Seriously, reading SAO fics has made me appreciate how different authors handle this. Some just throw them into a generic fight, but the good ones dissect their actual fighting styles from the Aincrad arc. Kirito's solo instincts versus Asuna's 'Flash' precision. The best teamwork scenes aren't about them being perfect; they're about that moment of silent, unplanned synchronicity. Like when Asuna covers a blind spot Kirito didn't even announce, or when Kirito deliberately draws aggro to set up her finishing strike.
I hate when writers make Asuna just a healer or support, by the way. That feels like a massive misunderstanding of her character. She's a frontline duelist. The teamwork works because they're both apex predators, just with different hunting patterns. Their partnership in 'Mother's Rosario' is a much better template for post-canon fics than the early Aincrad stuff, honestly.
It’s less about choreography and more about trust. You can write the flashiest sword moves, but if the scene doesn't carry that weight of mutual, absolute reliance, it just feels like two OP characters happening to fight the same monster.