One way this could be developed is if Naruto is somehow mind - controlled. For example, an enemy uses a powerful genjutsu on Naruto, making him lose his sense of self and see the Third Hokage as a threat to the village instead of a protector. Then, in his confused state, he attacks and kills the Third Hokage. This would create a huge moral and emotional conflict within the story, not only for Naruto when he comes to his senses but also for the entire village.
Perhaps in a dark fanfiction, Naruto discovers a dark secret about the Third Hokage that he believes makes him unworthy of leading. This secret could be something related to the Uchiha clan's massacre. Naruto, in his idealistic and sometimes headstrong way, decides to take matters into his own hands and challenges the Third Hokage to a fight, which ends in the Hokage's death. This would then lead to Naruto being seen as a villain by some and a hero by others who believe in his cause.
It could be a story where Naruto is tricked by a powerful antagonist. The antagonist convinces Naruto that the Third Hokage is planning to sacrifice him for the greater good of the village. Angry and feeling betrayed, Naruto attacks the Third Hokage without fully understanding the situation. After the killing, Naruto realizes he has been deceived, but it's too late. This sets off a chain of events where Naruto has to deal with the guilt and also face the consequences from the village.
In some fanfictions, there could be an alternate reality or a time - travel plot involved. Maybe Kakashi from the future accidentally goes back in time and in the chaos of trying to fix something, he ends up killing Naruto. This would completely change the course of the Naruto - verse. Characters like Hinata, who had feelings for Naruto, would be heartbroken. And the Akatsuki might take advantage of the situation, seeing the Hidden Leaf Village in a state of disarray without Naruto as their potential Jinchuriki and future hope.
One possible plot could be Naruto dealing with the post - war reconstruction. He might focus on rebuilding the village, strengthening relations with other villages, and also mentoring the new generation of ninjas. For example, he could start new training programs inspired by his own experiences.
In a fanfiction, if Naruto and Itachi were both involved in the Hokage scenario, Itachi could be resurrected through some means and Naruto, already a respected figure in the village, would propose Itachi as a candidate for Hokage. Itachi would initially be hesitant but Naruto's persuasion and the villagers' need for a different kind of leadership would make him accept. His time as Hokage would involve him training a new generation of shinobi in not just combat but also in understanding the importance of sacrifice and loyalty, with Naruto as his right - hand man, guiding him on how to interact with the more jovial and carefree side of the village life.
In this fanfiction, Naruto could be given a special mission by an unknown entity to save the Third Hokage. This mission might push Naruto to his limits and force him to unlock hidden potential within himself. Along the way, he might face challenges that test his loyalty and friendship.
In a Naruto kills Kiba fanfiction, one way it could be developed is through a misunderstanding. Maybe Kiba is framed for a crime against the village that Naruto believes wholeheartedly. Naruto, in his overzealous sense of justice, might attack Kiba without fully understanding the situation. However, this goes against Naruto's character in the original series, so it would require a significant deviation from the canon.
One way it could be developed is through extreme despair. Maybe Naruto fails to protect the village from a new and overwhelming threat. He blames himself so much that he starts to think his death would be a solution. For example, if all his friends were killed in the battle and he felt powerless to stop it, he might sink into deep depression and consider suicide as a way to end his pain.
Maybe Naruto is framed by a powerful enemy within Konoha. False accusations are made against him, and instead of getting a fair trial, he is hunted down. This injustice could make him turn his back on the village that he once loved and swore to protect.
One possible plot twist could be that Sadime Hokage is secretly from an enemy village but has been undercover in Konoha for years. She falls in love with Naruto during her time there and has to choose between her loyalty to her original village and her newfound feelings. Another could be that Naruto discovers a hidden power within Sadime that is related to an ancient prophecy, and they must work together to prevent a great disaster.
One possible plot could be Naruto and Minato having a deep conversation about Naruto's journey as Hokage. Minato might share his own experiences and offer advice on handling the tough decisions. They could also talk about family, like how Naruto is raising his own kids and how Minato wished he could have been there for Naruto's upbringing.
One possible plot could be Naruto Namikaze facing new threats to the Hidden Leaf. He might have to deal with a powerful enemy from a neighboring village who is after the village's secrets. He uses his unique skills and leadership to rally the shinobi of the Leaf and come up with new strategies to protect the village.