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.
One possible plot could be that the kid is from a village that was destroyed by an enemy. Naruto, having experienced his own share of loss, feels a connection. He adopts the kid and tries to give him a normal life in Konoha. However, the kid has a lot of trauma from the past. Naruto has to help him heal, while also training him to be a strong ninja. There could be a sub - plot where the kid's past comes back to haunt them, and they have to fight against the remnants of the enemy that destroyed the kid's village.
Perhaps the kid is from a foreign land that Naruto visited during one of his missions. The kid could be an outcast in his own place because of some unique trait. Naruto, being the kind - hearted person he is, decides to adopt him. It could be that the kid has a different kind of chakra or a strange mark on his body that makes others afraid of him, but Naruto doesn't care.
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.
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.
The kid could be a young demigod whose parents are unknown. Maybe he's been living on the streets, hiding from monsters, until Percy finds him.
Well, one possibility is that Ichigo, with his strong sense of justice, takes Naruto under his wing. He could teach Naruto some of his combat skills from the Bleach universe. Maybe Naruto would learn to use a sword in a new and unique way, combining it with his own ninja techniques.
One possible plot could be that Naruto discovers an orphaned child during one of his missions. The child has unique chakra abilities but is shunned by the village. Naruto, remembering his own childhood of being an outcast, decides to adopt the boy. He then trains the boy not only in ninja skills but also in values like friendship and perseverance.
In a 'Madara Adopts Naruto' fanfiction, perhaps Madara adopts Naruto because he sees a kindred spirit in him. Madara might want to mold Naruto into a powerful force to reshape the ninja world according to his own ideals. Naruto, on the other hand, could either resist or be influenced by Madara's views, leading to an internal struggle within Naruto as he tries to balance his own values with what Madara is teaching him.
Well, perhaps Naruto finds Scootaloo in a difficult situation, like she's lost or alone. Naruto, being the kind - hearted hero he is, decides to take her under his wing. He might teach her some of his ninja skills, like how to move quietly or be more perceptive. And Scootaloo could learn a lot from Naruto's never - give - up attitude.
In this fanfiction, perhaps Erza is found by Naruto when she's injured. Naruto takes her back to Konoha. Since he has a big heart, he wants to give her a home. As she recovers, they start to bond. Erza might be amazed by the chakra system and Naruto could be intrigued by her magic. They could then go on adventures together, with Naruto protecting her like a father figure at first, and later they become equal partners.
Well, it could be that Arceus, being a powerful and god - like Pokémon, sees Naruto's potential and decides to take him under his wing. Maybe Arceus helps Naruto gain new powers related to Pokémon abilities. For example, Naruto could learn to use Pokémon moves in his battles against the Akatsuki or other enemies in the Naruto world.