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Fanfic / Kazuma V Tanya

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A three-way crossover, Kazuma V Tanya tells the story of two isekai protagonists reborn (again!) into another world.

Kazuma of KonoSuba finds himself reborn in the world of Mistborn: The Original Trilogy as Reen, older brother to the series protagonist Vin, and he quickly becomes a Masked Chivalrous Thief to support his sister and get some payback on the corrupt nobility. Meanwhile, the protagonist of Saga of Tanya the Evil finds herself sent to another world again by Truck-kun, reborn as Taniar "Tanya" Tekiel, a low-ranking child in a noble house. Her status quickly rises after she is discovered to be a Mistborn, and with her adult mind Tanya quickly begins leveraging her status and abilities into getting as many meat-shields as possible between her and the other Mistborn who will want to kill her for their Noble Houses.


Naturally, these two clash both before and throughout the events of the Mistborn series, as Kazuma goes for grander and grander acts of larceny while Tanya maneuvers her way into forming a strike team aimed at stopping him.

One thing's for sure...with these two interfering with the trilogy, there's bound to be a magnificent Gambit Pileup at some point!


  • Anachronic Order: The chapters alternate between Tanya's and Kazuma's POV, beginning with Tanya's birth and childhood, with the next chapter showing Kazuma's birth and childhood, and so on, even though Kazuma is the physically older of the two.
  • Big Brother Instinct: Kazuma to Vin. Try to hurt Kazuma and he'll beat both you and the entire criminal organization you work for into the ground but will still be willing to buy everyone a beer later if they agree to let bygones be bygones. Threaten Vin, however, and he'll vaporize your skull mid-sentence before massacring the rest of your associates with lightning and a loaf of bread.
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  • Bond One-Liner: Kazuma gives a particularly...fitting one after massacring the Big-Mouth girl's group.
  • Born Lucky: Kazuma still relies heavily on his Luck Stat to pull crazy stunts. (Also, he got to keep his Adventurer Skills in his new life, while Tanya lost her former magic.)
  • Bullying a Dragon: The muggers and thieves who decided to ambush Kazuma in Chapter K03 really should have known better considering how absolutely outclassed they were in all their previous encounters. They don't live to repeat their mistake.
  • Catchphrase: Tanya's "Curse you, Being X!"
  • Combat Pragmatist: Both Tanya and Kazuma, accounting for their differing skill sets.
    • Tanya wears a helmet, aims for the head, heavily uses pewter to enhance her young body, and has subordinates positioned to support her in combat whenever possible.
    • Kazuma dodges a lot and lures people in before using prepared items to augment his Adventurer Skills.
  • Create Your Own Hero:
    • While Kazuma was always unsatisfied with his new life in Scadrial, he didn't have any intention of opposing the nobility until a Tekiel noble heard him complain and sent his guards to kill him. Kazuma was able to easily give them the slip and escape to a rooftop...only to watch the guards grab another child that looked only vaguely like Kazuma and slit their throat. After paying his Due to the Dead, he hunts down the noble's house to pilfer as much as he can before setting the whole thing ablaze. He's continued his vendetta against House Tekiel for years.
    • Aqua is entirely convinced that, by having Kazuma's little sister killed, Ruin has effectively sealed its own doom by inciting the wrath of the Billionaire Adventurer.
  • Darker and Edgier: Kazuma learns that his new life is this when his loud complaining prompts a passing noble to kill him; Kazuma successfully escapes, but then sees another kid get killed instead, with no one trying to stop it or even caring to.
  • Declaration of Protection: Kazuma gives one to both his little sisters after they're born and does absolutely everything in his power to keep his word.
    Hey... I'm your onii-chan. Mom calls me Reen, but the truth is my name is really Kazuma, and I'm a hero from another world. I promise you I'm going to be the best onii-chan ever. No one is ever going to hurt you or make you cry or make you hungry, and no one, is ever, ever going to treat you like a skaa. I promise...
