Well, perhaps Inuyasha is under some sort of dark spell. He might be influenced by an evil force that makes him see Kagome as a threat to his freedom or something he needs to control. So, he kidnaps her and takes her to a remote place. Kagome, being the strong - willed character she is, tries to reason with him and break the spell's hold on him.
One scenario could be that Inuyasha's demon side gets the better of him. He has always had a complex relationship with his demon nature. If his demon instincts take over completely, he might view Kagome as his possession. So, he kidnaps her. Kagome, on the other hand, uses her knowledge of Inuyasha and the spiritual powers she has to try and bring back the Inuyasha she knows, while also dealing with the situation of being held captive.
In a possible plot, Inuyasha could be tricked by a more powerful demon into believing that kidnapping Kagome is the only way to protect her from a greater danger. He takes her away against her will, but Kagome soon realizes that Inuyasha is acting out of a misinformed sense of protection. She then has to find a way to make him see the truth and together they face the real threat.
Kagome would probably be shocked at first. Then she would start yelling at Inuyasha, demanding to know why he's doing this. She's not the type to just sit there and take it.
It could be that Inuyasha kidnaps Kagome as part of a deal. He made a deal with another powerful being to save someone else he cares about. He doesn't want to do it but feels he has no choice. Kagome, being the strong - willed person she is, then tries to find a way to get out of this situation while also helping Inuyasha out of his moral dilemma.
One possible fanfiction could be about Inuyasha in his full demon form and Kagome's journey to understand and reach out to him. Maybe she uses her spiritual powers to calm him down when he's on the verge of losing control. It could explore their relationship dynamic in this unique state of Inuyasha.
At first, their relationship would be severely strained. Kagome would be angry and scared, feeling betrayed by Inuyasha. She might not trust him at all anymore.
Inuyasha would also be worried about Kagome's safety. He knows how devious Naraku can be. He might call out to Kagome as he gets closer to Naraku's lair, hoping to hear her voice and know that she's still alive. His reaction would be a mix of anger, worry, and determination to rescue the woman he loves.
Another idea is that Inuyasha's full - demon form attracts the attention of an ancient and evil force. This force wants to use Inuyasha for its own dark purposes. Kagome has to fight against this force, not only to protect Inuyasha but also to save the world. It would involve a lot of action and some difficult decisions for Kagome.
One possible plot could be that Sesshomaru kidnaps Kagome because he believes she has some power or knowledge that could be useful to him. Maybe he thinks she can help him find a powerful weapon or a way to gain more territory. He might keep her in his lair and at first be very cold towards her, but as time passes, he starts to see her in a different light.
Perhaps in the fanfiction, Koga kidnaps Kagome believing she has some special power that can help his wolf demon tribe. He might think that she can heal the sick among them or bring good fortune to their land. However, Kagome doesn't actually have this power, and she has to convince Koga to let her go while also trying not to anger him too much. As she's held captive, she might learn more about the wolf demons and their way of life, which could be an interesting aspect of the story.
Their different backgrounds make them an interesting pair. Inuyasha is a half - demon from a feudal era, while Kagome is a modern - day girl. This contrast allows for a lot of creative exploration in fanfiction. Writers can play with how they interact, with Kagome introducing modern concepts to Inuyasha and Inuyasha showing Kagome the ways of his world.
Some great Inuyasha and Kagome fanfictions include those that focus on their adventures after the end of the series. For example, 'A New Beginning' which shows them building their life together in the feudal era. It has really good character development and stays true to their personalities.