Naruto could meet his mother, Kushina. She could comfort him and share more about his family's past that he didn't fully know in life. Also, he might encounter villains like Madara. But instead of fighting, they could have discussions about the cycle of hatred and how it could have been broken. This would be a very interesting encounter as it could lead to new understandings for Naruto.
In such a fanfiction, Naruto would most likely meet Sasuke if Sasuke passed away before or at the same time as him. Their bond was so strong that it would be natural for them to reunite in the afterlife. They could reflect on their relationship, from being rivals to friends, and how they influenced each other's lives. It would be a very emotional reunion.
He might meet his sensei, Jiraiya. They could have long talks about Naruto's growth as a ninja and Jiraiya could give him more wisdom from the afterlife perspective.
He would most likely meet his father, Minato Namikaze, and his mother, Kushina Uzumaki. These are the two main family members he never really got to know growing up.
There could be a group of kids on the beach who are inspired by Naruto. They might approach him and ask for autographs or to show them some ninja moves. Naruto would be happy to oblige and in the process, he could discover a new talent among the kids that could be important for the future of the ninja world.
He might meet an old acquaintance who is also alone. They could share their stories and perhaps find some comfort in each other's company.
Maybe some local tribespeople who have unique abilities or knowledge. For example, they could teach Naruto some ancient techniques or survival skills that are not known in the Hidden Leaf Village. There might also be wandering samurai or other shinobi from different regions who pass by the outpost and interact with Naruto.
Naruto might run into a group of rogue ninjas who are using the bunker as their hideout. This would lead to a confrontation where Naruto has to use his skills to defeat them and protect the village from their potential threats.
He could meet the Raikage. The Raikage might be initially skeptical of Naruto but could later see his potential. There are also other strong ninjas in Kumo like Killer Bee. Naruto might cross paths with him and they could have some interesting interactions, perhaps even training together.
In this fanfiction, Naruto might run into Arthas Menethil before he fully turned into the Lich King. It would be a very different kind of encounter compared to what he's used to in his own world. He could also meet Uther the Lightbringer. Uther might be curious about Naruto's unwavering will and Naruto could be in awe of Uther's connection to the Light. Additionally, he could meet many of the adventurers and common folk in Azeroth, each with their own stories and skills.
Naruto could meet some young and upcoming Iwa ninja trainees. They might be curious about Naruto and his abilities from Konoha. These trainees could either look up to Naruto or be jealous of his fame, leading to various interactions. Also, there could be some old - timer Iwa ninjas who remember past events involving Konoha and have their own views on Naruto's presence in Iwa.
Naruto might meet Itachi in heaven. Itachi could finally reveal all the secrets and the true intentions behind his actions to Naruto. And they could become true friends without any misunderstandings. Additionally, Naruto could also meet Neji, and they would talk about how the ninja world has changed since Neji's sacrifice.
Naruto could also meet the previous Hokages in their prime. He could learn from them directly and perhaps even influence their decisions. For example, he might be able to convince the First Hokage to handle the Uchiha clan's situation differently, which could have a huge impact on the future (or in this case, the future that Naruto comes from).