A possible storyline could be that Percy is on a quest and gets lost in a different dimension which happens to be Gotham. Bruce Wayne, as Batman, finds him and initially suspects him to be a threat. But as they interact, they discover some similarities in their abilities and goals. They then start to dig deeper and find out they are related through a long - lost family connection that dates back to ancient times when the gods had some influence on the early human civilizations.
Another storyline could be that there's a powerful entity that is trying to take over both the demigod world and Gotham. Percy and Bruce Wayne are both chosen to fight against this entity. As they team up, they learn about each other's worlds. Percy shows Bruce the magic and power of the demigods, while Bruce teaches Percy about the technology and detective skills in Gotham. In the process, they find out that their families are connected, perhaps through a hidden family heirloom or a secret pact made between a demigod and an ancestor of Bruce's.
In fanfiction, they might be related through a shared enemy. Let's say there's a new super - villain who is causing chaos in both the demigod world and Gotham. Percy and Bruce start to work together to stop this foe, and during their investigations, they find out that there's a family connection between them. It could be something as simple as an ancestor who was part of a secret society that had ties to both the Greek mythology realm and the early settlers of Gotham.
Sure, fanfiction writers love to mix and match different fictional characters. In a story where Percy Jackson is dating Bruce Wayne, we might see Percy's Greek mythology - inspired powers and Bruce's high - tech gadgets and detective skills combine in interesting ways. For example, Percy could use his water - controlling abilities to help Bruce during a flood in Gotham, while Bruce could use his resources to help Percy protect Camp Half - Blood from some new threat.
One storyline could be that Harry, after the events in the wizarding world, decides to take a break and travels to Gotham. There he meets Bruce, and they end up teaming up to take on a new threat that combines magic and Gotham's usual criminal element. Maybe a villain who has somehow gotten hold of a powerful magical artifact and is using it to wreak havoc in the city.
One possible storyline is a competition between them. They could bet on who can solve a particular global threat faster. Bruce would use his detective skills and resources in Gotham, while Tony would rely on his Stark tech. Another could be that they get framed for a crime together and have to work together to clear their names while also finding the real culprit.
Perhaps a story where Bruce Wayne is at the police academy undercover to investigate a series of crimes that seem to be linked to someone in the academy. He has to balance his normal life as Bruce, his training at the academy, and his secret investigation. He could make friends with some cadets who end up helping him in his mission, or he could be in a situation where he has to choose between following the academy rules and doing what he believes is right to solve the case.
One possible storyline could be that Bruce Wayne gets injured during a fight with a new and powerful villain in Gotham. He has to rely on his allies like Alfred and the Bat - family more than ever to keep Gotham safe while he recovers. Another could be that he gets injured in his civilian identity, and has to hide his true nature even more carefully to avoid suspicion as he heals.
The story might also focus on the relationship between Bruce and Percy. Bruce, having lost his parents, could see a bit of himself in Percy. He could become a father figure to Percy, guiding him and protecting him. Percy, on the other hand, could bring some light and a different perspective into Bruce's rather dark world. It could be a story of growth, both for Percy as he adapts to a new life with Bruce, and for Bruce as he takes on the role of a father - figure.
In a fanfiction plot, perhaps Percy Jackson is on the run from some powerful Greek enemies and ends up in Gotham. He meets Bruce Wayne, who is intrigued by Percy's strange powers. As they spend time together, a relationship develops. Their relationship could be tested when a powerful entity from Percy's world tries to use Gotham as a base to gain power. Bruce and Percy must work together, with Percy using his demigod abilities like controlling the elements and Bruce using his Bat - gadgets and strategic mind to defeat the enemy and save Gotham and Percy's world.
One possible storyline could be exploring the immediate aftermath of Bruce's death. How does Terry McGinnis handle the loss? Another could be flashbacks to Bruce's final days, showing his last words of wisdom to Terry.
One popular one is 'The Demigod and the Billionaire'. It combines the mythological elements from Percy Jackson's world with the dark and brooding Gotham of Bruce Wayne. The story has some great action scenes where Percy uses his water powers and Bruce uses his detective skills and gadgets to fight a common enemy.