A/N: Like most of my fics, I have no idea why I think this was a good idea.

….

Kazuma V Tanya

by Shadow Crystal Mage

Prologue: Thief V Mistborn

Disclaimer: Brandon Sanderson has an army of over 20,000 clones all linked in a writing hive mind. That's the only explanation that makes sense! Also, he owns the Mistborn series. Konosuba is owned by Akatsuki Natsume and is godly. Carlo Zen made Tanya.

….

The mists of Luthadel were alive with the sounds of battle.

In the dark of night, two figures fought along the city's rooftops. One flew through the mist-filled air, glass knives swishing dangerously, a cloak made up of strips of gray flapping around them from the wind of their swift movements. The other moved erratically, as if in a wild panic, yet every movement swiftly got them out of harm's way, buying them precious time even as they were encumbered by a huge sack over one shoulder. Large letters helpfully identified the sack as 'Loot From Nobles', and a black and white mask covered their face, showing only his mouth.

"Ha! Close, but not close enough you stupid noble! What, has spending your days getting yourself off by stepping on skaa made you fat and slo– YOW! Ha, still missed me!"

The Mistborn said nothing even against the face of this taunting, not letting themselves be distracted by the words. Slim, swift limbs covered in sensible black moved with practiced precision to concentrate the power of their movements toward a single point as they struck at the thief yet again, only for the thief to fall off the roof to a lower level, sending the Mistborn flying over them.

"Hah! Your stomach-upsetting powers are no match of my luck st– GAH!" The gloating was interrupted as the Mistborn flipped over, facing them upside-down as a spike-like object, dark against the night and mist, was steelpushed towards the thief. Only an awkward, legs-wide jump saved the thief from life as a non-Steward eunuch. "Still missed!" the thief crowed before one hand quickly flashed towards their back, and tossed something at the Mistborn. It was round and pale and going straight for her. "Here's something right back, you rusting asshole!"

No lines pointed towards the projectile, but the Mistborn took no chances. She flared steel, pushing on all nearby metal and launching herself diagonally back the way she came, spinning and righting herself gracefully as she turned back towards the thief. He was grinning at her, one arm upraised and–

Something slammed into the side of her head, and her vision suddenly went white as a fine white powder erupted from the delicate paper bundle that had struck her. Not just a ball, but a ball on a string. Her senses, enhanced by a low tin burn, helpfully told her it was a mixture of flour and fine sawdust before she was overwhelmed at the enhanced irritation of the fine granules on her senses. Rather than stop burning tin, however, she increased the burn and burned pewter again for a beat despite her running dangerously low on it, letting her ignore the burning of her eyes, the feeling of the fine granules in her nose and on her skin, and concentrated on her hearing, trying to track the thief, trying to watch out for attack–

"Tinder."

The whisper was loud in her ears, and she immediately threw another spike towards the source of the voice, dropping pewter and flaring steel to send the projectile as fast as Mistbornly possible.

A squelch and a scream of "Fuck!" deafened her, even as her tin enhanced senses felt the heat source coming closer…

Her senses, still burning tin, were overwhelmed as the cloud of flour and sawdust she was in exploded.

….

The Mistborn woke up in an alley, inside a circle of identical-looking gray-clad figures wearing tattered gray scarves over their mouths and identical hoods over their heads. One held a hooded lantern, its shutter only partly open and shaded. Going by the sensations on her face, she'd suffered burns. Well, there went going to the balls for the next few weeks. What a shame. She'd have to remember to thank that thief with a painless death when she next met him. She burned pewter, feeling some to her body's aches and pains become less urgent as the metal enhanced her body like an old friend visiting with cake. Her stores were still low though, and unlikely to last long enough to make it to Keep Tekiel. "Vial," she demanded, then grimaced. Her voice had been hoarse. "Vial," she repeated, voice firmer. "Report."

She accepted the glass vial one of them men handed her. She braced herself, then burned tin to shock herself completely awake, managing not to wince as she burns on her face became fiery agony. The smells of the alley, as to be expected of the public hygiene practices of this pseudo-Victorian world, reeked of waste and decay. Quickly, she swished the vial, finding the correct weight for one of their pre-measured pewter vials, and felt the filed notches on the outside lip of the glass, still sealed with a layer of wax. Popping the tube open, she downed the contents, not reacting to the taste of metal and alcohol solution as she swallowed the metal flakes.

The man who'd handed her the vial, her second in command Wynt, straightened to attention, only the subtle line of knots on the edge of his hood identifying him from the similarly attired mistings and hazekillers around him as she looked up at him. "The thief escaped, captain," he said, voice level and bland as she got to her feet. By now, they at least knew they had nothing to fear from her when it came to bad news. "Smoke and Cloud tried to follow, but they lost sight of him in the mist, and the metal line of his loot disappeared soon after. Given how quickly he disappeared, it's likely he had a bolthole arranged. Do you want the rest of the crew to start searching door to door?"

Wynt had been in the garrisons before she'd recruited him, and the Mistborn could hear the special non-tone of a junior officer giving their CO an opportunity to not make the wrong decision.

"No," she said. "Have the rest of the hazekillers return to base. We're going back to the keep. See to it. And see if we have burn cream in the first aid kit."

