Well, he might be really confused at first. Japan has a very different culture from the wizarding world he's used to. He could encounter Japanese magical creatures that are unique to their land. Maybe he'll visit a Japanese wizarding school and be amazed at their different teaching methods and spells.
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, the magic system might be integrated with Japanese folklore. For example, instead of wands, they might use something like Japanese talismans. And Hogwarts could be a Japanese - style castle or temple - like structure, with different houses representing different Japanese clans perhaps.
Another difference is in the social structure. Japanese society has its own values and hierarchies, which can be reflected in the fanfiction. So, relationships between characters might be different. In a Japanese - inspired Hogwarts, for example, there could be more respect for elders and a different way of handling conflicts among students, which would be interesting to explore in the fanfiction.
In this kind of fanfiction scenario, it would be really interesting. Harry might have to adapt to Japanese culture while still having his magical abilities. Maybe he would attend a Japanese wizarding school that has some unique features inspired by Sekirei. For example, the school could have some sort of spirit - like the Sekirei - associated with it in a magical way.
Perhaps he'll meet a mysterious old wizard who lives in a secluded temple in the mountains. This wizard could be a master of ancient Japanese magic and could teach Harry about the spiritual side of magic that is deeply ingrained in Japanese culture. Harry might also meet a group of young Japanese witches who are training to become magical healers. They could share their knowledge of Japanese magical plants and how to use them for healing, which would be very different from the healing methods Harry learned at Hogwarts.
He might meet international aurors. These are highly skilled wizards from different countries who are experts in dark wizard catching. They could teach Harry some new combat spells.
He could meet Fleur Delacour's family. Since Fleur is from France, her family might be an important part of the French wizarding community that Harry interacts with.
Hermione would be a likely companion. She loves learning and exploring, so she'd be eager to go on a traveling adventure with Harry. Ron might also tag along, especially if there's a chance of food and adventure. Neville could be another option. He has grown a lot in courage and his knowledge of plants could come in handy in different magical environments. Luna Lovegood would be a very interesting companion too. Her unique perspective on magic and the world would add a lot of fun and mystery to the journey.