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.
There may be some interesting Kushina and Jiraiya fanfictions. You could search on platforms like Archive of Our Own or FanFiction.net. When looking, pay attention to the tags and summaries to find ones that focus on the elements you're interested in, such as their friendship or potential collaborations in the story.
One great fanfic could be about their adventures before Naruto was born. It might explore their relationship dynamics, how they trained together and supported each other. Maybe in this fanfic, Jiraiya tries to convince Tsunade to take on more dangerous missions with him, showing his trust in her abilities.
It could lead to Naruto becoming even stronger and more skilled than in the original story. Jiraiya's training methods might unlock new powers for him.
In many 'Naruto Jiraiya fanfiction' works, the relationship is explored through flashbacks. For example, Naruto might recall the times he spent training with Jiraiya, like how Jiraiya taught him the Rasengan. This helps to show the bond they had, with Jiraiya being a father figure to Naruto.
One popular theme is his relationship with Naruto. Many fanfics explore how he mentored Naruto, the lessons he taught him, and the bond they shared. Another theme is his travels. Since Jiraiya was a wanderer, fanfics often detail his adventures in different lands, the people he met, and the new ninjutsu he discovered.
Jiraiya's story concludes in Shippuden. It's a heartbreaking part of the storyline that leaves a lasting impression. His death sets the stage for many important events and motivations for the other characters.
One possible reason could be that Naruto might feel Jiraiya is being too overbearing in his training methods. In some fanfictions, Jiraiya might push Naruto too hard without considering his emotional state, leading to Naruto snapping.