Maybe he'll have to learn a whole new type of magic. In the other world, the rules of magic could be completely different. Instead of using wands, they might use their minds directly to cast spells. So Harry would have to adapt quickly to survive and figure out how to use this new magic system.
Well, he could face a whole new set of challenges. Maybe the magic there works differently. For example, spells he uses on Earth might not have the same effect, or he could encounter a powerful dark force that he has to figure out how to defeat without the help of his usual Hogwarts friends and professors. He'd have to rely on his own wits and the skills he's learned over the years to survive and overcome difficulties.
In the 'harry potter goes to the sixth world fanfiction', it's possible that Harry Potter will meet new friends or foes. He could face different kinds of challenges related to the new world's magic system. For example, the rules of magic in the sixth world might be very different from what he's used to in Hogwarts. He might have to figure out how to use his existing skills in new ways to survive and thrive in this strange new place.
In this fanfiction, Harry might encounter new magical creatures unique to that country. He could learn different kinds of magic that are practiced there. For example, if he goes to a country in Asia in the wizarding world, he may discover spells related to nature spirits which are not common in his homeland.
Well, in the new timeline, Harry could find that Voldemort has already won. This would mean he has to figure out a way to either change the past to prevent this future or find a way to defeat Voldemort in this new, much more difficult situation. It would be a huge challenge for him.
Well, Harry could be really confused at first. Ouran is a very different world from Hogwarts. He might be shocked by the opulence of Ouran Academy and the strange club system there. Maybe he'd try to find a way to fit in while still being true to his wizard self.
Well, he might make new friends. In a different school, there could be new magical traditions and spells for him to learn. He'd also face different challenges compared to Hogwarts.
He might encounter new and strange creatures. In many fanfictions, Percy could meet unique magical beings that don't exist in his own world. For example, he could come across sentient plants that can communicate or floating islands with their own mini - ecosystems.
Maybe Harry has some strange magical illness that normal wizards can't cure. So he has to seek help from a very special doctor who might have some unique remedies.
Perhaps he would be seen as an oddity at Alfea. After all, he comes from a completely different magical system. But his reputation as the 'Boy Who Lived' might precede him. Some might be in awe of him, while others might be skeptical. His presence could also stir up some rivalries among the students at Alfea who are used to their own hierarchies. Harry would have to find his place among the fairies and deal with any potential jealousies or hostilities.
Well, he might encounter new magical creatures unique to America, like the Thunderbird. He could also visit American wizarding schools and be amazed by their different teaching methods compared to Hogwarts.