Well, without having read this exact fanfiction, it's hard to say precisely. 'Pain kidnaps Sakura' in a fanfiction could be a plot device to create drama and conflict. It could be set in the Naruto universe if that's where Pain and Sakura are from. The story might focus on how Sakura's friends try to rescue her or how she tries to escape on her own from Pain's clutches.
I'm not sure specifically as it could be a very specific fan - made story. It might involve the character Pain from a particular series kidnapping the character Sakura. Maybe it's a story exploring dark themes, power dynamics, or the rescue of Sakura within the context of the fanfiction world.
You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own (AO3). Just use the keywords 'pain kidnaps sakura' in their search bars and see if any relevant stories pop up.
There could be many interesting storylines. For example, they might start as enemies but then find common ground through some unexpected events. Maybe they are forced to team up to face a greater threat in the ninja world. This could lead to a deepening of their understanding of each other's beliefs and values.
It could be that Naruto has lost his sanity temporarily. The stress of being a hero, the constant battles, and the losses he has endured might have taken a toll on his mental state. In this state of instability, he may see Sakura as a symbol of something he wants to preserve or protect, but his way of doing so is through kidnapping. Or there could be a new villain in the story who has the ability to make Naruto act out of character, and this villain's plan involves Naruto kidnapping Sakura.
One common theme is unrequited love. Sakura often suffers from loving someone who doesn't return her feelings, which causes her great pain.
In some fanfictions, Sasuke could be under the influence of some dark power or curse. This power might compel him to kidnap Sakura. For example, a dark entity might want to use Sakura's abilities or her connection to Sasuke for its own evil purposes, and Sasuke, being unable to fully control himself, follows its commands.
It could also be a matter of desperation. Perhaps there is a threat to the village or someone she loves dearly, and she believes that Naruto holds the key to solving the problem. But instead of asking him directly, she kidnaps him in a hasty and ill - conceived plan. This could lead to a lot of drama and character development as Naruto tries to understand her actions and they both work towards resolving the real issue.
Perhaps in the fanfiction, Madara kidnaps Sakura because he realizes her potential as a medic - nin. He wants her to heal his old wounds or maybe study her unique healing abilities to find a way to make himself invincible. He could keep her in a hidden lair and force her to perform medical experiments on him.
Well, if Sasori kidnaps Sakura in fanfiction, it could lead to a really intense situation. Sasori is a formidable opponent. Sakura, on the other hand, has her medical ninjutsu skills and her growing strength in combat. She could potentially use her medical knowledge to her advantage. For example, she might be able to use some herbs or substances in the place where she's held captive to create a distraction or even a weapon. And there could be a rescue mission by her friends from Konoha, which would add more drama to the story.
Well, one possible plot could be that Gaara has some misunderstanding. Maybe he believes Sakura has some knowledge or power that can help his village in some way. So, he kidnaps her to force her to share that. But then as the story unfolds, Sakura tries to make him understand that she can't help as he thinks and they start to see each other in a different light, perhaps even becoming friends in the end.
In such a fanfiction, Deidara might use Sakura as a hostage to bargain with the Hidden Leaf Village. He could be after some secret jutsu or valuable information that the village has.