Another reason could be that Jiraiya has some doubts about Naruto's readiness or potential. He might think that Naruto is not yet at the level where he can fully benefit from Jiraiya's training. For example, Naruto may lack some basic skills or knowledge that Jiraiya believes are necessary prerequisites for his more advanced training.
One possible reason could be that in this fanfiction, Jiraiya might be preoccupied with other important matters. Maybe he has a secret mission that demands his full attention and he simply doesn't have the time to train Naruto. Another reason could be that there is some sort of conflict or misunderstanding between them that prevents Jiraiya from taking Naruto under his wing. For example, Naruto might have unknowingly offended Jiraiya in some way, or there could be a prophecy or external force that is keeping them apart for the time being.
Jiraiya could also train Naruto seriously in fanfiction through intense physical conditioning. He might make Naruto run long distances, climb mountains, or swim across large bodies of water. This would build Naruto's stamina and strength, which are crucial in battle. Additionally, Jiraiya could teach Naruto advanced ninjutsu techniques, like new ways to use his Rasengan or how to combine different elemental jutsus.
Perhaps Jiraiya has some personal issues or inner conflicts. He might be dealing with his own past traumas or demons that prevent him from taking on the role of Naruto's trainer. For example, he could be haunted by the failures in his previous relationships or battles, and he feels unfit to train Naruto until he sorts out his own problems.
Naruto might be initially very disappointed. He has always looked up to Jiraiya and expected to be trained by him. So, when faced with the refusal, he could be heartbroken and feel like he has lost a great opportunity.
In some fanfictions, Minato might start by teaching Naruto advanced chakra control techniques. This could include things like walking on water or up trees more proficiently, which are basic yet important skills for the Chunin Exams. He may also introduce Naruto to some unique jutsu that he, Minato, was known for, like the Rasengan, but with a new twist or improvement.
In fanfiction, Minato might use shadow clones to spar with Naruto simultaneously from different angles, enhancing Naruto's combat reflexes. For example, the clones could attack Naruto in various ways, forcing him to quickly adapt and find counter - attacks.
One possible plotline could be that Minato and Kushina focus on teaching Naruto advanced chakra control. Since Minato was known for his Flying Thunder God Technique which required precise chakra control, he could pass on those skills. Kushina, with her strong chakra, might teach Naruto how to better harness his own Uzumaki chakra reserves. For example, they could start with basic exercises like tree - walking and water - walking, but with a twist. Minato could show Naruto how to use his chakra in a more efficient and strategic way during these exercises, preparing him for more complex jutsu later.
In the fanfiction, Jiraiya's training methods for Naruto are comprehensive. Firstly, there's the physical aspect. Jiraiya could be making Naruto do things like carrying heavy rocks for long distances to build up his endurance. For ninjutsu, he'd be teaching Naruto not just new techniques but also how to innovate and combine existing ones. He might also take Naruto on dangerous missions where Naruto has to learn on the fly. Jiraiya would also focus on Naruto's mental strength, teaching him how to stay calm under pressure and not let emotions cloud his judgment during battles.
Minato, being a highly intelligent ninja, would have a more cerebral approach to training Naruto. He might start with theory, explaining the principles behind various jutsu and techniques. He would then gradually move on to practical applications. His training would also involve a lot of stealth and misdirection elements, as these were crucial to his own fighting style. Kushina, with her fiery personality, would have a more passionate training style. She would push Naruto to his limits physically, making him do intense chakra - building exercises. And she would also share stories from her own training days to inspire Naruto.