  • Discard and Draw: Tanya loses her last life's magic, but is reborn a full Mistborn.
  • Dramatic Chase Opening: The story begins with Tanya chasing Kazuma across the rooftops.
  • Due to the Dead: Kazuma is poor, but he still takes off his shirt to cover the body of a dead girl that was killed as a result of his actions. He then carries her to the river where he prays to every god he knows that she may be given happiness in her next life.
  • Edible Bludgeon:
    • After his final fight with the Big-Mouth girl and the rest of her group, Kazuma notes that he caved in at least one skull with a loaf of skaa bread.
    • After he walked in to their apartment to see his mother having slapped Vin, Kazuma punches the woman so hard that she bounces, kicks her while she's down, and then throws a loaf of bread at her head for good measure. He notes that the bread probably did the most damage.
  • Entertainingly Wrong: Tanya's schtick, as she repeatedly misunderstands the Final Empire and its norms.
  • Establishing Character Moment: For each of our protagonists:
    • Kazuma evades a Mistborn despite his sack of loot, blows her up mid-air, returns to his lair, and starts pouting when his sister isn't around to hug him hello before he switches to discussing arson of the nobility.
    • Tanya single-mindedly chases an infamous thief, walks into a trap, and wakes up in a foul mood, but she doesn't take her temper out on any of her subordinates despite their similar failures to track the thief's escape even as she worries about losing status and needing human shields against other Allomancers.
  • Experienced Protagonist: Both Kazuma and Tanya have already been through an whole adventure on different worlds before being reincarnated again.
  • Family Man: Everything Kazuma does is for the well-being of his little sisters.
  • Foil: Kazuma and Tanya are this to each other naturally, especially given the fact that they are born on opposite sides of this world's social class.
  • Helmets Are Hardly Heroic: Tanya wears a wooden helmet, while Kazuma does not, and between them Kazuma is the one fighting against the fascist Final Empire...but Tanya is far more heroic than other Mistborn and Steel Ministry members who also go without helmets.
  • How We Got Here: The first chapter illustrates a running fight between Kazuma as the Masked Chivalrous Thief and Tanya as the latter attempts to apprehend the man whose been stealing from her family for as long as she can remember. After she fails, she gives orders to the rest of her unit and returns to Keep Tekiel to report to her superiors. The scene then transitions to Kazuma returning to a rebel hideout and conversing with Dockson, Ham, Clubs and the rest of the Mistborn crew. The following two chapters begin with the death and subsequent reincarnation and rebirth of the two isekai characters in the world of Scadrial.
  • Jerk with a Heart of Gold: Tohmes may be a Lazy Bum, but he still handles Tanya gently in recognition of her age despite his griping, and he's too lazy to be deliberately tyrannical to those below him.
  • Karmic Thief: Kazuma tends to only steal from Nobles who have done something to warrant it, such as the Tekiels after they murdered an innocent girl in front of him, or the street Nobles who wished to attack Vin because they despised the sight of a happy skaa.
  • Killed Midsentence: The Big-Mouth girl, who thought it would be a good idea to ambush Kazuma after he had already handed her and her group their ass on multiple occasions, didn't even get the chance to finish threatening to harm Vin before the Adventurer vaporized her head with Lightning.
  • Lazy Bum: Tanya's Mistborn teacher, Tohmes, has a particularly unacceptable vice for a Mistborn: laziness. He likes to do as little as possible, but is still industrious enough to put in a little work in the short term if it means less trouble for him in the future.
  • Misplaced Retribution: A passing noble hears Kazuma complaining about how much a Crapsack World Scadrial is and sends his guards to kill the complaining skaa. Kazuma throws a wet ball of ash into the passing noble's face as retaliation before escaping and climbing up the nearest rooftop only to watch the guards grab a little girl with a passing resemblance to Kazuma and slit her throat instead.
  • Mundane Luxury: To skaa, everything may as well be a luxury. To Tanya, library access is a luxury and reward.
  • Mundane Utility:
