One interesting aspect is the different interpretations of the game's characters. In persona 5 novelization fanfiction, authors can explore the inner thoughts and backstories of the characters in more depth than the game might show. For example, they can expand on a character's motivation for joining the Phantom Thieves.
Finally, start writing! Use vivid descriptions to bring the world of Persona 5 to life in your fanfiction. Describe the characters' actions, emotions, and the settings in detail. For example, when writing about a palace, describe its unique architecture and the traps within it. And don't forget to proofread and edit your work to make it as polished as possible.
Perhaps the fanfiction focuses on the cultural clash between the two groups. The Persona 4 characters are from a small town, while the Persona 5 crew is from the big city. Their different ways of handling things and their unique Personas could lead to some interesting interactions. For example, Yu and Joker might have different leadership styles that they have to reconcile in order to succeed against the shadows.
I think the 'Fourth Shinobi War Novelization Fanfiction' might focus on exploring the characters' inner thoughts during the war. For example, it could show Naruto's determination in more detail, how he was feeling while facing such a huge threat.
Maybe the Velvet Room attendants from both games somehow get their worlds mixed up. Igor from Persona 5 and Margaret from Persona 4 have to work together to set things right. This leads to the characters from both games interacting. The Phantom Thieves might learn some new combat techniques from the Investigation Team and vice versa. They could then use these new skills to face a common threat that emerges from the merging of their two realities.
Maybe there's a strange distortion that merges parts of Inaba and Tokyo. The characters from both Persona 4 and Persona 5 find themselves in this strange new place. They start to notice that the Shadows in this merged world are more powerful and have new abilities. The Investigation Team and the Phantom Thieves must figure out how to adapt their Personas and strategies to fight these new threats while also dealing with the cultural differences between their two groups.
One great fanfiction about Persona 3 Hideotoshi could be a story that delves deeper into his backstory. Maybe it could explore his relationships with other characters in the game. For example, it could show how he interacted with his teammates during a particularly difficult mission. This would add more depth to his character and give readers a better understanding of his role in the Persona 3 universe.
It's hard to say how popular persona adult fanfiction is in general. It likely has a niche following within the larger Persona fan community. Some fans may be interested in the more mature interpretations and stories, but it's not as mainstream as regular Persona fanfiction.