Well, one possibility could be that Harry discovers a magical portal that leads to another planet. He leaves Earth because he's on a quest to find a powerful magical artifact that is said to be hidden in a far - off galaxy. Once he leaves, he has to deal with all kinds of strange new creatures and different forms of magic.
I recommend "The Last Cultivator on Earth". The protagonist of this novel not only sealed a passage to save the Earth, but also went to the Ming River to extradite his master, explore the lost past of the Nine Realms, and walk a path that defies the heavens. This novel combined elements of fantasy and oriental fantasy. It was very interesting and attractive. I hope you like my recommendation. Muah ~
In a 'Percy Jackson leaves earth' fanfic, he might end up in a whole new realm of gods and monsters. Maybe he discovers a parallel universe where the rules of the Greek gods are different. He could encounter new versions of his friends or enemies and have to learn new powers to survive.
" I Really Just Want to Go Back to Earth " was a sci-fi novel about interstellar civilization. It told the story of the protagonist who was accidentally sent to outer space and gradually adapted to life in outer space. However, he always missed Earth and finally decided to return to Earth. I hope you like this theme.
If Goku leaves Earth, his family would be greatly affected. Chi - Chi would be worried sick, and Gohan and Goten would have to grow up faster. They might become more independent and focus on their own power development. In the story, this could lead to new character arcs for them.
Perhaps he'll meet other demigods who have also left Earth for various reasons. They could form a new group and face new challenges together. For example, they might have to deal with a powerful alien being who wants to use their demigod powers for its own evil purposes. Percy would then need to use his wits and strength to lead the group and find a way to defeat this new enemy.
He could go to the Underworld of another planet, if such a place exists in the universe he lands in. It might be filled with different kinds of dead souls and ruled by a different kind of Hades - like figure.
One possibility could be that Harry Potter leaves Earth to explore other magical realms in the universe. Maybe he discovers a planet where magic is used in completely different ways than on Earth. He could encounter new magical creatures and make friends with beings who have powers he's never seen before.
There's a chance he meets a group of nomadic magic - users. These are people who travel across the universe in search of new sources of magic. They could introduce Harry to different forms of magic that are not based on the traditional elements like fire, water, earth, and air that he's used to on Earth. Instead, they might use things like starlight or cosmic energy as a basis for their spells.
He might leave to protect Kara and the unborn child. Maybe he discovers that there is some kind of danger following him that could put them in jeopardy, so he decides to sacrifice his time with them to keep them safe.