It could be about many things. Maybe it focuses on a post - apocalyptic Naruto world where there's been a great destruction leaving behind fire and ash. It might center around characters dealing with the aftermath, like Naruto himself having to rebuild the village or face new, more dangerous threats that emerged from the chaos.
Sara Sharif was a young girl at the center of a very sad story. She was a victim in a situation that led to her death and has since become a symbol for the need to protect children from potential harm within families.
It's possible that the main characters could also include some of the antagonists from the original series. Maybe they are behind the cause of the fire and ash, or they take advantage of the chaos to further their own goals. Naruto and his allies would then have to face these enemies while also dealing with the desolate environment.
One popular Fire and Ash fanfiction might be those that explore their adventures in uncharted regions. Maybe stories where they face new and powerful Pokemon.
One possible fanfic could be that Ash accidentally sits on a hot Pokeball which causes his butt to be on fire. He then runs around in a panic while his Pokemon try to figure out how to put the fire out. Pikachu might use Thunderbolt but that just makes things worse by electrifying Ash as well.
Ash can be developed by showing his growth in understanding different fire - type Pokémon's unique needs. For example, learning how to train a Charmander that is more stubborn than others. This shows his patience and adaptability as a trainer.
One good Cate Blanchett fanfic could be one that imagines her in an alternate historical movie role. For example, a fanfic where she plays a powerful queen in a steampunk version of a historical era. It could explore her character's relationships with other fictional characters in that setting.
I'm not sure specifically about the 'Cate Beach Ghost Story'. It could be about a spooky encounter that happened on Cate Beach. Maybe it involves a mysterious figure seen at night, strange noises heard near the shore, or an old legend of a spirit that haunts the area.
Yes, there are likely some out there. You can start by looking on fanfic websites like Archive of Our Own. Just search for their names, and you'll find various stories written by fans that might be interesting.