One common plot twist is that Sasuke might seem to have finally given in to Naruto's pursuit, but then it turns out to be a ruse to achieve some other goal. Maybe he wants to get close to an enemy Naruto is also after. Another twist could be that Naruto discovers a hidden side of Sasuke's reasons for leaving that changes his whole approach to bringing him back.
In many fanfictions where Naruto refuses to give up on Sasuke, their relationship is often portrayed as extremely deep and complex. Naruto's unwavering determination to bring Sasuke back is a central theme. It shows Naruto's loyalty and his belief in the bond they once shared as teammates and friends. This loyalty can be seen as a symbol of Naruto's true nature, always believing in the good in people, especially Sasuke, no matter how far Sasuke has strayed.
One possible reason could be that Naruto realizes Sasuke is too far gone in his quest for revenge. Naruto might see that no matter how much he tries, Sasuke won't change his ways, so he gives up. For example, if Sasuke keeps attacking innocent people in his pursuit of power to defeat Itachi's enemies, Naruto might finally lose hope.
One common plot twist could be that Naruto initially resists the arranged marriage because she values her freedom and ninja career. She might see it as a hindrance to her goals. Another could be that Sasuke has some hidden motives for agreeing to the marriage, like protecting Naruto from a greater threat in the ninja world. And sometimes, a third party might try to break up the arranged marriage, believing it's not in the best interest of either Naruto or Sasuke.
One common plot twist could be that Sasuke actually planned to be 'kidnapped' to some extent. He might have wanted to gain power from Orochimaru in a more secretive way. Another could be that Naruto and his friends discover Orochimaru's lair much sooner than expected, leading to a premature rescue attempt. And sometimes, Orochimaru may not be the real mastermind behind the kidnapping, but rather a pawn of a more powerful enemy.
In some fanfiction, Naruto could give up on Sasuke if he falls in love and his new relationship makes him see things differently. His new partner might convince him that Sasuke is a lost cause or that he should focus on their own future instead. Also, if Naruto suffers a major setback in his own life, like losing a dear friend in a fight related to Sasuke, he could lose the will to keep chasing Sasuke. This would be a very emotional and complex turn of events in the fanfiction world.
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.
A great plot twist could be that Sai is secretly working for an enemy all along. He has been feeding information about Naruto and Sasuke to this unknown foe. This would completely change the dynamics between the three characters.
A great plot twist could be that Neji, who was thought to be a loyal Leaf Village ninja, is actually a spy for an enemy village. This would completely change the dynamics between him, Naruto and Sasuke. They would have to figure out how to deal with this betrayal while also dealing with other threats to the village.
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.
One common plot twist could be Sasuke losing his Sharingan abilities in this new world but gaining a completely different and unexpected power. Maybe he discovers a magic that only exists in this other world which he has to learn to control from scratch. Another plot twist might be that the people in this other world mistake him for a prophesied hero or villain due to his appearance and skills, which forces him into a role he didn't expect. Also, there could be a plot twist where Sasuke finds out that his family is somehow alive in this other world, but they have no memory of their past life in his original world.