His character could become more mature. Since Kyuubi has a lot of knowledge and experience, Naruto would learn from it. He would be less impulsive and think more before acting. Their friendship would also make Naruto more understanding of the darker aspects of life, as Kyuubi has seen a lot of pain and destruction. This new understanding would shape him into a more well - rounded and wiser ninja.
His friends might be a bit more cautious around him at first. After all, the Kyuubi is a very powerful and somewhat feared entity. But as they see that Naruto is still himself, they gradually become more accepting. For example, Sasuke might initially be on guard but then realize Naruto is still his friend.
Naruto's caring changes their relationship in a positive way. At first, the Kyuubi saw Naruto as just a vessel. But as Naruto shows care, the Kyuubi starts to see him as an equal. For instance, it might start to communicate more openly with Naruto, sharing its knowledge of the ninja world.
In this fanfiction, their relationship becomes more of a partnership. Instead of Naruto just using the Kyuubi's power, they work together as brothers. Naruto might start to understand the Kyuubi's feelings and motives better.
He might become more aggressive. Because he looks like Kyuubi, he may start to act more like the powerful and sometimes wild - tempered fox. His usual friendly and sometimes goofy nature could be overshadowed by a more serious and intimidating demeanor.
Naruto may become more confident. Having the Kyuubi body gives him a new level of power, which could boost his self - assurance in battles and in his interactions with others.
Their relationship would become more mature and responsible. With a child to take care of, they would have to communicate more effectively. Naruto, who is often impulsive, might become more cautious for the sake of the child. Hinata, already a calm and loving person, would be the stable force in their family. They would rely on each other more, and their bond would strengthen as they share the joys and challenges of raising a child.
If Naruto and the Kyuubi switch places, his friends might be initially very confused. They are used to Naruto's normal behavior. If the Kyuubi is in Naruto's body, it might be more aggressive or act in ways that seem out of character. His friends would have to figure out what's going on. But if Naruto is in the Kyuubi's place, his friends might start to worry about him more, not knowing what he's experiencing inside the seal.
In some fanfictions, Naruto might start by trying to understand the Kyuubi's pain. He could use his own experiences of being an outcast in the village to empathize. As he shows this understanding, the Kyuubi begins to see him as different from the other humans who just fear it. They might start having conversations in Naruto's mindscape, gradually building a bond of mutual respect.
His view of the world would expand greatly. If Naruto is a Xenophage in this fanfic, he would be exposed to different types of entities and powers that are not native to his world. This would make him more open - minded and curious. He would start to question the nature of his own world and the existence of other dimensions. His character would develop from a simple - minded, if brave, ninja to a more complex and philosophical figure, constantly seeking to understand the greater mysteries of the universe while still maintaining his core values of protecting his friends and village.
Their relationship could start with Kurenai being cautious around Naruto as he is now the Kyuubi. But as she sees his struggle to control the power and his good intentions, she warms up to him. She might become a mentor - like figure, guiding him on how to use his new abilities for the greater good. And Naruto would respect her for her knowledge and kindness, leading to a strong bond of trust between them.