[A/N: I kind of dared myself to make Karin awesome, and here is the result…This takes place at some ambiguous time after Sasuke's fight with Danzou and Karin being taken into Konoha.]
Excuse Me, Miss (But You're on Fire, or Why Antagonizing Someone Sasuke Chose as a Teammate is a Bad Idea.):
"Tsunade-shisou, you can't be serious about this!" Sakura protested. "She used to work for Orochimaru, for goodness' sake!"
"But she is also a skilled medic," Tsunade pointed out. "And after what has happened, I don't think we have much to fear from Karin."
Sakura huffed. "Fine."
"Good!" Tsunade's smile was positively devilish. "Then why don't you take the chance to get to know her? After all, you'll be working together."
"Of course," Sakura replied, positively beaming. The smile vanished as soon as she turned away, and she clenched a fist in anticipation. "Don't worry, I'll get to know her all right."
…
Karin wasn't hard to find. She had only been in the village a few weeks (not counting the time she had been in the hospital as a patient or in the interrogation department) and tended to stay in the areas she was familiar with.
Sakura caught up with her at a ramshackle little okonomikayi stand. "Karin," she growled.
Karin turned. "Sakura." She raised her eyebrows a little as she saw Sakura's tense stance and clenched fists. "What's wrong, going to take your anger at Sasuke out on me? He jilted me, too, if you recall."
"Oh, no," Sakura said, forcing her voice to remain calm. "I want to see what you're made of."
"Well, mostly water, and carbon, and phosphorus…I'm sorry, was that not what you were asking?"
"I'm challenging you to a duel!" Sakura snapped. "Right now. Choose a place."
"It's rude to interrupt someone when they're eating," Karin retorted calmly, returning to her food.
Sakura fumed at the flippant dismissal. "Fine. I'll wait."
Karin did not reply, as she was too busy taking delicate bites out of her okonomiyaki. Seeing that she would get nothing further this way, Sakura leaned against the wall of the stand and waited for her to finish.
"Okay," Karin said finally, after dawdling nigh-interminably over her last few bites. "Let's go."
…
Sakura was a bit surprised at the training field Karin had chosen for their duel. She had thought that, as a former Grass-nin before joining Orochimaru, the other kunoichi would select one of the more distant fields that rarely had the weeds chopped down, but instead she had picked out a nearly bare field scattered with rocks. Well, if she wanted to give the advantage to Sakura straight off, that was her problem.
A few other shinobi had spotted the two walking through the village and followed, guessing that they wouldn't willingly be seen together unless they were going to fight. All of Team 10 was there, although Shikamaru looked like he had been dragged along by Ino and Chouji was just there because Ino was carrying a box of crackers. Hinata had tagged along as well; she had nothing else to do as Kiba and Shino were on missions with other teams.
"Ready?" Sakura asked, taking up a position at one end of the field.
"Just a second," Karin replied, taking her glasses off. "Can you take these?" she asked, holding them out to Hinata.
"S-sure," Hinata said, taking the glasses as Karin nearly misjudged where Hinata's hand was and dropped them.
"Are you sure you wanted to do that?" Sakura asked. "You can hardly see now." She wasn't about to beat her nemesis into the ground and then have her victory discredited.
Karin smiled tauntingly. "Well, I just figured I ought to give you a chance…"
Sakura snarled in anger and punched her fist into the ground as Karin jumped into the air, flashing through a series of seals. Turning to kick a slab of rock at Karin, she gasped in surprise as bright flames suddenly burst to life around the girl's body.
"What?" Karin said as she batted away a chunk of rock with one hand, her voice distorted by the crackling of the flames. "You didn't think Sasuke dragged me around just for my looks, did you?"
Sakura ducked as Karin dove towards her, but the flames surrounding Karin were harder to avoid than taijutsu normally was. She couldn't afford to let her opponent get a strike in to create an opening to a counterstrike unless she wanted a few first-degree burns. However, Sakura had a feeling that Karin couldn't keep the firey armor up for long.
Without her glasses, Karin couldn't see clearly enough to tell what seals her opponent was making, which gave Sakura the chance to do whatever she wanted with Karin not having enough advance warning to ready a counterattack. Sakura briefly considered genjutsu, but put that idea aside, as trying to make a genjutsu allow for impaired vision was nothing she had tried before. Everything would look too clear to Karin and give the game away.
As Karin jumped toward her again, Sakura finished her series of seals and slammed her hands against the ground, bringing up a massive wall of earth in front of her. There was a solid thunk as Karin collided with the other side of it, and Sakura smiled victoriously.
She didn't have very long to gloat, however, as cracks began to appear in the wall. Sakura jumped to the side as Karin burned her way through, then kicked a rock into the girl's back before she could turn around. Karin staggered but converted her imbalance into momentum and kicked out at Sakura, landing a hit on her rib cage. Sakura winced at the burn.
Karin's flames were now beginning to peter out, and the duel quickly developed into a hand-to-hand match. Sakura had a slight advantage since Karin still couldn't see very well, but Karin had some taijutsu moves that Sakura hadn't encountered before.
They finally called a mutual halt when they were both nearly out of chakra. Karin dropped to the ground and leaned against one of the piles of dirt from Sakura's earth jutsu, and Sakura sank down beside her, too tired to really care that she didn't like Karin. "You fight better than I thought," she remarked.
"Of course," Karin retorted. "What did you take me for, you? Although, you're not as useless as I thought. Almost, but not quite."
"Karin-san, your glasses…" Hinata said as the girls started wearily back into town.
"Ah, thank you," Karin said, putting them back on. "Much better. Now, why don't you show me around your hospital?"
[A/N:…Yeah, I don't know. I just felt like writing a big fight scene, so there isn't much in the way of plot. There isn't anything in canon supporting these abilities of Karin's, but nothing contradicting, either. It kind of goes with her hair, too.]