Naruto might also call upon the help of his friends. For example, he could signal to Sakura, who could use her medical ninjutsu skills to create a protective field around AM. Meanwhile, Naruto distracts Sasuke with his own attack, like a barrage of shuriken, so that Sasuke's fireball misses AM.
One way could be that Naruto uses his wind - style jutsu. He manipulates the wind to create a gust strong enough to blow Sasuke's fireball off course, away from AM. This would be a display of Naruto's control over different elements.
Well, it depends on the specific setting of the fanfiction. If it's set in a modern - day AU (alternate universe) where Naruto and Sasuke still have their powers, Naruto could be using his enhanced speed to reach Amy in time. He might also have some sort of new power or ability that we haven't seen in the original series that helps him save Amy more effectively. For example, he could have a power that allows him to absorb or deflect the fireball instead of just dodging it.
Well, in the fanfiction, Naruto might use his own jutsu, like the Rasengan. He could quickly form it and counter Sasuke's fireball, thus saving Ami. Maybe Naruto's quick reflexes and his determination to protect Ami play a big role here.
One consequence could be that it deepens the rift between Sasuke and Naruto. Sasuke might see Naruto's act as interfering in his business or as a sign that Naruto is choosing Ino over him in some way.
In this kind of fanfiction, Naruto might use his own jutsu like the Rasengan. He could quickly form the Rasengan and counter Sasuke's fireball, dissipating it before it reaches AM. This would require Naruto's quick reflexes and mastery over his chakra control.
One consequence could be a change in the relationship between Naruto and Sasuke. Sasuke might become more enraged or, on the other hand, he could start to question his actions. As for Naruto and Ami, their bond might grow stronger. Ami would likely be very grateful to Naruto, and this could lead to a closer friendship or even something more in the future of the fanfiction.
Maybe Sasuke is being manipulated by an evil force that wants to get at Naruto through Hinata. Since Hinata is important to Naruto, targeting her would be a way to hurt Naruto.
Perhaps Naruto has some sort of premonition about Sasuke's danger. He follows his gut feeling and finds Sasuke trapped by Haku. He then uses his Uzumaki bloodline power, something that might be enhanced in fanfiction, to disrupt Haku's chakra flow and save Sasuke.
Well, Naruto could use his Shadow Clone Jutsu. He might create a bunch of clones to form a shield between Ino and Sasuke's fireball. The clones could absorb the impact and heat of the fireball, protecting Ino from harm.
One consequence could be that Sasuke becomes even more enraged at Naruto. Since Sasuke's pride might be hurt by Naruto interfering, he could vow to get revenge on Naruto later. Another consequence is that Amy might become indebted to Naruto. She could then offer to help Naruto in his future battles or quests in the fanfiction.
Simple. Naruto is a hero at heart. He can't stand seeing anyone being hurt, especially his friends. Ino is his friend, so he has to save her from Sasuke.