One idea could be that Sakura has been manipulated by an outside force, like an enemy from another village who has planted false memories in her head about Naruto being a threat. This causes her to take extreme actions against him. Or maybe there's a complex love triangle gone horribly wrong where Sakura's jealousy towards Naruto's relationship with someone else drives her to this extreme act.
Well, perhaps in this fanfiction, there is a power struggle within the village. Sakura, in her pursuit of power or influenced by a power - hungry villain, sees Naruto as an obstacle and decides to kill him. It could also be related to some prophecies or ancient grudges that are wrongly placed on Naruto in the context of the fan - created story.
In such a fanfiction, one possible storyline could be that Sakura is under some dark magic or mind control which makes her turn against Naruto. Another could be a huge misunderstanding where she believes Naruto has done something unforgivable to her or their friends.
Perhaps there is a situation where Sakura is trying to protect Naruto from a dangerous attack, but due to some unforeseen circumstances, like a misdirected healing jutsu turning into a harmful one, she ends up killing him. It could then lead to a story of guilt, revenge, and the search for a way to bring Naruto back.
In such a fanfiction, one possible storyline could be that Naruto is somehow mind - controlled and attacks Konohamaru without his own free will. Another could be a situation where there is a huge misunderstanding, like Konohamaru is framed for a serious crime against the village and Naruto, in his overzealous sense of justice, takes extreme action. However, this goes completely against the character development and the bond they have in the original series.
One possible reason could be a sudden and extreme corruption of Naruto's character. Maybe he is influenced by some dark and powerful force that makes him turn against his friends. Another reason might be a misinterpretation of a prophecy or some kind of mind - control situation.
A storyline could involve a time - travel element. Naruto, Sasuke, and Sakura are sent back in time and find themselves in a situation where they have to get married to change the future. They start off as reluctant partners but as they spend more time together in the past, they develop real feelings for each other. They also have to hide their relationship from their past selves and other characters while trying to figure out how to change the future.
It could be due to a dark influence. Suppose she was under the influence of some dark magic or an evil force that made her lose her true self and turned her against Naruto. This could lead to her almost killing him in the fanfiction.
One possible storyline could be that Naruto is corrupted by a powerful dark force. This force twists his mind, making him see his friends and allies as threats, and he starts killing them one by one. Another could be in a post - apocalyptic Naruto world where resources are scarce, and Naruto has to kill to protect his own group from others who are desperate for food and water.
One possible storyline could be Naruto is depressed because he feels unappreciated in the village despite all his efforts. Sakura, realizing his state, tries to cheer him up by spending more time with him. They start training together and Sakura slowly helps Naruto see his own worth through her belief in him.
One possible storyline could be that Dark Naruto, with his edgier and more troubled persona, saves Sakura from a dangerous situation. This experience makes Sakura see him in a new light and she starts to develop feelings for him. As they spend more time together, Dark Naruto slowly opens up to her about his inner turmoil.
One possible storyline could be that Sakura witnesses Naruto getting seriously injured while protecting the village. She cries out of fear of losing him and blames herself for not being strong enough to protect him. Another could be Naruto making a sacrifice for a greater good, like leaving the village forever, and Sakura cries as she realizes she might never see him again. Maybe Naruto gets into a relationship with someone else, and Sakura, who has hidden feelings for him, cries in heartbreak.
A storyline could be that there is a mysterious illness spreading in the village. Sakura and Sarada work together to find a cure, while Naruto and Boruto protect the village from any threats that might take advantage of the situation. It could show the passing on of skills and the importance of teamwork between the generations.