In the fanfiction, it could be due to a powerful enemy's attack that has affected his breathing ability. For example, if the enemy has used a special jutsu that restricts air intake or affects the lungs. It might also be related to some kind of poison or gas in the environment that he has been exposed to, which is a common plot device in many fictional stories.
Perhaps it has something to do with his own internal chakra imbalance. If his chakra is disrupted in a certain way, it could potentially lead to problems with his physical functions, such as breathing. Another possibility is that he is in a high - stress situation, like a life - or - death battle, where his body is so tense that it affects his normal breathing pattern.
Maybe he's in a tight situation like being trapped in a small space or under some kind of magic spell.
Maybe he had a bad experience as a kid. Like he almost drowned once, and that made him too scared to learn how to swim properly.
In some fanfictions, the author might make fem Naruto not talk to create an air of mystery around her character. By not speaking, she becomes more of an enigma, which can draw readers in. It could also be related to her character development. For example, she may be shy or introverted at the start of the story and gradually learn to open up and speak as she grows and overcomes her insecurities.
One possible reason could be the stress of his ninja duties. He has so many missions and responsibilities that his mind is constantly racing, making it hard to relax and fall asleep.
: Sasuke could be a possible cause, not out of malice but maybe during an intense fight where things get out of control. They have had some really rough battles, and in the heat of the moment, Sasuke could accidentally use a technique that affects Naruto's ability to breathe. Also, there could be some new villain in the fanfiction that we don't know about yet, who has a specific grudge against Naruto and targets his breathing as a way to weaken him.
One possible reason could be that he was severely injured in a battle. Maybe he got his legs broken or had some internal damage that affected his ability to move them. For example, if he fought against a really powerful enemy who used a jutsu specifically targeting his legs, it could leave him unable to walk.
Perhaps as a sign of rebellion. If Naruto has some issues with the established norms in his village or with the ninja system in general in the fanfiction, getting piercings could be his way of defying authority and showing that he won't be restricted by the traditional ways.
One possible reason could be the trauma he has faced in his life. For example, the loss of his parents at a young age and the constant feeling of being an outcast in the village. These past experiences might resurface in his dreams as nightmares. Another reason could be the pressure he feels as he grows older, like the weight of his responsibilities as a ninja and his role in protecting the village. Also, the fear of losing his friends, who have become like family to him, might haunt him in his sleep.
One possible reason could be that Naruto has a different love interest in his heart, like Hinata. In the original story, his relationship with Sakura was more of a friendship - like bond. Another reason might be for the sake of creating an unexpected plot twist in the fanfiction. Maybe the writer wants to explore different emotional and relationship dynamics that don't follow the typical Naruto - Sakura pairing.
There could also be political reasons. Some factions within Konoha might have seen Naruto as a tool or a threat to their own political power. His influence and popularity could have disrupted the existing power balance, leading to animosity from those who wanted to maintain the status quo.
One reason could be that Naruto might be too focused on his ninja goals. He has always been determined to become Hokage and might see a relationship as a distraction. In fanfiction, his single - minded pursuit of his dream could lead him to reject Hinata.