Hard to say for sure. Their relationship has its ups and downs, and her feelings for Kazuya aren't straightforward. It depends on how you interpret different scenes and interactions.
Well, it depends on how you interpret the story. But in the end, there are clear signs that Chizuru and Kazuya end up together. Their interactions and feelings for each other build up throughout the manga.
One common theme could be love and affection. Since it involves a 'beso' (kiss), the fanfic may focus on the deepening relationship between Ash and Serena.
There are many fanfic platforms out there. Some popular ones apart from Archive of Our Own are FanFiction.net. Browse through their Pokémon section and look for stories with Ash and Serena in the tags. Then, you can skim through the descriptions or reviews to find the ones that might have a 'beso' scene as you desire.
After the first beso, their relationship might become more confident. They start to be more open about their feelings for each other. They hold hands more often and share more affectionate glances.
Well, perhaps in terms of character development. Just as Kazuya in some fanfictions might have complex backstories and growth arcs, Naruto also has a very in - depth character development journey. His experiences from being an outcast in the village to becoming a hero are full of twists and turns, much like how a well - written Kazuya fanfiction might explore the character's evolution.