One possible reason could be a major betrayal. Maybe someone he trusted deeply, like a close friend or a mentor, turned against him. This would make him lose faith in people and become cold as a form of self - protection.
His relationship with Sakura would definitely be affected. Sakura, who has always known the warm - hearted Naruto, would be shocked and confused. She might try to reach out to him at first, but if he keeps pushing her away, she could become frustrated or even give up. Their friendship would be strained.
Well, it's hard to say it's a widely popular genre on its own. The Naruto fandom has a vast range of fanfic types. While the idea of Naruto being a cold and distant shinobi might attract some readers who like exploring different character portrayals, it's not as mainstream as some other common themes like Naruto achieving new powerful jutsus or his relationships with other main characters. There are so many different takes on Naruto in fanfics, and this rather 'edgy' or different view might only appeal to a niche group within the large Naruto fan base.
One possible reason could be a major betrayal he experienced. Maybe someone he trusted deeply, like a close friend or a mentor, turned against him. This would make him more guarded and distant to avoid getting hurt again.
His friends would be confused and hurt at first. They are used to the warm and friendly Naruto, so this change would be a shock. Some might try to reach out to him, but if he keeps pushing them away, it could lead to a strain in their relationships.
One possible plot could be that Naruto experiences a great betrayal, perhaps by someone he deeply trusted in the village. This could make him lose faith in the bonds he once cherished and become cold towards others. He might start to isolate himself and focus only on his own power, believing that relying on others will only lead to more pain.
It might imply that in this fanfiction, Naruto is emotionally distant. For example, perhaps he has had some experiences that have made him withdrawn or less connected to the people around him. It could also mean that the events in the fanfiction are taking place at a distance from the main Naruto storyline, like in a different part of the Naruto universe that we haven't seen much in the original series.
Another reason could be the influence of a powerful and dark entity. If Naruto is somehow possessed or influenced by a dark chakra or a malevolent spirit, it might change his personality completely. He could start to push away people who care about him because the entity wants him to isolate himself and be more vulnerable to its control.
One reason could be to explore a different side of Naruto's character. In the original series, he's so warm - hearted, but by making him cold and distant, the writer can show how different events could have shaped him in an alternate way. Maybe he faced more hardships or betrayals that led to this change.