Perhaps in the fanfiction, there is a prophecy or a vision that Tsunade has seen which makes her think that Naruto needs to be in a certain place or situation for the greater good. And she is so desperate to fulfill this that she resorts to kidnapping Naruto. This could lead to a story where Naruto initially resists but then comes to understand Tsunade's reasons as the story progresses.
It could also be for power. Some evil shinobi might believe that by capturing Naruto and somehow extracting the Nine - Tails' power, they can become extremely powerful. They might have some sort of dark jutsu or experiment in mind that requires the power of the Nine - Tails which is sealed within Naruto.
Another motive could be revenge. Maybe some in Iwa still hold grudges against Konoha for past conflicts. Since Naruto is a prominent figure in Konoha, kidnapping him would be a way to strike back at the village. They might think that by harming Naruto, they can make Konoha suffer.
One possible motive could be to gain control over Naruto's power. Since Naruto has the Nine - Tails within him, Danzo might want to use that power for his own political or military gains. He's always been power - hungry and sees Naruto as a tool to achieve his goals of making Konoha stronger in his own way, which might involve more underhanded and controlling methods.
Well, Obito could be doing it out of revenge. He has a long - standing grudge against the Hidden Leaf Village. Naruto is seen as a symbol of hope in the village. So, by kidnapping him, Obito could be trying to strike a major blow to the village's morale and show that their so - called 'hope' can be easily taken away.
Naruto might be initially confused. He trusts Tsunade, so being kidnapped by her would be completely unexpected. He would probably start by asking her why she's doing this.
The motives could be revenge. Somebody who has been wronged by Deidara or the Akatsuki in general might kidnap him to get even. For example, a village that was destroyed by his explosives could seek vengeance.
Perhaps Kaguya steals Naruto fanfiction because she wants to use the creative ideas within it for her own gain. The fanfiction might have unique plot twists or character developments that she can adapt for her own purposes. It could also be a form of jealousy. If the fanfiction is highly praised and she isn't getting the same kind of attention in the Naruto universe, she might resort to stealing it.
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.
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.