Perhaps Percy is banished with some of his friends, and they have to build a new society on the island. There could be internal conflicts as they struggle to adapt to their new situation and different leadership styles emerge. Percy has to navigate these relationships while also finding a way to get back home and clear his name if he was wrongly banished.
One plot idea could be that Percy is betrayed by a close friend who is jealous of his powers. This friend spreads false rumors about Percy being a threat to Camp Half - Blood. As a result, he is banished. Percy then has to prove his innocence while on his own, facing various monsters and challenges that test his strength and loyalty.
One idea could be that Percy is banished because of a false accusation of using his powers for evil. He then has to journey through unknown territories, facing new monsters and making unexpected allies to prove his innocence. Maybe he meets an ancient and forgotten god who offers him a deal to regain his status.
One idea could be that Naruto and Tenten are banished due to a false accusation of plotting against the village. They then have to prove their innocence while on the run. They might encounter old enemies who have also been exiled and form an unlikely alliance to clear their names.
One idea could be that the character with the Sharingan is banished due to false accusations of using its power for evil. He then has to journey alone, facing challenges and learning to control his power in new ways. Maybe he meets a group of outcasts who he befriends and together they fight against the unjust system that banished him.
One plot idea could be Naruto being banished to the world of One Piece. He could join the Straw Hat Pirates and use his ninja skills in new and exciting ways. For example, his shadow clone jutsu could be used for various tasks on the ship. Another idea is that he gets banished to the Bleach universe. He might learn about Soul Reapers and Hollows, and his chakra could be seen as a unique form of spiritual energy there. Maybe he could even train with the Soul Society to become stronger.
A possible plot could involve the banished mercenary being from a long - lost clan. The reason for his banishment was a false accusation by a rival clan. As he wanders the Naruto world as a mercenary, he discovers clues about his clan's true heritage and power. He then uses his skills as a mercenary to gather allies and resources to prove his clan's innocence and restore its honor. Along the way, he crosses paths with Naruto and his friends and they either help or hinder his quest depending on the situation.
In a 'naruto on island fanfiction', Naruto might find himself on an island that is constantly changing its geography due to some sort of powerful and unstable ninjutsu. This would force him to constantly adapt and use his ninja skills in new ways. He could also meet a spirit or entity on the island that claims to know his destiny and he has to decide whether to trust it or not. There could be a race of people on the island who are immune to normal ninja attacks and Naruto has to learn their ways to be able to defend himself and communicate with them.
A powerful sorcerer who also wants to claim the island for his own could be the main antagonist. He sees Percy as an obstacle to his plans and tries to eliminate him. The sorcerer might have control over some of the dangerous creatures on the island and use them to attack Percy.
Perhaps Naruto, in his banished state, has some new and unique abilities that Temari is intrigued by. She decides to help him master these powers in secret. As they train together, feelings start to develop. Their relationship could then be a source of conflict between Konoha and Suna as the two villages have different views on Naruto's banishment and his newfound connection with Temari.
One plot idea could be that Naruto, after being banished, crosses paths with Kurenai who is on a solo mission. She initially has her doubts about him due to his banishment but gradually realizes he was wrongly accused. They team up to face a common enemy that threatens the village from afar. This could lead to a growing bond between them.