Another possibility is that Naruto, being the protagonist and having a great willpower, manages to find a way to break the natural laws of death in the Naruto world. This could be through his understanding of the cycle of life and death, which he has witnessed multiple times. He might have some sort of epiphany that allows him to use his own life force or chakra in a self - sacrificing way to revive everyone.
He could use his strong bond with the Nine - Tails. The Nine - Tails has a vast amount of chakra and unique abilities. Naruto, having a symbiotic relationship with it, might find a way to use the Nine - Tails' chakra in a way that can bring back the dead. For example, he could use it to reverse the effects of certain death - causing jutsus or even create a large - scale resurrection jutsu.
Well, in some fanfictions, Naruto might use some super powerful jutsu that he either discovers or creates. Maybe it's a new form of the Rasengan combined with some sealing techniques. It could also be that he taps into some ancient power or makes a deal with some sort of god - like entity within the Naruto universe.
One consequence could be an imbalance in the world's population. There might be too many people for the existing resources, leading to shortages of food, water, and living space.
Hashirama's revival might also bring back old wisdom and knowledge. He could teach the new generation of shinobi things that have been lost over time. However, there could also be political issues. Some might not be happy with a long - dead Hokage coming back and potentially interfering in current affairs. And his revival could also have an impact on Naruto's own growth. With Hashirama around, Naruto might have to re - evaluate his role as a leader and a shinobi.
It could be that his new 'godlike' power has isolated him. People might be either in awe or afraid of him, and he may feel that he can't be close to others as before. So he acts coldly as a defense mechanism.
One way could be through some powerful forbidden jutsu. Maybe he discovers a long - lost scroll that contains a jutsu specifically designed to bring back the dead. However, such a jutsu would likely come with a great cost, like sacrificing a large amount of his own chakra or even his life - force.
On a personal level, Naruto would finally get the family he always wanted. But it might also bring some confusion and adjustment issues. His parents would be from a different time, and they'd need to adapt to the new world Naruto lives in. For example, they might be shocked by the new technology and the changes in ninja warfare.
Maybe he got some kind of curse. In the Naruto universe, there are all sorts of dark magic and curses. If he was cursed, it could make him withdrawn and cause him to ignore everyone.
It could also be that Naruto has had some sort of revelation about himself or the ninja world. He might have realized that the relationships he has been in were holding him back in some way. Maybe he wants to focus on self - improvement and growth, and he believes that being alone is the best way to do that. He could be trying to find his true self without the influence of others.
One possible reason could be that Naruto has seen or experienced something that makes him distrust or fear those around him. Maybe he has discovered a dark secret about the village or his friends that has shaken his beliefs.
One possible reason could be a powerful genjutsu cast over the village. Maybe an enemy ninja with strong illusionary powers managed to make everyone forget Naruto. It could also be due to some sort of curse. For example, a dark curse was placed on Naruto that made people's memories of him fade away gradually.
Maybe in that fanfiction, Naruto's over - eagerness to be recognized could be misconstrued. His loud and boisterous nature might annoy people. For example, if he constantly interrupted others or pushed his ideas too hard without considering others' feelings, it could lead to dislike.