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.
There could also be other characters like Kaoru's friends. They would play an important role in trying to rescue her. For example, a very close friend who has some special skills, like being good at tracking or fighting, could be a key figure in the rescue attempt. And maybe there's an authority figure, like a detective or a wise old mentor who helps in the search.
The idea of Kaoru being kidnapped by Takeda Kanryu in a fanfiction is quite interesting. It could lead to a lot of character development. For Kaoru, it might be a journey of self - discovery and finding strength in a difficult situation. Takeda Kanryu, on the other hand, might have his own backstory that led him to this extreme action. The fanfiction could also show how the relationship between these two characters changes over time, from enmity to perhaps something more complex like understanding or even a form of redemption.
Kaoru could try to gain the trust of one of the kidnappers and then use that opportunity to escape. For example, if there's a less hardened kidnapper among them, she could pretend to befriend them and then make a run for it when they let their guard down.
There could potentially be such a fanfiction, but it's not a very common or well - known trope in general fanfiction. It really depends on the fandom or the creative minds of individual fanfiction writers. Maybe it exists in a very niche or specialized area of fan - created works. You might also consider reaching out to fanfiction communities or forums to ask if anyone has heard of or read such a story.
Kenshin would be extremely worried. He'd immediately start looking for her. He has a strong sense of justice and protectiveness towards Kaoru. So, he'd use his Battousai skills to track down the kidnappers as quickly as possible.
One possibility is that Kaoru's friends or allies will immediately start a rescue mission. They could track down Takeda Kanryu's hideout and try to free Kaoru through a fight or some clever plan.
Well, she might be held for ransom. Maybe the kidnappers think that as a nurse, she has access to valuable medical information or drugs that they can sell on the black market.
It could be a jealous coworker. Maybe they feel that Kaoru is getting all the attention or a promotion they wanted. Another possibility is a patient who has become obsessed with Kaoru during their treatment. Or perhaps it's someone from Kaoru's past who has a grudge against her.
One plot idea could be that the kidnapper has a personal vendetta against Kaoru. Maybe Kaoru witnessed something she shouldn't have, and the kidnapper wants to keep her quiet. Another idea is that it's a case of mistaken identity, and the real target was someone else in the same hospital. A third idea could be that a deranged fan of Kaoru's kidnaps her in an attempt to make her their own, thinking they can 'protect' her from the outside world.