Kisame Hoshigaki is often associated with it. Given his shark - like appearance and his use of the Samehada, which is a large and unique sword, he could be easily incorporated into fanfiction involving the 8 Sword Style. His brute strength and combat skills would make for an interesting take on how he might adapt to or already be related to the 8 Sword Style.
Some original characters created by fanfiction authors can also be popular in this regard. These are often self - inserted or entirely new characters designed specifically to showcase the 8 Sword Style. They might have unique backstories that explain their connection to the style, such as being descendants of an ancient sword - smithing clan that had a secret knowledge of the 8 Sword Style.
Naruto himself can be a central character in such fanfictions. Given his own vast chakra reserves and his ability to learn new techniques quickly, he could be the one to unlock the true potential of the chakra chains. He might use them in a battle against a powerful new enemy, perhaps one that is immune to his regular jutsu but vulnerable to the unique properties of the chakra chains.
Some fanfictions might link the swords to the Akatsuki members. They are powerful and their motives could be tied to the acquisition and use of these powerful elemental swords. For example, Pain might be interested in the swords to further his goal of bringing pain and chaos. His Rinnegan could potentially have some unique interactions with the powers of the swords.
There could also be a mysterious and powerful swordsman character who is a master of the 9 sword style. They play a crucial role in the fanfiction, perhaps as a mentor to the other characters or as a key figure in a major conflict that involves the 9 sword style.
Sasuke is often involved. His natural affinity for sword - play and his powerful abilities like the Sharingan make him a prime candidate for fusion - related stories. Fans like to imagine him fusing his sword skills with other strong characters.
Sasuke is often a character associated with black chakra in fanfiction. Given his natural inclination towards power and his dark past, it's easy to imagine him being connected to such a powerful and mysterious form of chakra.
Often, Naruto himself might be associated with it in some fanfictions. Given his status as the protagonist, it's not uncommon to give him such a powerful ability. Another could be Sasuke, as his power - hungry nature in the original series could be explored further with the God Release.
Another character could be Kakashi. As a skilled and experienced ninja, he could play a role in guiding the character who obtains the Shinju fruit. He might be the one to recognize the true potential and danger of the fruit and try to ensure it is used for the greater good of the ninja world.
Sometimes, characters from other villages might also be involved. Maybe a ninja from Konoha who has a special encounter with the Nidaime Otokage. This could lead to an interesting exchange of ideas or a conflict that drives the story forward.
One of the main characters could be Hinata. Since she has the Byakugan, a fanfiction might explore the idea of her evolving it into a godlike doujutsu. Another character could be Madara Uchiha. His return in some form and obtaining a godlike doujutsu would be an interesting plot point. And of course, there could be mysterious, unnamed characters that are the center of the story in the fanfiction, with their godlike doujutsu being the main focus.
Often, Naruto himself is associated with neon powers in fanfiction. Since he's the main character of the original series, it's common to see him gain these new powers. His friends like Sasuke might also be involved, either having their own neon - related abilities or being affected by Naruto's new powers.