One possible plot could be Naruto dying heroically in a battle and coming back as a ghost to guide his friends. For example, he could help Sasuke understand the true meaning of friendship from beyond the grave.
Well, it could make the plot more complex. For example, he might discover secrets that others can't. Maybe he'll find out some hidden pasts of the village or certain characters. Ghosts could lead him to new quests or help him understand some old mysteries better.
There could be the ghost of the First Hokage. He might have some important wisdom to pass on to Naruto. Maybe the ghost of a fallen comrade who has some unfinished business or a message for Naruto.
The plot might involve Naruto seeing his old friends again in a different context. For example, they all end up in a parallel dimension where they have to work together to get back to their own world. Along the way, Naruto gets to reunite with characters he thought he'd lost forever. They face various challenges in this new dimension, like strange creatures and difficult terrains. Naruto's determination to see his friends again and return home drives the story forward.
In this fanfiction, perhaps Hinata sees a future full of danger for Konoha. She then has to figure out a way to prevent it, with Naruto by her side. It could be that they face new and powerful enemies that they've never encountered before. She might see different possible outcomes depending on the actions they take in the present.
Well, they might see a future where they have a big family. Since Naruto always wanted to be acknowledged and have people around him, he could see himself surrounded by his children and Hinata in a happy home. And for Hinata, she might see herself as a strong kunoichi, still supporting Naruto in his Hokage duties.
He could interact with his old sensei, Iruka. Iruka was an important figure in Naruto's life, and as a ghost, Naruto might visit Iruka to give him some comfort or to seek advice. Since Iruka was always there for Naruto when he was alive, their connection could still exist in the afterlife.
One possible plot for 'naruto becomes a ghost fanfiction' is that Naruto sacrifices himself to save the village. As a ghost, he discovers new abilities like being able to possess people or objects. He uses these powers to protect Konoha from threats that the living ninjas can't handle. He might also have to deal with his own unfulfilled desires and relationships in this new ghostly form.
In a 'naruto is half ghost' fanfiction, the plot might center around Naruto's struggle with his dual nature. He could be shunned by some in the village who fear his ghostly side. Meanwhile, he has to learn to control his new powers. For example, he might discover he can travel to a spirit realm and has to figure out how to use that to his advantage, like getting intel on enemies or finding lost jutsu.
Well, it could be that Naruto's friend from another village, who has been like a brother to him, has to go back to his own village for good. Naruto, being the emotional and kind - hearted person he is, decides to sing 'See You Again' at the border as a way to say goodbye. This song could also symbolize the hope that their friendship will endure despite the distance. And during the singing, there could be some emotional exchanges between Naruto and his friend, like promises to visit each other in the future.