    • A lot of Kazuma's Adventurer Skills simply help him check for enemies or start campfires, but he uses them to great effect when fighting.
    • Tanya receives an allowance because she's expected to use coins for fighting. Instead of using them for their expected purpose, however, she uses them for their original purpose and purchases a large quantity of metal nails to fight with.
  • Mugging the Monster: A group of skaa children attempt to mug and eat Kazuma. He leaves them scattered throughout the alley, completely exhausted through Drain Touch with himself entirely fine thanks to Heal.
  • My Eyes Are Leaking: Kazuma after he thinks back to the good times with his party, hearing their imaginary voices.
  • Noodle Incident: One of House Tekiel's Mistborn "died in a bizarre ball accident four years ago that they were still not quite sure hadn't been an assassination."
  • Normal Fish in a Tiny Pond: Kazuma wasn't a particularly strong Adventurer in Belzerg, but he is an absolute monster by Scadrial standards. His experience and Wrong Context Magic, combined with his opponents' lack of Magic Resistance, allows him to practically massacre large groups of opponents without suffering any permanent damage.
  • Oh, No... Not Again!: Tanya's first thought after dying and being reborn (followed by her Catchphrase).
  • OOC Is Serious Business:
    • When river-burying a dead girl killed because she was mistaken for Kazuma, he prays to Eris and Aqua seriously for the girl to be reborn lucky with a loving family.
    • After burning gold and getting THREE Gold-shadows, Tanya doesn't even mentally protest being sent to bed like a child, and breaks curfew in the night to procure some alcohol when she can't sleep.
  • Playing with Fire: Kazuma uses his Fireball and Tinder skills to great effect in both arson and combat.
  • Promotion to Parent: Kazuma is the only parental figure Vin has seeing as her father wants nothing to do with her and her mother is Hearing Voices and an Abusive Parent besides.
  • Really Gets Around: Tanya's birth father sired more than half-a-dozen known half-siblings, and at least a couple unknown in the form of Vin and Iris, before he became an Obligator.
  • Reincarnate in Another World: This has already happened four times in the story so far.
    • Tanya, courtesy of both Truck-kun and Being X, has been reincarnated as Taniar Tekiel, an initially low ranking member of house Tekiel.
    • Kazuma, having managed to eliminate the Demon King in a suicide attack, has been reincarnated as Reen, Vin's older brother.
    • The little girl one of the Tekiel nobles had killed because of her resemblance to Kazuma was reincarnated by Eris as Sakura Kinomoto.
    • Iris, Kazuma and Vin's sister who is killed by their mother on Ruin's orders, is reincarnated by Aqua as Tomoyo Daidouji, Sakura Kinomoto's best friend.
  • Stealth Hi/Bye: Tanya has a flair for them, startling Tohmes during a lesson and later her maid.
  • Stepford Smiler: Before she Snapped, Tanya hid her constant rage and frustration by smiling at everyone.
  • Thief Bag: On his first outing, Kazuma uses stolen bed sheets and a pillowcase to hold his ill gotten gains. Over the years, he graduates to a much larger bag helpfully emblazoned with the words "Loot From Nobles".
  • Trademark Favorite Food: Kazuma loves meat. Tanya loves coffee, except the Final Empire doesn't have any.
  • Tranquil Fury: Kazuma is typically a pretty understanding fellow, especially by Final Empire standards, but threaten his little sister and he will calmly massacre your entire group.
    "Lightning." Cries rang out as Kazuma sent the spell through the girl's head, making it explode as the electricity went out the other side of her skull. In this world, no one had magic resistance of any sort, no equipment that was strong against elemental spells. Here, his spells were actually badass. "You're all dying now."
  • Unishment: As punishment for breaking her incompetent and boring tutor's arm, Tanya is charged with self-studying all the topics he was to have taught her, which she wanted to do anyway.
  • Wrong Context Magic: Kazuma's abilities are like nothing the Final Empire has ever seen. The reason he keeps his Adventurer abilities is because he wasn't reincarnated by a Jerkass God like Being X and because he actually managed to defeat the Devil King in his second life.
    Well, why wouldn't he have his handy Adventurer Skills? He learned them fair and square after all.