One possibility could be that in his second life, Naruto has all the knowledge from his first life. So he can avoid making the mistakes he made before and become an even stronger ninja much faster. He might also use his past experiences to better understand his friends and enemies, and form different relationships.
In the 'naruto lives two lifes fanfic', it could be that Naruto's second life starts at a different point in time. For example, if his second life starts during the Fourth Great Ninja War, he could use his knowledge of the future to change the outcome of the war. He might be able to save more lives and prevent some of the tragedies that occurred in the first war. He could also influence the development of other characters in ways he couldn't in his first life, such as helping Sasuke make different choices earlier on.
Another possibility is that Orochimaru could be the main antagonist in a different way in Naruto's second life. Orochimaru was always interested in power and immortality. In Naruto's second life, Orochimaru might see an opportunity to use Naruto's unique situation to further his own goals, whether it's by trying to possess Naruto or by using his knowledge of the future to gain more power in the ninja world.
One possible plot could be that Naruto and Goku end up in a strange new dimension where they have to live together. They start by trying to understand each other's powers. Naruto is amazed by Goku's Saiyan abilities like the Kamehameha wave, while Goku is intrigued by Naruto's ninjutsu. They then team up to face common enemies in this new world. Maybe there are villains from both their universes that have also been brought there. Together, they train and learn from each other, with Naruto teaching Goku about stealth and strategy, and Goku showing Naruto how to push his physical limits even further.
Well, it could be that Naruto is exiled for some reason and has to live in a cave. In the cave, he discovers some ancient secrets or artifacts. These could be related to the origin of chakra or some long - lost ninja techniques. He then uses this knowledge to his advantage and maybe even changes the ninja world for the better.
The plot could involve them facing a common enemy. Since they both come from different but powerful universes, their combined strength would be interesting to explore. They could start as strangers in the fanfic, gradually become friends while living together, and then team up to fight this new threat.
In this fanfic, Naruto could be on a secret mission in the red light district. He has to blend in and gather information. Along the way, he meets a diverse group of characters, some of whom are being forced into the unsavory lifestyle. Naruto decides to not only complete his mission but also to rescue those in need. He uses his charisma and strength to stand up against the powerful forces that control the district, ultimately bringing a glimmer of hope to the dark place.
In this fanfiction, perhaps Hinata and Naruto are living together and learning more about each other on a deeper level. Hinata could be teaching Naruto some of the traditional Hyuga clan techniques, while Naruto shows Hinata some of his unique jutsu. Their living situation might also involve a lot of visits from their friends like Sakura and Sasuke, creating some really fun and heart - warming group dynamics.
Maybe they start a family and Naruto becomes a great Hokage while Sakura takes care of their home. They face daily challenges together like any normal couple.
Well, one possibility is that Naruto forms a unique bond with the foxes. Maybe he learns their ways of survival, like how to hunt in the forest or find hidden water sources. The foxes could also teach him some secret ninja skills that are exclusive to their kind.
Well, one possible plot could be that they decide to live together to train more intensively. They might share their different jutsu knowledge, like Naruto teaching Sasuke about Sage Mode and Sasuke teaching Naruto some of his unique Uchiha techniques. This would lead to them becoming even stronger together.
Perhaps in this fanfiction, Naruto lives in the sewers because he is hiding from some sort of threat in the village above. He might be wrongly accused of a crime he didn't commit. While in the sewers, he meets other outcasts or misfits who have also sought refuge there. Together, they form a sort of underground community. Naruto then tries to clear his name from the sewers, using the resources and the new friends he has made to gather evidence and prove his innocence.