Another idea for a fanfic is a character - exchange. Picture Yuna from Final Fantasy X spending some time in the world of Final Fantasy XV. She could bring her unique brand of white magic and summoning abilities to Noctis' group. In return, Noctis or one of his friends could visit Spira (the world of Final Fantasy X) and introduce their own combat techniques and technology. This would create a lot of interesting interactions between the characters and their respective worlds.
A possible fanfic could explore the concept of the crystal in Final Fantasy XV and the Fayth in Final Fantasy X. Maybe the crystal's power has some sort of connection to the Fayth, and characters from both games have to figure out how to use this connection to restore balance. This could involve a journey across both worlds, with characters learning about each other's cultures and histories along the way.
A possible crossover aspect is the world - building. The post - apocalyptic world of 'owari no seraph' and the more fantastical world of 'Final Fantasy XV' could merge. Maybe the characters from 'Final Fantasy XV' end up in the world of 'owari no seraph' and have to deal with the vampire - human conflict. They could bring their own technology and magic, which would change the balance of power in the 'owari no seraph' world.
One interesting crossover could be the use of magic spells from 'Harry Potter' in the world of 'Final Fantasy XV'. For example, a character from 'Final Fantasy XV' might learn the Patronus Charm to fend off daemons. Another could be the appearance of Hogwarts - like buildings in the 'Final Fantasy XV' landscape. Maybe Noctis and his friends could attend a magical school similar to Hogwarts.
The worlds themselves can be blended. The post - apocalyptic world of Final Fantasy XV and the more tropical and spiritual world of Final Fantasy X are very different. A fanfic could involve a rift between the two worlds that the characters have to close. As they travel between the worlds, they learn about the different cultures, like the technology - based society in Final Fantasy XV and the religion - centered society in Final Fantasy X. This would create a rich tapestry of interactions and plot developments.
One common theme is the exploration of different powers. Since both RWBY and Final Fantasy XV have unique power systems, fanfics often explore how these powers interact. For instance, the Dust in RWBY and the Magic in Final Fantasy XV can create some really interesting combinations.
In some Naruto x Final Fantasy fanfiction, the summons in Naruto could be related to Final Fantasy summons. Like the toads in Naruto could have a connection to a similar creature from Final Fantasy. This would create unique interactions between the two universes.
Some cool crossovers might include Naruto's summoning jutsu being used in the world of Final Fantasy X - 2. He could summon giant toads or snakes, which would be a strange sight in Spira. The Al Bhed language from Final Fantasy X - 2 could be something Naruto characters have to learn. And perhaps the Farplane in Final Fantasy X - 2 could have a connection to the afterlife in the Naruto universe. This could lead to some really deep and emotional storylines where characters from both worlds interact with the concept of death and the afterlife.
One idea could be exploring the backstories of the main characters in more depth. For example, Noctis' training as a prince and his relationship with his father before the events of the game. Another could be a fanfiction set in an alternate universe where the Astrals have different roles or relationships with the humans. Maybe a story where Noctis and his friends have to face a new, unexpected threat that wasn't in the original game.
There's a fanfic called 'Dawn of the Crossover' which is quite popular. In this fanfic, the combat styles of RWBY characters are blended with the magic and weaponry of Final Fantasy XV. It also delves into the relationships between characters from both series, creating a lot of engaging drama. For example, Ruby's speed and Crescent Rose are paired with Noctis' warp strikes in some really cool action scenes.
One interesting crossover could be the characters from Naruto having to deal with the complex summon system in Final Fantasy X. For example, Naruto might be intrigued by the Aeons and try to form some sort of bond with them. Another aspect could be the sharing of jutsu and magic. Maybe a character from Final Fantasy X learns how to use a chakra - based jutsu, or vice versa.
One interesting concept could be a crossover of the magic systems. In Final Fantasy XV, there's the use of elemental magic and powerful spells. In Naruto, there's ninjutsu. A fanfiction might explore how a character from one universe adapts to the other's magic. For example, a Naruto character learning to use the warp - strike ability from Final Fantasy XV in a battle. Another concept could be the interaction of the different races. The elves in Final Fantasy XV and the various clans in Naruto could have some really unique interactions, like how the Uchiha clan's sharingan might react to the magic - using races in Final Fantasy XV.