In certain fanfictions, the Shinigami Mask gives Naruto access to a special form of jutsu. It could be a jutsu that combines the power of the Shinigami with his own Uzumaki bloodline. This new jutsu might be extremely powerful, allowing Naruto to break through defenses that were previously unbreakable. It could also have some side effects that Naruto has to learn to control, like a drain on his energy or a temporary loss of his normal abilities.
The Shinigami Mask could enhance Naruto's chakra control. Since the mask is often associated with powerful and otherworldly forces, it could help Naruto manipulate his chakra in ways he couldn't before. For example, he might be able to use his chakra to create illusions that are so real, they can physically harm his enemies. This is all part of how the mask can transform his abilities in fanfiction.
His speed and strength could increase. Shinigami powers might give him a boost in physical abilities as they are often associated with otherworldly strength.
It might give Naruto new types of jutsus. For example, if the Kitsune have the ability to create illusions, the mask could grant Naruto the power to use more advanced genjutsu. He could use these illusions not only in battle but also to deceive his enemies in strategic ways outside of combat.
There might be a fanfiction where the Shinigami Mask is actually a key to an alternate dimension full of powerful and strange creatures. Naruto, being the curious and brave character he is, ventures into this dimension with the mask and has to face numerous challenges and make new allies to find his way back home.
His combat abilities would likely be boosted. With the hollow mask, Naruto could have increased physical capabilities, such as stronger punches and kicks. His reflexes might also be enhanced, allowing him to dodge attacks more easily. He could potentially use the mask's power to disrupt his opponents' chakra or energy, similar to how hollows can disrupt spiritual energy in Bleach.
If the gift is a power - enhancing jutsu, Naruto could become much stronger physically and in terms of his ninja abilities. This would make him more confident in battles and able to take on tougher opponents.
In such fanfiction, Naruto's personality could be a mix of his old self and a new, more complex version. He would still be the determined and kind - hearted Naruto at heart. However, the power of the hollow mask might make him more secretive. He might keep things from his friends and mentors for fear of them trying to take the mask away. This internal conflict between his old and new self could be a major part of his character development.
Naruto's personality could shift towards being more reserved. As a Shinigami, he has to deal with the weight of handling souls and the concept of death. This could make him think twice before acting impulsively like he used to. He may also develop a more empathetic side towards those who are about to die or have lost loved ones, as he now has a closer connection to the afterlife.
When Naruto is trained by the Shinigami in a fanfic, his ninja skills are bound to change significantly. His Rasengan, which was already a powerful attack, could be upgraded to something more formidable. It could now have the ability to target the soul of the opponent directly. His stealth skills might also improve as he learns to move more like the Shinigami, which is a being that can appear and disappear mysteriously. Additionally, his ability to communicate with other beings, like summons, could be enhanced as he gains a better understanding of the spiritual realm through the Shinigami's training.
In the fanfiction, Naruto's emotionless mask might make Sasuke feel like he's lost his rival. Naruto's lack of emotional response could cause Sasuke to question if Naruto still cares about their bond. Sasuke might start to distance himself, thinking that Naruto has changed too much. However, as the story progresses, Sasuke could realize that the mask is just a facade and they could start to repair their relationship.
Well, obviously, the addition of the face mask gives him a more mysterious look. His usually open and friendly face is partly hidden, which might make others view him with more caution or curiosity.