Well, he might have the black cloak fastened at his neck, and it would flow down to his ankles. His headband would still be visible, but the cloak would give him a more menacing or at least a more solemn look. The cloak could be made of a rough, durable material, like something a ninja on a long - term mission would wear. His blue eyes would seem even more piercing against the backdrop of the black cloak.
In fanfiction, Naruto wearing a black cloak could symbolize a new phase in his life. Maybe he's become more of an anti - hero or is on a secret mission. It could also be a sign of him joining a new group that has a darker aesthetic.
It could be a new character created specifically for the fanfiction. Maybe a wandering ninja who uses the black cloak to hide their identity and past traumas.
One interesting Naruto fanfiction related to the black cloak could be about a mysterious character who wears a black cloak and has a hidden agenda within the Naruto universe. Maybe they are secretly working against the Akatsuki or have a connection to an ancient jutsu that only they can unlock while wearing the cloak.
A fanfiction could revolve around Naruto being given an Akatsuki cloak as a gift from an unexpected source. Maybe a former Akatsuki member who has turned good. Naruto then has to decide what to do with it. He could modify it to represent his own ideals and use it as a symbol of unity between the Akatsuki remnants and the Hidden Leaf, working towards a more peaceful ninja world.
It depends on your perspective. Some might consider it realistic fiction as it could potentially draw inspiration from real-life elements or situations, but others might not see it that way.
One idea could be that Naruto wears a kimono for a special diplomatic event in the Hidden Leaf. It could be a traditional kimono passed down in his family, and while wearing it, he has to learn the proper etiquette associated with it, which leads to some humorous situations as he's not used to such formality.
The plot could be Naruto getting cursed by a jutsu that makes him have to wear the Akatsuki cloak to survive. As he wears it, he slowly starts to understand the Akatsuki's ideology from a different perspective. He then tries to change the Akatsuki from within, using his own values to influence the members.
The cloak could make Naruto more confident. If it has special powers, he would feel more capable and in control. For example, if it gives him the power of invisibility, he might start to take more risks in battles and become bolder in his strategies.
How about a talking cat? The cat could have been a victim of the black cloak's magic but managed to retain some of its form. It could act as a guide for Serafina, using its knowledge of the manor's hidden passages and secrets that it learned before being attacked by the cloak.