It could be Orochimaru. Since Orochimaru has a long - standing feud with Jiraiya and is always up to no good. If Naruto ditches Jiraiya, Orochimaru might see this as an opportunity to manipulate Naruto. He could try to convince Naruto that Jiraiya was holding him back and that he can offer Naruto more power, all while having his own evil plans for Naruto.
One possible plot development is that when Zero's identity is revealed, it could spark a civil war among different factions. Supporters of the original regime might see this as an opportunity to regain power, while others might try to use the situation to further their own agendas. Also, the character relationships would be greatly affected. Characters like Suzaku might have to re - evaluate their stance towards Zero.
The training makes Naruto more confident in his abilities. Jiraiya constantly challenges Naruto and as Naruto overcomes these challenges, he realizes his own strength. He starts to believe in himself more, which is evident in the way he faces stronger opponents without hesitation later on. Also, Jiraiya's teachings about the ninja way and the importance of protecting those you love make Naruto more determined and focused on his goals.
Jiraiya's training in the fanfiction might focus on Naruto's inner strength as well. He could help Naruto better understand and control the Nine - Tails' power. This new - found control would give Naruto a sense of calm and authority. His character would shift from being just a loud - mouthed underdog to a more respected and powerful ninja. Naruto would also learn about loyalty and sacrifice from Jiraiya, which would shape his values.
In this fanfiction, their relationship would be transformed. They would be like a married couple in a way, but without the formalities. Jiraiya would probably tone down his womanizing ways as he has a family to think about now. Tsunade would be more open and less prickly around Jiraiya. They would bicker less and cooperate more. Their relationship would be centered around Naruto, and as he grows, they would grow together as a family unit, with their bond getting stronger over time.
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.
Their relationship would be very strong. Jiraiya would see Naruto as not just a student, but also as a connection to Minato. He would be strict but also very affectionate. Naruto would look up to Jiraiya as a father figure, since he never really had one. They would share many adventures together, with Jiraiya teaching Naruto about life, love, and ninjutsu.
It can create a sense of growth for Naruto. Without Jiraiya by his side, he has to rely more on his own instincts and the skills he has already acquired. This can lead to new character development as he faces challenges alone.
When Zero's identity is revealed in the fanfiction, it can completely derail the existing story arc and send it in a new direction. For instance, if his identity was previously a mystery that held together a certain power structure, its revelation could cause that structure to collapse. This would then force the characters to adapt to new circumstances. Allies may become enemies and vice versa. The story may also shift from a more strategic, large - scale conflict to a more personal, character - driven struggle as the true identity of Zero brings out hidden motives and emotions among the other characters. This new direction can add depth and unpredictability to the overall story arc.
Naruto is devastated. He feels a huge void in his heart. Jiraiya was the one who believed in him from the start, and his death makes Naruto question a lot of things. He might even start to doubt his own strength for a while.