Naruto's character might become more solitary. The training by Juubi could be intense and isolating, causing him to focus more on his own power and less on his friends. But at the same time, he might also develop a greater sense of responsibility towards the world as he realizes the power he now holds.
If Naruto is trained by Juubi in fanfiction, he could potentially unlock new forms of his power. The Juubi's energy and knowledge might allow Naruto to understand the nature of chakra in a more profound way. He might also develop a different fighting style that combines his own skills with the power of the Juubi, making him a more versatile and unpredictable fighter.
His view of the world would expand. Naruto, who was mainly focused on the ninja world, would now be exposed to the magical world through Merlin. This would make him more open - minded and understanding of different cultures and powers. He may also start to use his newfound knowledge to try and bring peace not just between ninja villages, but also between the ninja world and the magical realm Merlin comes from.
His understanding of the ninja world would expand. He might become more cautious and calculating in battles, as Kaguya's training could expose him to different strategies. Also, he could develop a more solemn side to his personality, considering Kaguya's own complex nature and the heavy knowledge she might share.
His understanding of the ninja way would expand. The Sandaime could share his own experiences and wisdom, making Naruto more in - tune with the deeper meaning of being a ninja. He might also become more confident, knowing he has the backing and training of such an important figure.
His understanding of the Uchiha and the darker side of the ninja world would deepen. Itachi would share his experiences, and Naruto would gain a more nuanced view. This might make him more empathetic towards enemies. Also, his combat skills would diversify. He could incorporate Itachi - like precision and speed into his fighting style, becoming a more well - rounded ninja.
Naruto may become more cunning. Since Anko has her own unique way of doing things, Naruto could pick up on her slyness. He might start to think more like a spy rather than just a straightforward fighter.
His understanding of the ninja world might deepen. Yugao has different experiences compared to his other mentors. So, Naruto could learn about different aspects of the ninja life, like the sacrifices ANBU members make. This would make him more mature in his thinking.
Naruto's character development would be multi - faceted. He would become more strategic in his approach to combat. Yamamoto's battle experience and knowledge would be passed on to Naruto, making him a more well - rounded fighter. Emotionally, he might become more reserved in some ways. Since Yamamoto is not as outwardly emotional as Naruto, Naruto would learn to control his emotions better during battle. However, he would still retain his core values of protecting his friends and the village. This new training would just enhance his ability to do so more effectively.
Naruto would likely become more patient. Kurenai's training methods might force him to slow down and think more carefully, which is different from his usual impulsive self. This could lead to him making better decisions in battles.
Naruto would probably become more disciplined. His impulsive nature might be tempered by Mifune's strict training regime.