I'm not sure which particular fanfiction you're referring to. Some fanfictions do involve Pit getting kidnapped, but without knowing the specific one, it's hard to say for certain.
Naruto might be initially confused. He trusts Tsunade, so being kidnapped by her would be completely unexpected. He would probably start by asking her why she's doing this.
Well, in general, any form of fanfiction that involves kidnapping and bondage themes can be a bit dicey in terms of ethics. In the Naruto universe, which is mainly aimed at a younger audience in its original form, such themes are far from the original intention. However, in the realm of fanfiction for an older and more mature audience who understand the fictional and consensual nature of such works in that context, it could be seen as a creative exploration of different scenarios. But it's important to note that it should always stay within the boundaries of legality and respect for the original source material.
In such a fanfiction, Naruto's friends would likely go on a desperate search for him. Sasuke might put aside his pride and team up with the others. They would follow any leads, like tracking the kidnapper's chakra signature if possible.
Well, in that fanfiction, the TMNT being kidnapped by the Shredder would lead to a lot of action. The turtles would surely fight back. They might start by trying to break free from their bindings. Leonardo would probably try to keep his brothers calm and come up with an escape plan. Raphael would be angry and eager to take on the Shredder right away. Donatello would look for any weaknesses in their prison, and Michelangelo might try to use his humor to lighten the mood and also look for an opportunity to escape.
The plot could involve Max being kidnapped by an old enemy from his past. This enemy might want revenge for something Max did before. His friends at CONTROL then have to race against time to find him. They follow a series of clues, like a mysterious note left at the scene of the kidnapping or a strange signal that Max manages to send out.
Max would likely be initially shocked but then quickly start looking for ways to outwit his captors. He'd be making mental notes of everything in the room, like the layout, any possible exits, and what the kidnappers look like.