Oh, this is one of those pairings where the tropes kind of write themselves, isn't it? The most dominant one is definitely 'Friends to Lovers,' but the Pokémon journey framework twists it into this specific 'Training Partners to Lovers' flavor. They've got this established rhythm—Ash's chaotic, instinct-driven battling style clashing and melding with Misty's more technical, Water-type mastery. Fics love to play with the tension of them being these incredibly skilled, competitive trainers who are also deeply familiar with each other's strengths and flaws. It's a foundation built on years of shared, high-stakes travel.
Another massive one is the 'Reunion Fic,' set years after the original series. The premise is almost always that they've grown apart, pursued their own goals (Ash in Alola or the World Coronation, Misty running the Cerulean Gym), and then they cross paths again. The nostalgia hits hard, and all those unresolved feelings from when they were kids come rushing back, but filtered through adult maturity. Authors get to explore how time has changed them while the core connection remains. You'll also see a ton of 'Injury/Comfort' tropes, often after a tough battle or a wild Pokémon attack, where one has to nurse the other back to health. It forces a vulnerability they'd normally brush off with bickering.
Then there's the niche-but-persistent 'Aura Guardian Ash' trope, which sometimes gets woven in. It's less about the supernatural element itself and more about how Misty reacts to this hidden, profound aspect of him she never fully understood. It creates a power dynamic shift. Honestly, the tropes are comfort food for a reason—they take that classic, bickering-but-devoted dynamic from the anime and give it the romantic payoff the show could never explicitly deliver. The fandom has been doing it for over two decades, and the formulas still work because they're so rooted in the characters' established history.