Sometimes, the main character could be an established Naruto character like Naruto himself or Sasuke, but with a new twist where they somehow gain the ability to use light release. They would then have to learn how to control this new power and incorporate it into their existing fighting styles.
Sometimes, it's an existing Naruto character who is given the Light Release bloodline in an alternate universe story. For example, Naruto himself could be given this bloodline, which would change his fighting style completely. He could use his natural exuberance and combine it with the light powers to create some really unique and powerful jutsu.
Another possibility is that the main character is a sensei or an elder in the ninja village who has knowledge about the Chaos Release. They guide the younger generation in understanding this power. In some fanfictions, it could be a group of characters, each with their own relationship to the Chaos Release, working together or against each other depending on their goals.
Well, it could be an original character created specifically for the fanfiction. This character might be an outcast because of their Darkness Release abilities. Maybe they are trying to prove themselves in a world that fears their power.
There could also be a villain in the fanfiction who wields plasma release in a menacing way. This character might be from a secret organization, using the power to further their evil plans. Their plasma - based attacks would be a major threat to the heroes, forcing them to find ways to counter this dangerous ability.
There might be a mentor - like figure who has some knowledge about the dark release. This character could be important as they guide the younger or less experienced character with the dark release. Maybe they have a hidden past related to the power as well. In some fanfictions, this mentor could be an old ninja who has seen the power's potential and destruction in the past.
The main characters could be a new generation of ninja students in the Naruto world. They stumble upon the knowledge of 'Nightmare Release' and have to deal with the consequences. This could include a young ninja who has a natural affinity for this strange power and has to learn to control it while facing the challenges from other ninjas who fear or want to use this power for their own gain.
It's hard to say for sure as it's fanfiction. But it could be an original character created by the fan writer who has the Mirror Release ability. Maybe it's also Naruto himself who discovers this new type of release during his adventures.
It could be a new character who was born with the shadow release ability but was hidden away from the ninja world until now. They would be the center of the story as they learn about their powers and face the challenges that come with it.
One potential main character could be a new ninja who discovers they have the Ink Release. They are an outcast in their village at first because of this strange power but then learn to master it and become a hero. For example, a young orphan who is bullied for having this unusual ability.
Often, Naruto himself might be involved as he is the main character of the original series. He could be the one to discover or master a new particle release. Sasuke could also be a main character in such fanfiction, perhaps using his Sharingan in combination with particle release in unique ways.