The purpose could be to protect the weak. Naruto has always been about protecting those who can't protect themselves. So his organization might focus on safeguarding small villages or groups that are vulnerable to attacks from rogue ninjas or larger, more aggressive villages.
One great Naruto purpose fanfiction is 'The New Path'. It focuses on Naruto exploring an alternative form of ninjutsu training. Another is 'Naruto's Hidden Purpose' which delves into his unspoken goals for the Hidden Leaf. And 'Purpose Beyond the Hokage' where Naruto tries to find a greater meaning for the shinobi world outside of being the Hokage.
First, decide on Naruto's new purpose. It could be something like saving a different village or mastering a new type of jutsu for a special reason. Then, create an outline of the main events that will lead to and from this purpose. For example, if his purpose is to save a village, think about what threats the village faces and how Naruto will overcome them.
Perhaps an old enemy from Naruto's past, who has somehow been resurrected with a new power and a new purpose. This enemy could be someone like Orochimaru, but with even more sinister motives and abilities. He might want to take over the world in a different way than before.
One idea could be Naruto exploring a new form of ninjutsu that he discovers in an ancient scroll. Maybe it's a long - lost technique that gives him the ability to control time on a small scale, like slowing down an enemy's attack.
Perhaps it's for exploration. Naruto is always curious about the world outside. The robots can be sent to explore dangerous or uncharted areas where it might be too risky for humans to go. They can collect information and report back to Naruto.
You can start by looking on fanfiction websites such as FanFiction.net or Archive of Our Own (AO3). Just type 'naruto purpose fanfic' in the search bar on these platforms, and they will show you a list of relevant stories.
One good 'naruto purpose fanfic' could be those that explore Naruto's journey to become Hokage in more depth. For example, a fanfic might focus on the challenges he faced during his training that were not fully shown in the original series. Another could be about his relationships with other characters like Sasuke, delving deeper into their bond and how it evolved over time.
In this fanfic, perhaps Naruto is trying to deceive everyone into thinking he's the dead last as part of a long - term strategy. He might be secretly training in a unique and powerful jutsu that he doesn't want anyone to know about until he's fully mastered it. So, by acting like the worst student, he has more freedom to experiment without interference.
At first, Naruto is likely to be confused and hurt. He has always considered the Leaf village his home and the villagers his family, so being banished would be a huge shock. He might feel betrayed.