an enchanted magician's glove. The bad guy, naturally, is the other glove.
- A prime example is the original The Legend of Zelda games. A bit twisted around though because Link is the left-handed hero and Ganondorf is the right-handed villain.
- Inverted in a rather literal sense in the earlier 2D games, and in Wii games, where Link is right-handed when facing west, or where his dominant hand needs to match the majority of players. In the case of Twilight Princess, the entire game was mirror-inverted in the Wii version compared to the GameCube version. However, as of Breath of the Wild on Wii U and Nintendo Switch, motion control is no longer the reason for Link being right-handed.
- Siegfried Schtauffen and his Superpowered Evil Side, Nightmare, from the Soul Series are ambidextrous. While Siegfried prefers to wield his sword in his right hand, Nightmare prefers to wield it in his left hand.
- Shadow the Hedgehog is left-handed in his own game, possibly to invoke this trope to oppose him to Sonic, who is right-handed.