Sasuke could be a great candidate. He has always been a bit of an enigma, with his brooding nature. He could be hiding a new power or a different side of his personality behind a mask, either self - imposed or as a result of some outside influence. Maybe he's trying to hide his true intentions from Naruto and the others as he pursues his own goals.
It could be a new, original character. For instance, a young ninja from a small, forgotten clan. This character might be hiding their clan heritage behind a mask because their clan has been shunned or feared in the past. Throughout the fanfiction, they interact with the main Naruto characters and their story unfolds as they struggle with whether to reveal their true identity or keep it hidden.
It could be Sasuke. He might be wearing a mask for some mysterious reason, like hiding his new powers or a new allegiance. Maybe he's on a secret mission that even Naruto doesn't know about at first.
It might also be a completely new character created for the fanfiction. This new character could be wearing a mask for a unique reason, like hiding a special power or being part of a secret organization. The fanfiction could then revolve around this new character's journey and how the mask plays a role in it.
It might also be a new character created specifically for the fanfiction. This character could be someone who has infiltrated the Hidden Leaf Village, living behind a mask of false loyalty while having their own secret motives and goals.
One possibility is that the story could focus on a character who has been living a double life. They are hiding their true self behind a mask, perhaps for protection or because they have a secret mission. In the Naruto universe, it could be a ninja who is secretly working against a powerful enemy within their own village. They use the mask to conceal their identity and actions from those around them.
Astrid is also a possibility. She's a strong - willed character, but perhaps there's more to her than what we usually see. She could be hiding her softer emotions or insecurities behind a tough - girl mask. For example, she might be secretly worried about her relationship with Hiccup or her place in the tribe.
An orphan with no known family could be the main character. They discover they have a hidden bloodline through a series of events. It could be a bloodline that gives them the ability to see the past or future in dreams. This character would then be on a journey to figure out where they came from and what their power means, all while trying to fit into the ninja society.
Samui could be a great main character. She is a strong and intelligent kunoichi from the Hidden Cloud. Her skills in combat and her calm demeanor would make for an interesting story as she takes on various challenges within the village and outside.
It could be an original character created by the fanfiction writer. This character could be from a minor clan in the Naruto universe but has extraordinary intelligence and potential.
Kakashi could be another option. He is a highly experienced and intelligent ninja. If he came across the skull mask, he would approach it with caution. He might study it first to understand its origin and power before deciding whether or not to use it. His calm and collected nature would be a great contrast to the potentially wild power of the mask.
It could be a new villain. A character with a cracked mask might be introduced as a powerful adversary. The cracks in the mask could be a sign of their unstable power or a damaged psyche. They could have a vendetta against Naruto and his friends, and the story would be about Naruto trying to stop their evil plans.