There's no way to know for sure who the main characters are without reading the 'naruto noble six fanfiction'. However, they might be six characters who have some connection to the noble aspects in the Naruto world. For instance, they could be descendants of important ninja families or they could be ninja who uphold noble values. They may have their own personal arcs and backstories that the fanfiction explores, such as one character might be trying to redeem their family's name while another is on a quest for power to protect the weak. But until we read it, it remains a mystery.
Obviously, Noble Six is one of the main characters. In the RWBY - Noble Six fanfiction context, they are usually the outsider from a different world or setting. Then there are the characters from RWBY like Ruby, Weiss, Blake, and Yang. Ruby, with her leadership and powerful scythe skills, often has interactions with Noble Six.
Master Chief is a common character paired with Noble Six. Given their both being iconic Halo characters, fans like to imagine how their different combat styles and personalities would interact. Master Chief's stoic and experienced nature could contrast or complement Noble Six's own skills and traits.
The main characters would be Noble Six and Kait. Noble Six is from a different part of the Gears universe, and Kait is a key character in Gears of War 4.
Since it's a fanfiction, it's all up to the creativity of the author. 'Naruto noble six fanfiction' might center around six individuals who are distinct in the Naruto setting. They could be a secret group that has been overlooked in the original Naruto story. The story might detail their origin, their training, and how they become a force to be reckoned with. It could also involve their relationships with other ninja clans and how they influence the overall power balance in the Naruto world. For example, they could be a group of ninja with special abilities that are different from the known jutsu in the Naruto series, and the fanfiction could explore how these abilities are used in different situations.
In a fanfiction, Noble Six could be a mysterious figure in the Naruto universe. Yugito might be the one to first encounter Noble Six and be intrigued by their different fighting style. Naruto, being the main hero, would then get involved. They could go on a journey to discover the origin of Noble Six and in the process, face many challenges. This could involve battles against rogue ninja or even other tailed beasts. Their combined strength and friendship could be the key to saving the day.
In this fanfiction, Naruto is bound to be a main character. Alongside him, there could be antagonists who are interested in the power of the Six Paths Senjutsu for their own evil purposes. These could be new villains or old foes with a new motivation. Also, characters like Jiraiya might make an appearance, either through flashbacks or some sort of spiritual guidance, as he was Naruto's mentor and had knowledge about various ninja arts, which could be related to the Six Paths Senjutsu in some way.
Obviously, Naruto is one of the main characters as the story is centered around him being the son of six paths. Sasuke could also be a main character as he has always been Naruto's rival and friend. Their relationship would likely be further explored in this fanfiction.
The main characters are Noble Six and Carolina. Noble Six brings a sense of mystery and raw combat power to the story. Carolina, on the other hand, has her own backstory, her own goals and her own way of dealing with the chaos of the Red vs Blue world. Their relationship, whether it's a partnership, a friendship or something more, is what would drive the fanfiction forward.
One common theme could be Naruto's self - discovery in relation to the noble six. Maybe he realizes how he embodies these qualities over time.
Sasuke is often involved too. In many fanfictions, his rivalry with Naruto takes on a new dimension when the Six Paths power comes into play. He might either be jealous of Naruto's new power or try to find a way to equal it on his own.