The story likely involves the Sailor Scouts using their powers to protect the world. There could be new magical items or transformations. Maybe they have to travel to different realms to fight the new threats. It also might explore more of their backstories and how they became the Sailor Guardians in the first place.
One could also write a fanfiction about a school exchange program. Hogwarts students could visit the Sailor Moon Cosmos schools and vice versa. The cultural shock would be huge. For example, the Hogwarts students would be used to using wands, while the Sailor Moon Cosmos students might use their transformation powers and magical items in different ways. There could be some friendly competitions between the students of both universes, like a magic - using race or a knowledge - based quiz about different magic systems.
Love and loyalty are also big themes. The Sailor Senshi are extremely loyal to Usagi, and there are often undertones of platonic love in their relationships. They would sacrifice a great deal for her, and this is explored in many different ways in various fanfictions, like one where a Senshi risks her life to save Usagi from a powerful dark force.
In a Harry Potter and Sailor Moon Cosmos fanfiction, the characters' personalities would create some really engaging scenarios. Hermione would probably be fascinated by the technology and different planets in the Sailor Moon universe. She might try to analyze how their society works compared to the wizarding world. And Sailor Moon herself, with her kind and brave nature, could form a great friendship with Harry. Their combined strength could be used to fight against a new threat that somehow affects both universes.
One great 'Sailor Moon Senshi x Usagi' fanfiction is 'The Bond Beyond the Stars'. It beautifully explores the deep connection between the Sailor Senshi and Usagi. The story has some really heart - warming moments where their relationships are tested and strengthened.
One common theme is the crossover of powers. For example, Naruto's ninja techniques might be combined with the Sailor Senshi's magical powers. It creates a new and exciting dynamic.
The beauty of Sailor Cosmos crossover fanfiction is that it can break the boundaries of the original Sailor Moon story. Writers can introduce new villains or allies for Sailor Cosmos. They can also rewrite parts of the Sailor Moon mythology to fit the new crossover elements, creating a fresh and unique narrative.
One great thing about Sailor Cosmos crossover fanfiction is the unique character combinations. You can see Sailor Cosmos interact with characters from other universes, like superheroes from the Marvel or DC worlds. It creates really interesting and unexpected storylines.
Another great one is 'Naruto's Sailor Moon Adventure'. It's a fun read where Naruto somehow gets involved in the Sailor Moon's battles and quests. The author does a great job of mixing the two storylines, and the character development of Naruto within the context of the Sailor Moon world is quite engaging.