A new character could be an old hermit who lives in a hidden cave in the mountains. This hermit has mastered a unique form of chakra control that allows him to manipulate the elements in ways not seen before. He takes an interest in Team 7 and decides to train them. He teaches Naruto how to combine his wind chakra with the earth beneath him to create powerful tornado - like attacks. For Sasuke, he shows how to infuse his fire chakra with lightning to make it more potent. And for Sakura, he helps her develop a new form of medical ninjutsu that can heal internal injuries more quickly.
There could be a foreign ninja from a far - off land. This ninja has a different fighting style that focuses on using sound waves as a weapon. He joins Team 7's training. He trains Naruto to use his voice to enhance his jutsu, like making his Rasengan louder and more powerful. Sasuke learns how to use sound to disrupt his opponents' attacks. And Sakura discovers that she can use sound waves to detect internal injuries more accurately in her medical ninjutsu practice.
The Hokage, like Tsunade or Kakashi, could be the ones training Naruto. They know Naruto well and have a lot of knowledge and skills to pass on.
The characters might include some lesser - known characters from the Naruto series who get a chance to shine. For instance, Rock Lee could be part of the crazy team, teaching his unique taijutsu training methods to the others. And then there could be a character who is a foreign ninja, bringing in new techniques and a different perspective to the training.
One possible interesting plot could be that Team 7 is trained by a new sensei who has a very different style from Kakashi. This new sensei focuses more on survival skills in extreme terrains. So, Naruto, Sasuke, and Sakura have to learn how to build shelters in deserts, jungles, and snowy mountains. They also learn to hunt for food and purify water in the wild. This new training makes them stronger both physically and mentally, and they develop new jutsu based on their experiences in these extreme conditions.
The plot could involve a group of underdog ninjas forming a crazy team. They might start with really wacky and unorthodox training methods, like training on a constantly shifting terrain made by a jutsu. Their goal could be to master a unique and powerful ninja skill that no one has ever seen before in the Naruto universe.
A new Akatsuki member, a young and powerful ninja who has a personal vendetta against Naruto. Their clashes could add a lot of drama and action to the fanfic.
There could be a group of orphans who have banded together and developed their own unique style of ninjutsu out of necessity. These orphans could add a new dimension to the story as they struggle to survive in a world full of powerful ninjas while also trying to find their place in it.
There could be new antagonists created specifically for this fanfic. Maybe some dark forces that were sealed away by Asura long ago are awakened. They would oppose Naruto because they see him as a threat to their resurrection or their evil plans.
It could be some rogue shinobi who are after Pakura's knowledge. Since she's training Naruto, they might see it as an opportunity to get to both of them and steal their techniques. Maybe they were once her enemies or just power - hungry individuals.
Maybe it's a member of a long - lost ninja clan. This clan member could have some special skills and knowledge that they want to pass on to Naruto. They choose to train him in secret to protect their clan's secrets from falling into the wrong hands.
Well, Goku's training is intense. It might involve extreme physical conditioning like his gravity training. Naruto could be pushed to his limits in terms of strength and speed. He'd probably learn about ki control, which is different from chakra but could enhance his abilities. Goku might also teach Naruto about the importance of a strong mental state during battle, something Naruto already has a bit of but could be refined.