It depends on the specific fanfiction, but it could still feature Naruto, Sasuke, and Sakura as main characters. They might have new roles or developments related to the dark and light chakra concept.
One interesting concept could be how the dark chakra affects a character's personality. For example, it might make them more aggressive or unpredictable. Another could be its origin, like if it's from an ancient curse or some dark experiment.
One possible storyline could be that Naruto struggles to control this dark chakra. He might accidentally harm his friends and then have to go on a journey to find a way to suppress or purify it. For example, he could seek out ancient jutsu or visit reclusive sages.
Well, one interesting concept could be the exploration of how dark and light chakra interact in unique ways not shown in the original Naruto series. Maybe there are new jutsu or abilities that are created from the combination or conflict of these two types of chakra.
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.
It could be a rogue ninja who is also after the power of the chakra chains. This ninja might see Naruto as a threat and try to eliminate him to get the chains for himself.
One interesting 'dark chakra Naruto' fanfiction could be one where Naruto discovers a hidden dark chakra within himself during a difficult mission. This dark chakra gives him new and unexpected powers, but also comes with a struggle to control it as it has a mind of its own.
In fanfiction, the dark chakra can make Naruto more brooding. Instead of his usual optimistic self, he becomes more withdrawn as he struggles with the new power. For example, he may question his own identity and whether he can still be the hero everyone expects him to be.
One idea could be Naruto using the chakra chains in a unique way to fight a powerful new enemy. For example, he might combine them with his shadow clones to create a multi - pronged attack. Another could be the origin of these dark chakra chains, perhaps they are linked to an ancient and evil power within Naruto that he has to learn to control.
One interesting concept could be a character unlocking the hidden potential of the chakra gates in a unique way. For example, they might discover a new sequence of opening the gates that gives them powers beyond what was thought possible in the original Naruto lore.