Another reason might be revenge. There could be a character who has a grudge against Inuyasha or someone close to him. So, they kidnap him to make him suffer or to use him as bait to draw out his friends. For example, if there was a demon whose family was slain by Inuyasha in the past, they might kidnap him for revenge.
It could also be a case of mistaken identity. Some other powerful force might be after a different half - demon with similar powers as Inuyasha. And in the chaos of the situation, they end up kidnapping Inuyasha instead. This could lead to all sorts of comical or dangerous situations as Inuyasha tries to convince them of their mistake.
Another motive could be related to her family. Maybe there was some sort of blood feud or an old grudge against the Grangers. The kidnappers could have thought that by taking Hermione, they could get revenge on her family. In some fanfictions, there are secret magical families that have long - standing rivalries, and Hermione's kidnapping could be part of that.
The Naraku would be a likely kidnapper. He is always plotting against Inuyasha and trying to get his hands on the Tessaiga. Kidnapping Inuyasha would be a way for him to either steal the sword or find a way to break Inuyasha's spirit so that he can no longer oppose him.
One possible motive could be ransom. Maybe someone wants a large sum of money from Philip's family or friends. Another could be revenge. Perhaps Philip has unknowingly wronged someone in the fanfiction world, and this is their way of getting back at him.
Well, it might be that the kidnapper has some sort of medical need that they think Kaoru can fulfill. Since she's a nurse, they could be desperate for medical attention that they can't get through legal means. Or perhaps there's a villain in the fanfiction who just wants to create chaos in the hospital by taking one of its nurses, and Kaoru happened to be the unlucky one.
Perhaps it's about love in a twisted way. Sebastian might be obsessed with Clary and think that by kidnapping her, he can make her his. In some fanfictions, characters with a warped sense of love do extreme things like this. He could also be trying to use Clary as a pawn in a larger scheme against the Shadowhunters. By having her in his control, he can manipulate the situation to his advantage.
One possible motive could be misinformation. Maybe Bucky was misled to believe the OC was a threat to someone he cares about. So, he kidnapped the OC to prevent them from causing harm.
Maybe Dumbledore believes that Harry has some hidden power that is being corrupted by the environment at Hogwarts. So, he kidnaps Harry to a secluded place to train him and help him control this power without any distractions or negative influences from other students or even some of the teachers.
It could be that Peter has some sort of knowledge or information that the kidnappers want. For example, he might have accidentally witnessed a crime and the criminals want to keep him silent.
One possible motive could be power. In some fanfictions, there might be dark wizards or witches who believe that Hermione, being a very intelligent and magically gifted child even from a young age, could be used to their advantage. They might think that they can control her magic or use her knowledge for their evil plans, like finding ancient magical artifacts or unlocking powerful spells that are otherwise inaccessible.
In these fanfictions, a common motive for Hermione's kidnapping could be her unique knowledge. She is known for her extensive reading and understanding of magic. Some villains might want to use that knowledge for their own gain. For example, they could be looking to uncover ancient and powerful magic that Hermione has studied. Regarding the adoption part, it might be a way for those who kidnap her to control her future. They could think that by 'adopting' her, they can shape her into someone who serves their interests better. It could also be related to a prophecy. If there is a prophecy that involves Hermione in some way, certain groups might kidnap her to either prevent the prophecy from coming true or to make it come true in a way that benefits them.