There's also a chance it could be a misunderstood character. Maybe someone who believes they are doing the right thing by taking Harry away. They could think that his family or the current situation he is in is dangerous for him, and so they kidnap him to protect him in their own, misguided way.
Perhaps a rogue character. There could be a character who has their own motives, not aligned with the main groups in the Rance world. This person might be after some sort of personal gain, like a reward for kidnapping Harry or using him for some dark magic or technology.
It could be a rival faction. In the Rance universe, there are often different groups vying for power or resources. A rival faction might see Harry as a threat or an opportunity and kidnap him to gain an edge.
Another scenario is that the kidnappers might have some special plan for Harry. Since he was kidnapped as a baby, they could have some long - term scheme. They might be aware of some special power or potential that Harry has, even as a baby in the Rance world. So they kidnap him to control that power when he grows up.
A powerful and insane magical being from a far - off land. For example, a powerful sorcerer from a place like the Forbidden Forest that has long been in hiding. He hears of the prophecy about Harry Potter and decides to kidnap him as a baby to study his magic and use it to gain more control over his own territory.
It could also be a secret organization within the Naruto universe that we don't know much about in the original story. This organization might be aware of some hidden prophecy or potential in Naruto related to the Nine - Tailed Fox. They kidnap him with the intention of either preventing that potential from being realized (if they see it as a threat) or using it for their own mysterious ends.
It could be an old enemy of Keith's, someone from his past who has a vendetta against him. Maybe a former rival from his days in the military academy who has now turned to more devious means.
In some creative fanfiction, it could be an alternate version of Spiderman himself from a different dimension. This Spiderman has gone bad and kidnaps a fan from our dimension as part of some grand, dark plan that involves crossing dimensions and causing chaos.
A power - hungry nobleman from a neighboring land could be the kidnapper. He might believe that by having Rapunzel in his possession, he can gain some sort of political advantage or use her as a bargaining chip against her kingdom.
It could be Orochimaru. He's always been interested in obtaining powerful individuals for his experiments, and Naruko with her unique abilities would be a prime target.
It could be a new villain that has emerged, someone who is jealous of Gohan's power and wants to make it his own. This villain might be from a far - off planet and has heard of the Saiyan legend.
It could be a group of rogue Decepticons who are acting on their own. They might not follow Megatron's orders but still see value in kidnapping Arcee. Maybe they have a personal vendetta against her or think they can get rich by selling her to the highest bidder in the Cybertronian underworld.
Maybe it's a group of villains working together. They could be from different factions but united by the idea that Izuku has the potential to become a huge threat to their plans. They might kidnap him to either eliminate him or turn him to their side. Also, it could be a lone, obsessed fan of a villain who wants to prove themselves by bringing Izuku to their idol.