In this fanfiction, Aoshi might kidnap Kaoru due to a misunderstanding. Maybe he saw her with some people he thought were enemies of his, and without fully investigating, he took her away to protect what he believes in. He could later realize his mistake and struggle with how to make amends.
Well, perhaps Aoshi kidnaps Kaoru because he believes she has some information crucial to his clan's honor. He might be acting out of a sense of duty that has been warped by his past traumas.
Perhaps there could be a new character introduced who becomes the hero. This character could be someone who has been observing Aoshi's actions from the shadows and decides to step in to save Kaoru when they realize the situation is getting out of hand.
A plot might be set in a different time period, say a historical setting. Hikaru and Kaoru could be from two different social classes, but they meet secretly. Their relationship develops over time, and the kiss could be a symbol of their defiance against the social norms that try to keep them apart. It could also be a modern - day plot where they are dealing with the pressures of school and family, and their kiss is a moment of pure emotional release in the midst of all the chaos.
Well, it could be that Okashira has some strange motives for kidnapping Kaoru. Maybe he's jealous of Kaoru's popularity or something else in the fictional world. He might be planning to use Kaoru to gain something, like information or power within the story's context.
One possibility is that Artemis has been misinformed. Some enemy of Percy has tricked her into thinking that Percy is a danger to the demigods. So she kidnaps him to stop him from causing harm. But as she keeps Percy captive, she slowly realizes that she has been deceived when Percy starts to explain his side of the story and the real threats he has been fighting against.
The plot could involve the Phantom seeing Christine as his only salvation from his lonely and tortured existence. So, he kidnaps her with the intention of making her understand his world. He may show her his musical creations, hoping she'll come to love him in return. However, Christine might be initially terrified and try to escape.
In some fanfictions, Aizawa might be under the influence of a villain's quirk that makes him act against his will. So, he kidnaps Izuku, but later on, he realizes what he's done and tries to make amends. This could lead to a story full of drama and redemption.
One possibility could be that Minato was under some kind of mind - control spell. Maybe an enemy of Konoha managed to manipulate him into thinking that Naruto was in danger by being in the village. So, Minato kidnaps Naruto to take him to what he believes is a safer place. But as the story unfolds, Naruto tries to figure out what's wrong with his father and tries to break the spell on him.
One possible plot could be that Klaus believes Bonnie has the key to a powerful spell that could help him gain ultimate power. So he kidnaps her. He whisks her away to a remote island. There, he tries to persuade her to help him, using both threats and false promises. He might start off being cruel but then gradually start to have some strange respect for her as she resists him.
In one scenario, Hiei might kidnap Keiko to use her as bait to draw out Yusuke. He could be forced by some powerful enemy who wants to get revenge on Yusuke. Hiei, being a rather complex character, might not be entirely happy about this but feels he has no choice. He would keep Keiko in a hidden location, perhaps in the demon world where it's hard for Yusuke to reach easily.
One possible plot could be that Gray kidnaps Lucy as part of a misguided attempt to protect her from an unknown danger. He might think that by taking her to a secluded place, he can keep her safe from a powerful enemy that is targeting her.