In some fanfictions, it could be a misunderstanding between them. Kakashi might misinterpret Naruto's actions as being a threat to the village. For instance, if Naruto discovers a new and powerful jutsu that has some unknown side - effects. Kakashi, in his role as a protector of the village, might try to stop Naruto from using it, and in the process, accidentally hurts him. This would then lead to a lot of emotional turmoil between the two characters.
Perhaps in the fanfiction, Kakashi is influenced by a dark power. This power corrupts his mind and makes him turn on Naruto. It could be related to some ancient curse or a new enemy's ability that targets Kakashi's mental state. Naruto, being the target, would then be at the mercy of Kakashi's attacks, creating a lot of drama and conflict in the story.
Perhaps there's a mission where Kakashi and Sasuke are on opposite sides. Kakashi is following the orders of the village, and Sasuke is following his own path for revenge. In a confrontation, Kakashi uses his Sharingan - based techniques against Sasuke. Sasuke, not fully prepared to face Kakashi at that level, gets hurt. This would add more complexity to their relationship as teacher and student.
One possible storyline could be that Anakin, under the influence of the dark side, accidentally uses too much force during a training session with Ahsoka, physically hurting her. This could lead to a rift in their relationship as Ahsoka struggles to understand what happened and Anakin feels guilty.
One possible storyline could be a misunderstanding. Maybe Nami thinks Luffy has made a deal that endangers the crew without realizing his true intentions. So, in her anger and worry, she accidentally hurts him while trying to stop him from doing something she believes is wrong.
One possible storyline could be that the Avengers are under some form of mind control. Maybe a powerful villain has manipulated them into believing Tony is a threat to the world. So, they start to target him, causing both physical and emotional harm. For example, they might break into his workshop and destroy his latest inventions, which are not only his creations but also his passion.
In some fanfictions, Sasuke might be in a situation where he has to choose between his goals and Sakura. His choice could end up hurting her. For instance, he decides to go on a very dangerous mission alone, knowing that Sakura is deeply in love with him and would be worried sick. His disregard for her feelings in this case is a form of emotional hurt. Also, there could be a scenario where Sasuke is forced to fight against Sakura in a misunderstanding, and his superior skills end up causing her serious injuries.
One possible storyline could be Kakashi taking young Sakura under his wing for special training. He might notice her potential beyond just her medical skills and start teaching her advanced ninjutsu techniques. This could lead to a strong bond between them as mentor and student.
Well, it could be a situation where Hinata is trying to protect someone else from Naruto, perhaps believing he is a threat at that moment due to some false information. She might then end up hurting him while trying to fend him off. Or, in a darker fanfiction, there could be an alternate universe where Hinata has turned evil and deliberately targets Naruto to cause him harm.
The fanfiction could explore how their relationship changes over time. At first, Naruto could be devastated by Kakashi's actions. But as the story progresses, Kakashi could realize his mistake and try to make amends. This would create a journey of forgiveness and rebuilding their relationship. They might have to work through a lot of emotional baggage and trust issues.
One possible storyline could be that Naruto receives Kakashi's Sharingan through some sort of magical or experimental transfer. This new power could make Naruto even more formidable in battle. He might start to see the world in a different way, with the Sharingan's abilities to copy jutsu and predict movements. This could lead to new training regimens as he tries to master the Sharingan's full potential while still relying on his own Uzumaki powers like the Nine - Tails chakra.
One interesting storyline could be Kakashi taking on a more fatherly role towards baby Naruto. He could teach Naruto some basic ninja skills from a very young age, like how to throw a kunai properly. This would create a strong bond between them early on.