Naruto might initially be shocked and angry. He has always considered the Kyuubi as an enemy within him, and now being kidnapped by it is the worst - case scenario for him. He could try to fight back immediately, using whatever little chakra he can muster without relying on the Kyuubi's power.
He could also try to reason with the Kyuubi. Naruto is known for his ability to see the good in people (or in this case, the tailed beast). He might ask the Kyuubi why it's doing this and try to find a peaceful solution. This could lead to a deeper understanding between them, and maybe Naruto could even convince the Kyuubi to let him go or work together against a common threat.
Naruto might initially be shocked and angry. He has a strong sense of justice and being kidnapped goes against everything he stands for. He would likely try to fight back immediately, using his basic ninja skills and his determination. For example, he could try to use his Shadow Clone Jutsu to create distractions and escape.
Once he realizes that Gaara is serious about the kidnapping, Naruto would start to plan his escape. He would use his ninja skills and his quick thinking. Naruto has a lot of experience in getting out of tough situations. He would look for any weaknesses in Gaara's defenses or in the place where he is being held. And while he's planning his escape, he would still be trying to reason with Gaara, hoping to resolve the situation without having to fight his friend.
At first, Naruto might be extremely shocked. He trusts Sakura as a teammate and friend, so being kidnapped by her would be completely unexpected. He would likely try to talk to her, asking her why she's doing this.
Naruto would probably be very confused at first. He trusts Sasuke, even if it's a Fem Sasuke in this fanfiction, and he wouldn't expect to be kidnapped by her. So, his initial reaction might be to try and talk to her, asking her why she's doing this.
Naruto would probably be angry at first. He's always been a free - spirited person, and being kidnapped by Sasuke, his friend - turned - rival, would surely make him mad. He'd likely try to fight back immediately, using his ninja skills and his never - give - up attitude.
He might be shocked at first. Naruto has always had a complex relationship with the Kyuubi, so finding out his mother is somehow related to it would turn his world upside down. He would probably have a million questions running through his head and would need time to process such a huge revelation.
She would probably be very angry at first. Naruto is a headstrong character, and being kidnapped against her will would make her furious. She'd likely try to fight back immediately, using whatever skills she has at her disposal.
He might be initially confused. Naruto is used to dealing with all kinds of opponents and situations, but a yandere Kyuubi would be a new and strange thing for him. He could try to reason with her at first.
Well, in certain fanfic concepts, Naruto could control Kyuubi chakra with the help of unique jutsu or seals. For example, he might discover a new sealing technique that allows him to better manage the flow of the Kyuubi's power. This new seal could work in harmony with his own chakra system, enabling him to draw on the Kyuubi's strength without being overwhelmed. Also, some fanfictions might suggest that his strong emotional bonds, like his friendship with his comrades, give him the extra mental fortitude to control such a powerful chakra source.
The fear might be manifested in the Kyuubi's attempts to negotiate with Naruto rather than fight. In fanfiction, the Kyuubi could offer Naruto things or make promises in order to avoid a situation where Naruto uses his power against it. This shows that the Kyuubi is aware of Naruto's strength and is scared of the consequences of going against him.