Maybe there would be a power struggle in the village. With Naruto gone, some might see it as an opportunity to gain more influence. Also, there could be a plot where Naruto's son or a young protege tries to fill his shoes and face the challenges that come with it, like trying to gain the respect of the village in the same way Naruto did.
In this 'everyone thanks naruto is dead fanfiction', characters could have a variety of reactions. For the younger generation, Naruto was a hero. So they might be in tears, feeling like they've lost a role model. The older characters who have seen Naruto grow up would be heartbroken. His death could also lead to political unrest in the village as he was a stabilising force. There would be a general atmosphere of sadness and unease throughout the story.
Perhaps Naruto discovers some hidden powers or abilities that Kunou has inherited from him, which leads to a whole new adventure. They might go on a journey to understand and control these powers together. Also, Naruto could face challenges from the village elders who are not so accepting of Kunou at first.
Another plot development could be that with Sarutobi as his adoptive father, Naruto has access to different mentors. Sarutobi could call in favors from other great ninjas to train Naruto. This would expose Naruto to a wider variety of fighting styles and strategies. Maybe he gets trained by Kakashi earlier, or even has the chance to learn from some of the retired or older ninjas who usually keep to themselves.
One possible plot could be that Naruto is somehow corrupted. Maybe he's been influenced by a powerful dark force or a powerful enemy has tricked him into believing that everyone is a threat to the world he wants to protect. So, he decides to take extreme measures and kill everyone to 'create peace' in his warped sense.
One possibility is that Naruto's friends launch a rescue mission. They would use their unique skills, like Sasuke's Sharingan or Sakura's medical ninjutsu combined with her combat skills, to find and save Naruto.
Well, one possible plot development could be Naruto training even harder to prove himself. After the Chunin Exams, he might seek out new jutsu or ways to improve his skills. Maybe he starts to focus on his control over the Nine - Tails' chakra more intensively.
One possible plot development could be that Naruto's friends in Konoha realize he's missing and start a search mission. They might suspect Kumo immediately due to the history of tensions between the two villages. Meanwhile, in Kumo, Naruto could be held in a secret location. Some in Kumo might want to use him as a bargaining chip against Konoha, while others might see his potential and try to turn him into an asset for Kumo.
In this fanfiction, Itachi might also train Naruto in the ways of the Sharingan. Even though Naruto doesn't have the Sharingan naturally, Itachi could find ways to make Naruto understand the principles behind it, like how to read an opponent's movements more accurately. This could lead to Naruto having an edge in battles against opponents who rely on speed and deception.
Perhaps the plot could involve some sort of magic or curse that is causing Naruto to be in this state. The story might then focus on how the Naruto world's medical ninjas try to figure out what's wrong. They could run all sorts of tests and experiments. And there could be a race against time as Naruto's condition worsens.
One possible plot development could be Naruto focusing on rebuilding Konoha. He might use his newfound influence and power to inspire the villagers and make Konoha stronger than ever. Maybe he starts new training programs for the ninja of the village to better prepare them for future threats.