There are numerous possibilities. Naruto could have explored more of the ninja world outside of the Hidden Leaf. He may have made new alliances with other villages. His character could have matured further, and his dreams for the ninja world might be closer to realization. He could also be facing new personal challenges that test his growth over the past three years.
A 'Naruto After Death' fanfiction could show Naruto's journey in the afterlife as a way to bring peace to the souls of those who died with grudges. He could use his unwavering will and the bonds he formed in life to help resolve the negative emotions of these lost souls. He might also meet his parents in the afterlife and finally have a proper family time that was cut short in his living days.
In this fanfiction, Naruto might be on a mission to find Kakashi for some crucial training. Maybe he wants to learn a new jutsu that only Kakashi can teach him.
They could face a lot of opposition. In the Naruto world, Naruto has his own set of friends and allies, and Guren is from a different group. Their kiss might lead to conflicts between different factions. For example, Naruto's friends might not trust Guren immediately, and Guren's side could also have issues with her getting involved with Naruto.
In such a fanfiction, Naruto might return to the village with new and powerful jutsu. He could surprise his friends with his enhanced skills. For example, he might be able to create new types of shadow clones or have a better control over his chakra. Maybe he would also have new insights on how to deal with his enemies, like Orochimaru or the Akatsuki.
Well, he might start showing his true strength more openly. Maybe he won't hold back in battles as he used to. He could also be more assertive in his relationships with his friends and mentors.
In some fanfictions, Naruto and Sakura might start to realize their true feelings for each other. They could go on adventures together, exploring the world that has been changed by the war. Maybe they would start a new life in a rebuilt village, sharing their experiences and growing closer day by day.
Well, they might start to build a relationship based on mutual respect. Naruto, having just come out of the war, could see Temari in a new light. Maybe they'll go on missions together and gradually fall in love.
In this kind of fanfiction, Naruto might be welcomed as a hero. The village could start to rebuild with his leadership. People would look at him with newfound respect and admiration.
Well, they might start building a family. After the war, Naruto and Hinata could finally have the peace they deserve to focus on their relationship. They could have a small, simple wedding and start living together in Konoha.
Naruto may also try to make the ANBU laugh. He could tell some of his silly jokes or funny stories from his adventures. Laughter is a great way to relieve stress, and in the context of this fanfiction, it would help the ANBU to relax after a difficult mission. For example, he could tell the story about when he accidentally turned into a girl due to a jutsu gone wrong and the hilarious situations that followed.