I recommend the novel "Kidnapping the Protagonist". This science fiction and time-travel genre novel tells the story of a male protagonist who possesses a kidnapping system and is constantly transported to different worlds to become the main character. The story revolves around the protagonist being kidnapped by the female lead. The novel is full of surprises and excitement, and I believe you will enjoy it.
It could be a new character created specifically for the fanfiction. Maybe a young scientist who is working on a project related to the super - soldier serum. Since Bucky has a history with the serum, this would create an interesting dynamic.
A young adventurer could be a great main character. They are always exploring new places, so it's likely they could end up in the wrong place at the wrong time and get kidnapped by witches.
It could be a young child who strays too close to the sewers where Pennywise lurks.
It could be a young woman who is a stowaway on a ship and gets discovered and kidnapped by pirates.
It could be a young adventurer. This type of character would be full of curiosity and a sense of exploration. Their kidnapping by pirates would be a major setback to their adventure plans, but they would also be quick to look for ways to turn the situation around.
It could be an over - enthusiastic fan who has always wanted to meet the Jokers. They get kidnapped by accident during one of the Jokers' wild stunts, and then they have to deal with the crazy situation.
Perhaps it could be a minor character from Twilight who somehow ends up in a situation where they are kidnapped by a creeper. This would give the writer a chance to explore that character more deeply and in a completely different context. For example, a character like Jessica from Twilight could be the main character. She's not a central figure in the original story, but in this fanfiction, she could have a whole new adventure.
It could be Robin, the Boy Wonder. If Catwoman kidnapped Robin, Batman would surely be on a mission to rescue him. Robin is young and inexperienced compared to Batman, so he could be an easy target for Catwoman, and his rescue would make for an exciting story.
Well, usually it leads to a lot of tension and drama. Maybe the kidnappers have some demands or there's a rescue mission in the works.
The kidnapped character could use their own hidden jutsu skills to break free. For example, if they have a teleportation jutsu they've been hiding, they could use it when Sasuke is distracted. Another way is to appeal to Sasuke's emotions. If they can remind him of his better nature or a past event that made him more empathetic, he might let them go.