If they didn't, she'd have to find a way to add it. Medicines didn't last long in storage, but she had the House's resources to draw on.

Feeling the back of her head, she winced. Her wooden helmet was cracked from the fall. She could feel it through her mistcloak's hood. "I'll need a new helmet," she said. "Perhaps we can steal something from our thief and add a mask in case he has more fiery surprises. See if the padding of this one can be salvaged."

"Yes, captain," Wynt said. Good man. Almost as good as Visha, but with no coffee about they had no way of putting that to the test. "The carriage with the supplies is this way."

He began to lead her out of the alley, the other members of the squad easily falling into step around her. She definitely didn't feel any height envy. No, not at all. At no point in the conversation had they ceased keeping watch on the ends of the alley, the many windows on both sides, and the misty sky above. After all, there was more than just some self-proclaimed 'Masked Chivalrous Thief' abroad in Luthadel these days, and while she could potentially deal with any Mistborn from rival houses, there was a chance her burns could become infected.

"All right," she said once everyone had managed to fit inside the extended carriage. With the curtain drawn, they could finally let more light out of the lantern. "Report. Specifically, what took you so long?"

There were no exchanged nervous looks, no shuffling, only strict professionalism as her squad gave their reports of the night's events one by one, having long since gotten used to reporting to her despite her stature. Lady Taniar Tekiel, or 'Tanya' to people who insisted on still infantilizing her, would have been proud, had this been a review before the House's Lord, but not tonight. Tonight, her eyes were hard and her blue-eyed gaze intense as she listened to the reports of her squad and began to plan for any future encounters, holding still as Shot, their coppercloud and a very distant Tekiel cousin applied what little medicine they had to her face. More importantly, she began to plan how she was going to spin this failure as something positive to her superiors. Her father had long since renounced any authority over her and her mother had died at childbirth, but the rest of the house, especially her aunt Verin and that opportunist cousin Edgwin would surely use this incident to undermine her and try to take away control of her squad. She couldn't allow that to happen, not when she needed as many meat shields between her and enemy allomancers as possible.

Curse you, Being X!

….

The door to the lair's kitchen opened and the victorious Masked Chivalrous Thief, covered in soot and skaa clothes under his distinctive green mantle, walked in with a smug smile. "I'm home!" he sang happily, arms opened wide expecting a hug.

"If you're expecting anyone to touch you while you're that filthy, you're in for a long wait," Breeze drawled.

"Clean that floor. I run a clean shop here, boy," Clubs snapped with a glare.

"Where's the loot?" Dockson said, not looking up from his ledgers.

"Hey, welcome back," Ham greeted him cheerfully.

The not-so-triumphant Masked Chivalrous Thief scowled. "I'm not into old men. Imouto-chan! Onii-chan is back!"

"If you're looking for your sister, she's back at the Renoux Manor for the night," Dockson said. "The loot?"

"Damn it! I fought that stupid Mistborn for nothing!" There was a beat. "Hey old man, I'm going to need more sawdust."

"Are you eating it, boy? Why would you need so much sawdust for?"

"Setting nobles on fire. You own a carpentry shop, you know how it works."

"Lord Ruler boy, are you out of your mind?"

"Is that a no?"

"Fine, I'll have the boys gather it up for you at the end of the day."

"I'm going to be making a lot more bombs, so have them save all of it every day."

"Not in here, they won't!"

"Dockson, I need a warehouse to store stuff for setting the city on fire."

"Don't you have your own lair?"

"You want to mix sawdust with paint? Are you insane? Then the city WOULD catch fire!"

"I'll ask Kelsier, see what he thinks. Now, the loot?"

"Tell him I'll start with the nobles so he'll say yes."

"You know," Breeze said to Ham, "We used to be honest thieves. Now here we are consorting with arsonists. What happened to us?"

"You got old and boring," the blunt Masked Chivalrous Thief said. He pointedly looked at Breeze. "And fat."

"He means you," Breeze told Ham.

"No, I definitely mean the alcohol-marinated emergency ration."

"Definitely you," Breeze said.

"The loot?" Dockson persisted.

"Stashed it to get those metalpushers off my trail. I'll pick it up tomorrow," the tired Masked Chivalrous Thief said with a yawn. "Or the day after. Or the one after that. It's really hard to get motivated when I'm little sister deficient…"

"See, comments like that are the reason there are weird stories about you two," Ham said.

"Give me names of whoever is lewding my little sister like that. My little sister is too pure to hear such things!"

"Kazuma, your little sister is going to grow up someday, you know."

"She can grow up when she's forty!"

The Masked Chivalrous Thief took off his mask as he reached for the wine.

Clubs pulled it back. "You can have some when you clean the ash you tracked in."

"Oh, come on! You're not going to begrudge someone who's worked a long, hard day one glass, are you?"

Clubs was unmoved. "No clean, no wine."

"Damn it, I want a new party!"

….

- To be continued…

….

A/N: So, in regards to Tanya, the alternate plan was to have her as either Kelsier's little sister or an Obligator in charge of investigating the signs of rebellion. The former felt a bit Mary Souixish, the latter… Was seriously considered. Originally, I was going to have her turn because they tried to forcibly recruit her into an Inquisitor…

Then I changed my mind.

Please review, C&C welcome.

Until next time, this is Shadow, signing off.