One idea could be exploring the characters' new lives in the real world after the events of the game. For example, how Joker adjusts to normal school life again while still having his Persona powers. Another could be a story where the Phantom Thieves discover a new threat that is related to the remnants of the Metaverse they thought they had defeated. Maybe a new group is trying to use the Metaverse for evil in a different way.
Yusuke is another underrated character. In a post - game fanfiction, he could be traveling around to find new inspiration for his art. Along the way, he might encounter some Shadows that are related to the concept of beauty in a way that challenges his views. This would not only give him more character depth but also show how his Persona abilities are still relevant outside of the main game's plot.
The architecture in Persona 5 is also very distinct. Your male OC could have a special connection to a particular location in the game, like Leblanc coffee shop. Maybe he works part - time there and has some interesting conversations with Sojiro. This would help to ground him in the game's environment.
Yu is often very popular. He's the main character, and in New Game Plus fanfiction, his already - established character can be further developed. He might have new skills or a deeper understanding of his Persona powers. Another popular one is Yosuke. His friendship with Yu and his growth as a character are always interesting to explore in fanfiction.
One interesting crossover could be the Phantom Thieves entering the world of No Game No Life. They might use their Personas to compete in the various games in that world. For example, Joker's Arsene could give him an edge in a high - stakes card game.
Joker is often a very popular character. He's the main protagonist, and in fanfiction, his growth and new experiences in New Game Plus can be really exciting to explore.
Yu Narukami is often a popular character. His leadership skills and calm demeanor make him stand out, especially in the high - stress situations of the King's Game. He's likely to come up with clever strategies to deal with the challenges.
One interesting storyline could be the protagonist exploring different Social Links in a more in - depth way. Since it's New Game Plus, they might have more knowledge and use it to strengthen relationships faster. For example, they could quickly form deep bonds with the SEES members and uncover hidden aspects of their personalities.
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.