On Gaara's side, he would have to live with the guilt. He has come a long way from being a cold - hearted killer and killing Naruto would be a major setback for his character development. His village might also face the wrath of Konoha and other allies of Naruto. The relationship between the two villages that Naruto worked so hard to build would be in tatters.
The most immediate consequence would be the reaction from Naruto's friends. Sasuke, for example, would likely go on a quest for revenge. He has a deep bond with Naruto and would not let his death go unpunished. Sakura would also be devastated and might lose faith in the idea of peace between the villages.
The most obvious consequence would be the extreme grief among Naruto's friends like Sasuke, Sakura, and Kakashi. They would be devastated and likely seek revenge. The village would also be in chaos as Naruto was seen as a hero - in - the - making. It would completely change the future of the village.
He might start to compare the fanfiction world too much with the real Naruto story, which could lead to some confusion. For example, if a fanfiction has a completely different view of a character's personality, he may struggle to separate it from the original.
The Akatsuki might take advantage of the situation. With Naruto gone, there's no one to oppose them as strongly. They could start making bolder moves, attacking villages more openly. The other villages might also see Konoha as a threat since one of their own teams killed their most powerful ninja. This could lead to all - out wars between the villages, changing the entire political and power structure of the fanfiction's ninja world.
In a possible fanfiction scenario where Naruto is killed by Gaara, it could be due to a breakdown in their understanding. Maybe a powerful and dark force has corrupted Gaara's mind, making him see Naruto as an enemy when Naruto tries to help. Gaara's sand powers are extremely strong and if he goes on a rampage without realizing who Naruto really is, he could end up killing him.
One possible consequence could be a huge shift in the power dynamics among the ninja villages. Since Naruto was seen as a potential strong force, his death might make Konoha more vulnerable. Also, his friends like Sasuke and Sakura would be deeply affected. Sasuke might be driven further into his quest for power in a more reckless way out of revenge or a sense of loss. And Sakura would likely be devastated, perhaps changing her path from a healer to someone more focused on vengeance as well.
Well, it could be really interesting. Naruto and Gaara are both complex characters. In such a fanfiction, they might grow up as brothers in a way. They could train together, share their insecurities. Naruto could help Gaara deal with his inner demons earlier, and Gaara could be a more stable support for Naruto when he faces difficulties in the village. Maybe they'd even create new jutsus together.
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.
Hinata would be devastated. She has always had deep feelings for Naruto. She might lose all hope and become a shell of her former self. Also, Kakashi would feel a great sense of guilt. He was Naruto's teacher and protector in a way. He would probably question his own abilities and actions that led to this situation. And for the village as a whole, it would soon realize the mistake they made when they face new threats without Naruto to protect them.
Naruto would likely show Gaara that the village can be a place of acceptance. He could introduce Gaara to the villagers, starting with the kids. The kids' innocent acceptance of Gaara would be a big step in changing his view. For example, they could play games together in the village square.
Well, in fanfiction, if Naruto and Gaara joined Akatsuki, it would be a total chaos for the ninja world. Akatsuki's goals would likely be completely derailed. Naruto is all about friendship and protecting the village, and Gaara has also turned to the side of protecting his people. Their values would clash with Akatsuki's more malevolent intentions. Maybe Naruto would try to reform Akatsuki from the inside, and Gaara would be there to back him up with his powerful sand abilities.