There are several ways in fanfiction. Firstly, the Kyuubi's chakra can distort Naruto's normal appearance. His skin might take on a reddish tint, similar to the color of the Kyuubi. His teeth can become sharper as well. Secondly, the Kyuubi's instincts can take over Naruto's decision - making process. He may start to hunt or fight in a more brutal way than he usually would. This new - found brutality makes him seem less like a normal ninja and more like a demon. Thirdly, the Kyuubi's presence in Naruto can cause a sense of unease among other characters. They can sense the powerful and somewhat evil energy within Naruto, which leads them to think of him as a demon.
One way is through Naruto's appearance. The Kyuubi's power might make Naruto's hair look wilder, like the Kyuubi's fur. His face could also get some markings similar to the Kyuubi. Another way is his strength. When Naruto uses the Kyuubi's power, he might be so strong that it scares people and they start to see him as a demon. Also, the Kyuubi's negative emotions can influence Naruto, making him seem cold and cruel at times.
In fanfiction, the Kyuubi can affect Naruto in multiple ways to give him a demonic look. Physically, the Kyuubi's chakra can cause Naruto's body to heat up and steam to come out of him, which looks very inhuman. His voice can also change, becoming deeper and more growl - like. Emotionally, the Kyuubi can make Naruto more territorial. He may start to defend his space aggressively, like a wild animal. This change in behavior makes others view him as a demon. Moreover, the Kyuubi's power can make Naruto's eyes glow in a very eerie way, adding to the demonic appearance.
The Kyuubi is a nine - tailed fox with a lot of dark and wild energy. In fanfiction, when it comes to Naruto, this energy can manifest in various ways that make him seem like a demon. For one thing, the Kyuubi's chakra can cause Naruto to have an aura that is both menacing and inhumane. His movements might become more animal - like, as if he's being controlled by the primal instincts of the Kyuubi. Additionally, his speech and the way he interacts with others can change. He may become more solitary and less empathetic, which are traits often associated with demons in fictional stories.
One way is through enhanced emotional bonds. If Naruto experiences a very strong emotion like extreme love or a sense of justice, it might trigger a stronger connection to the Kyuubi and thus more power. Another way could be through new types of seals. Maybe a fanfic writer creates a seal that not only contains the Kyuubi but also channels its power more effectively to Naruto.
One common way is through power boosts. The Kyuubi's chakra gives Naruto the strength to take on tougher opponents.
Sasuke often appears. Since he is Naruto's rival and friend, his relationship with Naruto might be affected by the Kyuubi's influence on Naruto. Kakashi could also be there, as Naruto's teacher, he might notice the changes in Naruto due to the Kyuubi's new role in his life.
One role is to enhance Naruto's combat abilities. It can give him an edge in battles, like allowing for more unpredictable attacks. For example, it could make his shadow clones more versatile.
One consequence could be that Naruto grows up with an even stronger connection to the Kyuubi's power from a very young age. This might make him a much more powerful ninja earlier on in his life.
One way is through his Jinchuriki status. The Nine - Tailed Fox inside him has a primal connection to nature in some fanfictions. The fox's chakra, which Naruto can access, is linked to the natural forces of destruction and creation. Another way is his friendship with animals. Naruto is sometimes shown befriending forest creatures, which shows his harmonious connection with nature.
There are fanfictions where Naruto teams up with other powerful characters like Jiraiya. Together, they come up with a plan to trap Orochimaru and then Naruto delivers the final blow. Naruto might use his Sage Mode skills, if he has them in that particular fanfiction, in combination with Jiraiya's knowledge and power to outwit and defeat Orochimaru.
One way Ino helps is by being a source of emotional support. Her friendship with characters like Sakura can be a stabilizing force. In some fanfictions, she might offer advice on relationships or personal growth.
One common way is by sharing its chakra. Naruto can draw on this extra chakra to increase his strength and speed. Another way is through its knowledge. Kyuubi has a long memory and can pass on useful information about the ninja world.