Sasuke is another character who might be involved as a main character in such fanfictions. If the red - eyes concept is related to the Sharingan or some new form of eye power, Sasuke's connection to the Uchiha and their eye powers makes him a likely candidate to be part of the story. The red - eyed character might be his ally or rival.
Kakashi could also be a main character in 'Naruto Red Eyes Fanfiction'. He has his own experiences with eye powers (the Sharingan). So, in a fanfiction where there are red eyes with new powers, Kakashi could play a role in mentoring or being suspicious of the red - eyed character, adding an interesting dynamic to the story.
Sasuke is also frequently a main character in these fanfics. Imagine if Sasuke had red eyes instead of his Sharingan. It could completely change his character arc. He might be even more of an outcast or have a different set of powers that make him both feared and respected. And then there are the Akatsuki members. Some fanfics might make one of them have red eyes and explore how that changes their role within the organization and in the overall Naruto story.
Obviously, Naruto is a main character in these fanfictions. He's usually the one who gets the red eyes and the connection to the Darkness Dragon. Sasuke might also be involved, either as a rival who is intrigued by Naruto's new power or as a partner in exploring the secrets of the red eyes. Sakura could be there as well, perhaps trying to help Naruto control the power so it doesn't consume him. And sometimes, characters from other clans or villages might make an appearance, like Gaara, who might be interested in the power because of its potential threat or its possible use in protecting his own village.
Often, Naruto himself can be a main character in Naruto cold eyes fanfiction. The story could explore how he interacts with a character who has cold eyes. Another common main character could be a new, original character created specifically for the fanfiction, who has these cold eyes and has a significant role to play in the Naruto - inspired world.
Often, Naruto himself might be associated with it. Since he is the main character in the original series, fanfiction writers may give him sage eyes and explore how it changes his character and abilities.
Sasuke is a very popular character in such fanfictions. Since he already has the Sharingan in the original Naruto series, fanfic writers often expand on his abilities with the Sharingan or give him new eye - related powers. They might explore how he further masters his Sharingan or what would happen if he obtained another type of eye power.
Ruby Rose is often a main character as she has silver eyes in the RWBY series. Fanfictions might focus on her growth and development, especially in relation to her silver - eyed powers.
Naruto is likely to be one of the main characters since it's a Naruto - related fanfiction. His character might be central to the story, either in relation to the 'Eyes of Basilisk' or in trying to counter their power.
In 'naruto new eyes fanfiction', Naruto is the central figure. But characters like Kakashi could play a significant role. He has a lot of knowledge about different types of eyes and their powers, so he could be mentoring Naruto on how to use his new eyes effectively. Also, characters from other villages might be introduced as they are interested in Naruto's new power and either want to steal it or form an alliance with him.
It's hard to say for sure without reading the specific fanfiction, but it could feature Naruto himself as one of the main characters. Maybe he somehow acquires the 'Eyes of God' and has to deal with the newfound power.
The main characters can include the gunsmith, who might be an outsider to the traditional ninja world but has a unique skill set. Another could be a ninja who becomes the gunsmith's protector or partner. For example, Sasuke could be interested in these new firearms as a way to enhance his own power. And sometimes, there are original characters created specifically for the fanfiction, like a rival gunsmith who tries to outdo the main gunsmith in creating the most powerful weapons.