Well, one possible plot could be Naruto exploring the dangerous parts of the Forest of Death while forming an unexpected bond with another male character. Maybe they start off as rivals but gradually develop a deep emotional connection as they face the perils together.
It could be Sasuke. Since they have a complex relationship in the original series, in the yaoi fanfiction, their relationship could take a different turn in the Forest of Death. They might have more intimate moments while facing the challenges there.
I recommend the novel," The Touching Flower of Mo Shang." The heroine of the story appeared in the bamboo forest. She was dressed in white and had the Phoenix Whip. This novel described the encounter between the female lead and the male lead, Leng Mingye, in the bamboo forest. I hope you will like this novel!
Maybe Harry discovers a hidden magical community in the forest. He could learn new spells from the forest creatures and use them to protect Hogwarts later.
I'm not sure specifically as there could be many different takes in such a fanfiction. It might be about Naruto having some special connection to the birth of a forest, perhaps he discovers a new jutsu related to forest growth or there could be a spiritual element where he communes with the forest's essence.
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.
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.
Obviously Naruto would be the main character. There could also be the forest spirits which could be original characters created for this fanfiction. Maybe some of Naruto's friends like Sasuke or Sakura might make an appearance, either to help Naruto in his forest - related challenges or to try and bring him back to the village if they think he's spending too much time in the forest.