Maybe it's because Gaara sees a lot of himself in Naruto. They both had difficult pasts and were kind of loners at first. Gaara wants to protect Naruto from the pain he once endured.
There might be a sense of loyalty that Gaara feels towards Naruto. They may have been through some significant events together in the fanfiction. These experiences made Gaara feel responsible for Naruto's well - being, leading to his overprotective behavior.
It could be that Gaara admires Naruto's spirit. Naruto has this unwavering determination and a kind heart that Gaara respects. So, he doesn't want to see anything bad happen to Naruto and becomes overprotective. He feels that Naruto is someone special who should be kept safe at all costs.
One situation could be in battle. Gaara might shield Naruto from incoming attacks, using his sand powers without hesitation. For example, if an enemy ninja throws a powerful jutsu at Naruto, Gaara quickly forms a sand barrier around him to protect him.
Well, it could change the storyline in many ways. For one, Naruto would have an even stronger support system. Gaara, being overprotective, might prevent Naruto from getting into some of the more dangerous situations he usually jumps into. This could potentially slow down Naruto's growth in terms of combat experience as he'd be shielded from some threats. But on the other hand, it could also give Naruto more emotional stability, which could in turn help him better control his chakra and learn new jutsus faster. Gaara's presence as an overprotective brother could also affect how the other characters interact with Naruto. Some might be more cautious around him because they know Gaara is watching over him like a hawk.
Sakura might be a bit annoyed at first. She's used to Naruto being independent and always charging forward, and Gaara's overprotectiveness could seem like it's getting in the way. Kakashi, on the other hand, would probably be more understanding. He'd see the value in Naruto having someone looking out for him, but he might also try to encourage Gaara to let Naruto grow on his own a bit. Sasuke could have a very negative reaction. He might see it as Gaara trying to steal Naruto away from him in a sense, especially if he has his own unresolved feelings towards Naruto.
One possible scenario in this fanfiction could be that Naruto's sister constantly interferes in his ninja training. She might think the training is too dangerous for him and tries to stop him from taking on challenging missions. For example, when Naruto is about to go on a mission to the Land of Waves, his sister could try to convince the Hokage not to send him, believing that he's not ready yet. This would add a whole new layer of conflict to the story, not just between Naruto and his sister, but also with the village's expectations of Naruto as a ninja.
One aspect of a 'Naruto: Overprotective Kushina' fanfiction could be exploring Kushina's overprotectiveness in Naruto's early life. Maybe she's constantly hovering, fearing for his safety due to her own past traumas. This could lead to some interesting character dynamics, like Naruto feeling smothered at times but also understanding her love.
Well, in the fanfiction world, Minato might be overprotective of fem Naruto because he lost her once. Maybe there was some kind of incident in the past where Naruto was in great danger or even 'died' briefly. This made Minato extremely paranoid about losing her again, so he goes overboard with the protection. He might also be influenced by the fact that as a female in their world, Naruto could face different and perhaps more complex challenges than if she were male, like discrimination or special treatment from certain groups.
Well, Naruto could be depicted as being similar to Gaara in their inner strength. Gaara was always strong on the outside but had a fragile heart. Naruto, in this fanfiction, may share that same duality. Maybe he shows Gaara that having a strong will doesn't mean suppressing emotions. He could be the one to show Gaara that it's okay to let others in, since Naruto is always about making friends and bringing out the best in people.
At first, their relationship might be a bit guarded. Gaara, being used to isolation, might be hesitant to open up to Naruto. But as they face challenges together, like fighting a common enemy, they would start to respect each other's strength. Naruto's positive attitude would gradually break down Gaara's walls, and they would become friends.
For Naruto, he could develop a deeper understanding of the pain that Gaara has been through. This might make him more empathetic towards others who seem hostile at first. He might also learn new combat techniques from observing Gaara's use of sand in the heat of the Chunin Exams battles.
In the Naruto universe, Naruto is a powerful character. Hinata, while strong in her own right, is not as physically dominant as Naruto in many fan interpretations. Naruto's overprotectiveness can show his growth as a character who now has someone he cares deeply about. It also creates drama and tension. For example, when they face enemies together, Naruto's overprotective nature can lead to him making rash decisions or Hinata trying to prove herself despite his protection, which makes for an interesting plot in fanfiction.