A great concept for a 'jojo persona crossover fanfiction' would be a tournament - style story. Characters from both universes are forced to participate in a battle royale. The Jojo characters would bring their Stands, and the Persona characters would have their Personas. The battles could be intense, with different strategies emerging. For instance, a Persona user might try to use psychological attacks against a Jojo character who is more used to physical combat with their Stand. And the story could also explore how the two groups of characters interact and form alliances outside of the battles.
One idea could be to have the Stand users from JoJo interact with the Personas in a battle royale - style scenario. Maybe the JoJo characters are transported to the Persona universe and have to figure out how to use their Stands alongside the Personas to defeat a common enemy.
First, you should familiarize yourself with both the Jojo and Persona universes thoroughly. Know the characters, their abilities, and the overall themes. Then, decide on a central plot. It could be something as simple as a character from one universe ending up in the other. After that, start creating your characters' interactions. For example, how would Josuke Higashikata react to meeting a Persona user? Just start writing and let your creativity flow.
Jonathan Joestar and Yu Narukami could be an interesting pairing. Jonathan's noble and chivalrous nature would contrast with Yu's more modern and relatable personality. They could learn from each other's sense of justice. Yu could teach Jonathan about the modern world and how to use some basic technology, while Jonathan could inspire Yu with his unwavering determination in the face of danger.
There's no way to really tell if it's common specifically for someone named Jojo. However, in general, reading fanfiction is a popular activity among fans of many different franchises. The Jojo series has a large and dedicated fan base, so it's likely that there are fans named Jojo who partake in reading fanfiction, but we can't say for sure how common it is without more data.
Perhaps this Jojo is interested in exploring different interpretations and stories within the Jojo universe that fans have come up with. Fanfiction often takes the existing characters, settings, etc. from the original Jojo series and creates new and unique storylines. So, this Jojo might be a big fan of the series and wants to see what other fans have imagined.
In 'Persona 4 Visual Novel', the gay persona might represent the diversity of the game's character creation and the exploration of different sexual orientations within the game's fictional world. It could add more depth to the relationships and storylines.
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.