It could be that Fem Sasuke is under some sort of mind - control when she kidnaps Naruto. A powerful enemy, like Orochimaru or a new villain, might have used a jutsu to make her do this. As the story progresses, Naruto would then have to find a way to break the mind - control on Fem Sasuke while also dealing with the situation of being kidnapped.
One possible plot twist could be that the 'Uzumaki' who kidnaps Naruto is actually an impostor. Maybe it's someone with shape - shifting abilities who wants to use Naruto for some dark purpose. For example, they could be trying to extract the Nine - Tails' chakra from Naruto in a more brutal way than the Akatsuki ever planned.
Well, one possible plot twist could be that Kohana has a hidden motive that's not as evil as it seems at first. Maybe she's being controlled by a greater force and Naruto realizes this and tries to save her instead of just escaping. Another could be that Kohana is actually from a long - lost clan that has a prophecy related to Naruto, and the 'kidnapping' is a way to start fulfilling that prophecy.
One possible plot twist could be that Sakura has been secretly training a new jutsu and uses it to outwit Orochimaru at the last moment. For example, she might have developed a genjutsu that can counter Orochimaru's mind - control techniques. Another twist could be that Naruto and Sasuke arrive just in time, but instead of a straightforward rescue, they find that Sakura has made a deal with Orochimaru in order to gain some powerful knowledge. This could lead to a rift between her and her teammates.
Perhaps Kai kidnaps Elena to force her to help him with something. He might need her doppelganger blood to break a curse on himself or his family. In the process, Elena discovers a side of Kai that she didn't expect, and they form an unlikely alliance against a common enemy that emerges during the ordeal.
One possible plotline could be that Sasuke has been misled by some false information. Maybe he believes that the female Naruto is in some way a threat to Konoha's future. So he kidnaps her to keep her away from the village. However, as he spends time with her, he realizes his mistake and they end up working together to clear up the misunderstanding.
One possible plot twist could be that Sasuke initially rejects the idea of having a baby. He might be worried about his own goals and how a family would interfere. However, as time passes, he realizes his love for Fem Naruto and the baby and decides to embrace his new role.
Well, perhaps the plot could involve Hermione actually getting through to Tom Riddle in some way. Since she's so intelligent and empathetic, she might start to make him question his dark ways while being kidnapped. This could lead to a really interesting internal struggle within Tom. Also, there could be a twist where the kidnapping is part of a much larger plan that involves other dark wizards or witches, and Hermione has to figure out how to not only escape but also stop this bigger conspiracy. Or it could be that Hermione discovers a secret about Tom Riddle's past during her captivity that she can use to her advantage.
Another plot twist could be that an enemy uses their relationship against them. The enemy could spread rumors or false information to create chaos and turn the ninja world against them. Naruto and Sasuke would then have to fight not only to protect their relationship but also to clear their names and prove that their love doesn't mean harm to the ninja world.
Perhaps Fem Sasuke in this fanfiction has a different view of the world. She might believe that Naruto is a threat to her goals or to the future of the ninja world she envisions. It could also be that she has some deep - seated emotional pain that she blames Naruto for, and that leads her to kill him.
A possible plot twist could be that Sasuke's vampire condition was actually a curse placed on him by an old enemy of the Uchiha clan. This would add a whole new layer of mystery and revenge to the story. Another twist could be that Naruto discovers he has some sort of power that can either nullify or enhance Sasuke's vampire abilities. It would put their relationship in a new light as Naruto has to decide what to do with this newfound knowledge.