Maybe Kakashi is preoccupied with other important missions. He is a highly - skilled and often - needed ninja. There could be some top - secret missions that require his full attention, leaving him no time to train Naruto properly.
Naruto might also try to find alternative ways to gain strength. He could explore the forest around the village to find new training areas or discover new chakra - related phenomena. He has a curious nature, and this could lead him to stumble upon something that gives him an edge in his training, like a hidden hot spring that has special chakra - enhancing properties.
In the fanfic, Kakashi might neglect Naruto's training due to a variety of reasons. He could be preoccupied with his own research or a secret mission that demands his full attention. There could also be a misunderstanding between him and Naruto. Maybe Naruto has done something that Kakashi misinterprets, causing him to distance himself from Naruto's training. Additionally, the fanfic could introduce new characters or plot elements that draw Kakashi's focus away from Naruto. For example, a new threat to the village that Kakashi feels he must handle alone, thus neglecting his duties as Naruto's trainer.
Perhaps he's been influenced by someone who gives him bad advice. For example, if someone tells him that natural talent is enough and training is overrated. Also, he could be dealing with some personal problems, like a conflict within his family or among his friends that takes up all his time and mental energy, causing him to neglect training.
Well, Kakashi might start by spending more time with Naruto. He could train Naruto more intensively, like teaching him new jutsu. Maybe he also shares his own experiences to give Naruto some guidance and motivation.
It could also have caused a rift between her and Kakashi. Sakura might start to resent him for not believing in her or giving her the proper training. This could affect the team dynamic. Maybe she would start to distance herself from the team and try to find her own path, which could lead to some interesting plot developments in the fanfiction. For instance, she could end up joining a different ninja squad temporarily to get the training she needs.
Another possibility is that Sakura would feel really down at first. But then, inspired by her love for Sasuke or her desire to protect her friends, she would pull herself together. She could approach other more approachable senior ninjas for advice on how to train without Kakashi's guidance. For example, she might go to Shizune, who could give her some basic medical - ninjutsu training tips that she could build on herself. And she could also practice her physical strength training on her own, like doing extra push - ups and running drills in the forest.
Well, it could make him more desperate to catch up. He might become more self - doubting at first. But then, as he realizes his mistake, he could develop a stronger sense of determination to overcome his lack of training. For example, he might start training in more unorthodox ways to make up for lost time.
In many Naruto fanfictions about Kakashi training Naruto, Kakashi might push Naruto to new limits. He could focus on Naruto's Rasengan training, making it more powerful or teaching him new variations. For example, Kakashi might introduce elements to the Rasengan, like wind or lightning, to enhance its destructive power. This kind of training would not only strengthen Naruto physically but also help him understand chakra better.
One possible reason could be that Kakashi might think Naruto is not ready yet. Maybe Naruto hasn't mastered some basic skills that are prerequisites for the more advanced training Kakashi has in mind. Another reason could be that Kakashi is worried about Naruto's recklessness. Naruto has a tendency to rush into things without thinking, and Kakashi might fear that this could lead to Naruto getting seriously injured during the training.