Man, that pairing has more flavors than a Lumiose City bakery. In the XY anime their dynamic was all about unspoken support and Serena’s one-sided crush gradually becoming mutual respect. Fanfiction really digs into that ambiguity.
A lot of writers focus on a post-series gap, like what happens after that almost-kiss at the airport. There’s a popular trope where they reunite as adults, with Ash still wandering and Serena trying to make it as a performer, and they have to navigate the awkwardness of unfinished conversations. I’ve read a few where Ash actually has to learn emotional vocabulary from her, which feels true to his character—he’s a battle genius but emotionally dense.
The evolution isn’t always smooth. I’ve seen fics that start them off as a couple already, then throw a massive conflict like differing life goals at them. That’s when you see real growth, because they have to argue and compromise. Some of the best stuff I’ve read has Serena struggling with Ash’s constant travel, asking if she’s just another person he’s leaving behind. It gets pretty heavy, but it makes their eventual understanding feel earned.
My personal favorites are the ones that keep it low-stakes, though. Just them traveling together again, with the easy camaraderie of the show but with a new layer of quiet affection. No grand declarations, just sharing a blanket during a snowstorm on the road to Snowbelle City. That’s the good stuff.