Well, perhaps Naruto is sent to a dimension where Eevees are the main inhabitants. He has to adapt to living with them. He could form strong bonds with individual Eevees, like an Eevee that's really brave and they go on adventures together, exploring the new land and facing challenges that are unique to this world of Eevees.
Obviously Naruto is one of the main characters. And then, there would be the Eevees. There could be a special Eevee that stands out, like an Eevee that is more curious about Naruto than the others and becomes his closest companion among the Eevees.
I'm not sure specifically which 'A Sad Eevees Story' you mean. It could be about an Eevee in a Pokémon world that has lost its trainer, or maybe it was bullied by other Pokémon. Without more details, it's hard to say exactly.
It might be about Naruto living freely in a sense that he can make his own choices regarding his relationships. For example, he could choose his friends and allies more freely without political interference. In this fanfiction, he might not be bound by the traditional shinobi rules and hierarchies, allowing him to interact with different clans and villages on his own terms.
He could also interact with the scientists on Pandora. They might be interested in Naruto's abilities and study him. Naruto could in turn learn about their technology, which is so different from what he has in his own world. He might even help them solve some problems they have on Pandora using his ninja wisdom.
Since it's a fanfic about two Eevees, it might revolve around their evolution. Perhaps one Eevee has a strong desire to evolve into a certain form, like a Vaporeon because it loves the water, while the other Eevee is content with being just an Eevee for a while. The story could detail their journey towards or away from evolution. It could also include elements of the Pokemon world such as trainers, battles, and the search for rare items. There might be conflicts like rivalries with other Pokemon or misunderstandings between the two Eevees that they need to overcome.
Obviously, the foxes would be the main characters. There could be an old, wise fox that acts as Naruto's mentor among them. It could have a name like Kyo, and it would be the one to teach Naruto the most important lessons.
Gaara would be an obvious choice. Since Gaara is from Suna, he could be Naruto's close friend. They could train together and share their experiences of being jinchuriki. Kankuro and Temari might also become his friends. Kankuro could teach Naruto some of his puppet techniques, and Temari could help Naruto with wind - style jutsu training.
Sasuke could be one of his companions. Even though they've had their differences, they always end up coming together for big challenges. Sasuke's sharingan would be useful on the moon, helping them detect any hidden threats. Another could be Kakashi. His experience and knowledge would be invaluable in a new and strange environment like the moon. He could also teach Naruto and Sasuke new techniques based on the moon's conditions.