In this fanfiction, perhaps the kid is in danger from some dark wizards. Harry, being the hero he is, adopts the kid to protect him. He then starts to train the kid in magic, sharing all his knowledge and experiences. They might also go on adventures together, exploring hidden parts of the wizarding world that Harry himself didn't know about when he was younger.
Well, it could be that the kid has some special powers just like Harry. Harry sees himself in the kid and decides to take him under his wing. Maybe the kid is an orphan too, and Harry wants to give him a better life at Hogwarts, away from the cruel muggle world that didn't understand him when he was a kid.
One possible plot could be that the kid is a half - blood and is being bullied in the muggle world for being different. Harry adopts the kid and introduces him to the wizarding world. As they live together, the kid helps Harry heal from his own traumas. They form a bond that is unbreakable, and the kid eventually grows up to be a great wizard, inspired by Harry's kindness and guidance.
The kid could be a lost descendant of one of the old wizarding families. Maybe a long - lost relative of the Weasleys or the Blacks. Harry discovers this connection and decides to adopt the kid to preserve the family's legacy.
Well, one possibility is that Harry realizes Fenrir's tragic backstory and decides to help him change. Maybe he uses magic to suppress Fenrir's werewolf side and tries to integrate him into the wizarding society. Harry could teach Fenrir about friendship and loyalty, and together they fight against the dark forces that once exploited Fenrir.
Perhaps the girl is a huge fan of Harry Potter in the fanfiction world. When Harry discovers her, she's being bullied for her love of him and his story. So, he adopts her to protect her. He then shows her the real Hogwarts, not just the one she's read about. Along the way, they might face challenges from those who don't like the idea of Harry having an adopted daughter, but they overcome them together.
Maybe Aragorn adopts Harry because he sees the potential in him to be a great leader. He takes Harry under his wing to groom him into a leader who can unite different groups, just as Aragorn united the races in Middle - earth. Aragorn would expose Harry to the politics and power dynamics of Middle - earth, and Harry could use his own experiences of dealing with the wizarding world's power struggles to adapt and contribute. Also, Aragorn's strong moral compass would influence Harry to make more ethical decisions in his life.
One possible plot could be that Hawkgirl discovers Harry Potter in a dangerous situation in the wizarding world. Maybe he's being hunted by dark forces more intensively than in the original story. Hawkgirl, with her combat skills and unique abilities, decides to take Harry under her wing. She could teach him some of her fighting techniques, which would be a new aspect for Harry as he mainly focuses on magic in the original. This would lead to Harry having an edge in battles against the dark wizards and creatures.
In such a fanfiction, perhaps the plot could involve Harry seeing a child in a difficult situation, like an orphan in the wizarding world who has no family due to a dark wizard's attack. Harry, having been an orphan himself, feels a strong connection and decides to adopt the child. He then teaches the child about magic, love, and how to face the challenges in the wizarding world.
The plot could involve a prophecy that ties Tsuna and Harry together. Harry, being the hero he is, feels responsible for Tsuna. He adopts Tsuna and brings him to live in the wizarding world. Tsuna is amazed by all the magical things around him, from the moving portraits to the flying broomsticks. Harry teaches Tsuna about the dark forces in his world and how to fight them. Tsuna, with his own tenacity, starts to train hard. Along the way, they make new friends together and face many challenges that test their bond and their magical abilities.
Well, perhaps Harry could find Sasuke in a strange magical realm that connects the Naruto world and the wizarding world. Harry, being the kind - hearted person he is, decides to take Sasuke under his wing. He could introduce Sasuke to Hogwarts, and Sasuke might be amazed by the magic there. He would learn spells instead of ninjutsu, and they could have adventures together fighting against dark wizards who might be interested in Sasuke's special powers.
In this fanfiction, maybe the kid has some special power that Naruto notices. So Naruto adopts the kid to protect him from those who might misuse his power. Along the way, Naruto helps the kid come to terms with his power and they form a really strong bond, facing all kinds of challenges from other villages and ninja clans.
Maybe Percy discovers a kid in a difficult situation, like being an orphan in a monster - infested area. He decides to take the kid under his wing to protect him from harm.