Well, it could be about the fox brother having special powers. Maybe he can communicate with Naruto in a unique way, like through telepathy. They might go on adventures together, facing off against enemies that Naruto couldn't handle alone. The fox brother could also have a connection to Naruto's own inner fox spirit, and they could work together to control that power better.
It could be a powerful ninja who wants to capture the fox brother for his own purposes. Maybe he believes that the fox brother's powers can be used to take over the ninja world. This antagonist might be from a rival village or a secret organization within Naruto's own village.
One great fanfiction is 'The Fox - Eyed Naruto' on FanFiction.net. It really delves into how Naruto's fox - eyed appearance changes the way people perceive him in the village. The author does an amazing job of integrating this new physical trait into the existing Naruto universe storyline.
The older brother in the fanfiction might be a character with a tragic past. For example, he could have been experimented on by Orochimaru and gained some strange powers as a result. And he returns to the village later to protect Naruto from the threats that are coming towards him.
One common theme is power. Often, the fanfictions explore how Naruto's connection with the fox gives him new and enhanced powers. He might use these powers to fight stronger enemies or to protect the village. For example, in many stories, Naruto can access different forms related to the fox that boost his strength and speed.
In some stories, the fox eyes might give Naruto a kind of hypnotic or intimidating power. Enemies might be momentarily stunned or less able to fight effectively when they look into his fox eyes. This could be a unique advantage in battles, allowing Naruto to gain the upper hand without having to use as much physical force.
It could make Naruto more responsible. Since he has to take care of the baby fox, he'll have to think about another being's needs. For example, he can't just go on long missions without making arrangements for the fox.
Well, one possible plot could be that the baby fox has some special powers. Maybe it can communicate with Naruto telepathically and helps him in his ninja missions. For example, it could sense danger before Naruto does and warn him.
Some fanfictions might introduce new characters related to the fox kit. Maybe there are other creatures or people who have a connection to the fox kit's origin. These new characters could bring in new conflicts or alliances, adding more depth to the story and interacting with Naruto and his friends in various ways.
One popular 'naruto has a fox' fanfiction is 'The Fox's Bond'. In this story, Naruto's connection with the fox is explored in a unique way, delving into how they communicate and work together. It has an interesting plot that keeps readers engaged.