In Naruto dark chakra fanfiction, Sasuke is frequently a central figure. Given his complex character arc and his inclination towards power - seeking, it's easy to envision him being affected by or exploring dark chakra. Naruto too can be a main character. His strong will and connection to positive chakra could be put to the test when faced with the allure of dark chakra. Another character often involved is Kabuto. He has a history of being involved in dark and underhanded schemes, so it's not a stretch to see him in stories centered around dark chakra. There are also some original characters created by fanfiction authors that are specifically designed to interact with the concept of dark chakra in unique ways.
In many naruto golden chakra fanfiction, Naruto is at the center. Kakashi could be an important character as he is Naruto's mentor. He might guide Naruto in controlling and using the Golden Chakra. Hinata could also be a main character, as she has deep feelings for Naruto. Her love for Naruto could be a driving force in some stories, either giving Naruto emotional support as he deals with the power of the Golden Chakra or even having her own role in helping him unlock more of its potential.
Sasuke could be another key character. There could be a plot where Sasuke is initially skeptical about Naruto's new chakra sage abilities but then comes to see their value in protecting the shinobi world. And Jiraiya, as Naruto's former mentor, might appear in flashbacks or even in some spiritual form to give Naruto advice on his chakra sage journey.
Naruto himself is often involved. Since he is the main character of the original series, it's natural for him to be part of fanfictions related to the chakra fruit. He might be the one to discover it or have to protect it from villains.
Sakura is often involved. Since she's a medical ninja, it's natural for her to be associated with the chakra scalpel in fanfiction. She might be seen using it in new and innovative ways to save lives or in battles against strong opponents. Another common character is Naruto himself. Even though he's not primarily a medical ninja, in some fanfics, he could learn to use the chakra scalpel in his own unique way, perhaps combining it with his massive chakra reserves and shadow clone jutsu.
Obviously Naruto is the main character as the golden chakra cloak is related to him. Sasuke might also be involved as his rival. Kakashi could play a role as Naruto's mentor, guiding him in controlling this new power.
The Nine - Tails also plays a major role. In a dark Naruto story, the Nine - Tails could be more of a corrupting influence, whispering dark thoughts into Naruto's mind and fueling his descent into a more menacing figure in the ninja world.
Naruto himself could be a main character. He might be tempted to use dark summons to gain power to protect his village or friends. For instance, in some fanfictions, he discovers a dark summon that could potentially defeat a powerful enemy threatening Konoha, but at a great cost.
Naruto himself is often a main character. He's usually the one who stands up against the dark guild's evil plans. Sasuke might also be involved, as his power and sometimes ambiguous moral standing can add interesting dynamics when dealing with the dark guild.
Obviously Naruto himself is a main character as he is the one under the dark control. Then there would be his friends like Sasuke and Sakura. Sasuke might be crucial in trying to understand and counter the dark power since he has his own powerful abilities.
Naruto himself is often involved. He might be either tempted by Dark Hadou or have to fight against those who use it. Sasuke could also be a main character in such fanfictions. His quest for power could lead him to explore the Dark Hadou. And then there's Kakashi, who with his experience and knowledge, might be involved in trying to stop the spread of Dark Hadou.