Well, Jessie and James' love story is a rather interesting one. They are part of Team Rocket, constantly scheming. But beneath all that, there's a connection. They've been through so much together, from getting blasted off by Pikachu countless times to coming up with new plans to capture Pokémon. Their love might not be the typical romantic love at first sight. It's more like a love that has grown out of mutual understanding, loyalty, and the shared experiences of being in Team Rocket.
One key moment could be when they protect each other from other villains or Pokémon. Another might be when they share a rare moment of vulnerability after a particularly tough defeat. Also, the times when they come up with plans together, showing their teamwork and the trust they have in each other, are important in their love story.
They might love fanfiction because it offers new perspectives on their own lives. In fanfictions, their characters can be developed in ways that the original show might not have explored fully. For instance, they could be portrayed as more complex individuals with deeper backstories.
Some fanfics that are worth reading are those that explore their backstories in relation to their love. For example, 'Jessie's Heart, James' Soul' which goes back to their childhoods and how certain events led to their growing affection. It's really interesting to see how the author weaves in their past experiences to build a more complex and believable love story between them. Another is 'Love on the Run' which has them running from Team Rocket to be together, with lots of action and romance combined.
Comedy - centered fanfictions could be great too. Given their somewhat bumbling and comical nature in the show, a fanfiction full of humorous situations, like them trying to cook a meal for their Pokémon but everything going hilariously wrong, would surely make them laugh and thus be something they'd enjoy.
Well, apart from the big fanfic platforms, you could also check out Pokemon - specific fan communities on social media. Sometimes, members share their own fanfics or recommend ones they've read. For example, on Reddit, there are Pokemon fanfic subreddits where you might find some great Jessie and James love stories. Also, Tumblr can be a good place to look, as there are often fanfic recs floating around.
I'm not sure specifically as there could be many different versions of such a fanfiction. But generally, it might be about Ash coming to the rescue of Jessie and James in some sort of dangerous or difficult situation they are in within the Pokémon universe.
One common theme is unrequited love finally being realized. For a long time in the Pokémon show, their relationship was more of a comical partnership, but in fanfiction, the kiss can be a moment of that underlying love coming to the surface.