Naruto could develop by learning to adapt his ninja skills to a more modern and zombie - filled setting. He might become more cautious as he realizes the different threats here compared to his ninja world. Rika could develop from being a normal schoolgirl to a more confident and brave fighter. She could learn from Naruto's fearless attitude and start using her own wits in more daring ways.
One common theme is adventure. Since they are both from the Pokémon universe, the fanfics often involve them going on Pokémon - hunting adventures together.
One common theme is the development of their relationship. It could be about how they gradually understand and support each other. Another theme might be adventure - based, where they go on quests together in the digital world.
Sure. You can try searching on some popular fanfic platforms like Archive of Our Own. Just type in 'ash x rika fanfic' in the search bar and you'll likely find a variety of stories written by different authors.
Their relationship in the fanfiction is likely to be full of mutual understanding. Since they are getting married, they must have a deep connection. Takato might be the more gentle and patient one, while Rika could be the strong - willed partner. They balance each other out.