It's possible that the main characters could also include some of the antagonists from the original series. Maybe they are behind the cause of the fire and ash, or they take advantage of the chaos to further their own goals. Naruto and his allies would then have to face these enemies while also dealing with the desolate environment.
Obviously, Naruto is likely to be one of the main characters since it's in the title. There might also be characters like Sasuke, who could be Naruto's rival or ally in the context of this fanfiction related to the god of fire. Sakura could also be there, perhaps as a healer or someone who helps Naruto understand his new powers.
Naruto is surely the central character in this fanfiction. Besides, characters like Kakashi could be involved. He might be Naruto's mentor in controlling and understanding his new 'king of fire' powers. And villains from the Naruto universe might also appear. They could be envious of Naruto's power and try to take it away or use it for their own evil purposes. So, a variety of characters from Naruto's world could be main characters in this fanfiction depending on the plot.
Since there are many 'guardian of fire' Naruto fanfictions, the main characters can vary greatly. It could still have Naruto as a main character, along with the new 'guardian of fire' character, who could be an original creation for the fanfiction.
It could be the descendants of the original Naruto characters. For example, Naruto's son might be one of the main characters, carrying on his father's legacy and the will of fire.
Another character that could be prominent in 'Naruto Green Fire Fanfiction' is Kakashi. He could play the role of a mentor, guiding Naruto and the others in understanding the new and potentially dangerous green fire. His experience and wisdom would be valuable in dealing with this new element in the ninja world.
Obviously, Naruto and the Fire Daimyo are the main characters. Naruto is the well - known ninja from Konoha, and the Fire Daimyo is the leader of the Fire Country.
Naruto would be a likely main character. Since he is the hero of the Naruto series, he could be involved in any story related to the Fire Daimyo. His friends like Sasuke or Sakura could also be part of it. They might be sent on a mission by the Hidden Leaf to protect or assist the Fire Daimyo.
Often, Naruto himself can be a main character. He might be exploring the new power of dark fire, either trying to master it for the good of the village or facing the internal struggle of whether to use such a dangerous power. Sasuke could also be a main character. Given his own complex relationship with power and his past, he could be drawn to the allure of dark fire and how it could help him achieve his goals.
Sasuke is also commonly involved. His rivalry with Naruto can be further explored when blue fire is added to the mix. He might try to master the blue fire himself or be in conflict with Naruto over the power it represents.
Naruto himself could be a main character. He has a natural inclination towards befriending powerful beings, and his determination would make him a great fit to interact with the fire and ice dragons. Sasuke could also be a main character, with his Sharingan potentially having some unique interactions with the dragons' powers.