Perhaps Percy is lost and ends up in the Japanese mythological world. Amaterasu, seeing his unique powers from a different pantheon, decides to help him find his way back. Along the way, they exchange knowledge about their respective mythologies. Percy teaches her about the Greek gods and their quirks, while Amaterasu imparts wisdom about the Japanese spiritual world. This could lead to a mutual respect and a new friendship that bridges the two mythologies.
A plot could involve a dark force that is draining the power of both the Greek and Japanese mythological realms. Percy Jackson and Amaterasu are chosen as representatives of their worlds to investigate. They meet and at first have trouble understanding each other due to cultural and mythological differences. But as they face challenges together, like battles against mythical beasts sent by the dark force, they learn to work together and combine their powers. For example, Percy could use his demigod strength to hold off the beasts while Amaterasu uses her sun - based attacks to destroy them.
One possible plotline could be that an enemy tries to seduce Percy to turn him against his friends. This would create a lot of internal conflict for Percy as he has to fight against the charm or allure of the seducer while staying true to his comrades.
One possible plotline could be that Chuchi somehow ends up in the Percy Jackson universe. Maybe she has a mission there and Percy helps her out. And during the process, they develop a special bond.
Well, in a fanfiction, a plotline could be that Percy Jackson is on a quest and somehow crosses paths with Voldemort. Voldemort senses Percy's power and wants to study it. Percy, not knowing much about the wizarding world, initially mistakes Voldemort for just another monster. As they interact more, they realize that their worlds are more intertwined than they thought. Another plot could involve a powerful artifact that both of them are after. The artifact has the power to change the balance of both their worlds. So they are in a race against each other to get it, but along the way, they start to understand each other's motives and might even consider working together to keep the artifact out of the wrong hands.
A possible plotline could be Percy seeing the movie and getting into an argument with another camper about whether Hercules' deeds were more impressive than his own. They could start listing their respective adventures and how they overcame challenges, leading to a friendly competition within the camp.
In this fanfiction, there could be a plotline where Percy is initially confused and scared about being the father of Chaos. He then embarks on a journey to find out more about his new role. Along the way, he meets various characters who either help him or try to stop him. There could be a power struggle within the world of the gods as some see Percy's new position as a threat to their own power. Percy also has to deal with the moral implications of being associated with Chaos, whether to use its power for good or be consumed by it, and this internal struggle could form a major part of the plot.
A possible plotline could be that Loki, being his mischievous self, accidentally gets transported to the world of Percy Jackson. Percy at first is suspicious but then realizes Loki can be an ally. They join forces to stop a powerful dark force that threatens both their worlds. Maybe this dark force is a combination of Greek and Norse mythological evils that only their combined powers can defeat.
One possible plotline could be Percy having to fight against other champions of different deities who see him as a threat. Another is that he has to find a way to combine his new role with his loyalty to his friends and the Olympians. For instance, he may be forced to make a choice between following Pontus' orders that might seem harsh to his friends or standing by his friends and risking the wrath of Pontus.
A third plotline could be Percy's search for a powerful artifact or knowledge in Tartarus that could help him in his future battles or save his friends. Along the way, he discovers secrets about the origin of the gods or the true nature of Tartarus itself, which changes his understanding of the world he thought he knew.
One plotline could be Percy leading the Titans in a war against the gods. He might use his knowledge of the demigods' weaknesses to plan attacks. Another could be Percy trying to convert other demigods to his Titan side, causing division among them.
Well, perhaps in the fanfiction, Percy is tortured by Kronos in a way that involves his demigod powers being slowly drained. This would make him feel weak and vulnerable, which is a huge contrast to his usual strong self. His torture could also be a way for Kronos to try and break his spirit so that he can turn Percy to his side. Meanwhile, the gods might be debating whether or not to interfere, adding another layer of conflict to the story.