Obviously Naruto himself. Then Sasuke would probably be involved as they have a deep connection. Sakura too, since she's part of their team. Kakashi might also play a role as Naruto's former teacher.
Well, it could have Naruto coming back with new powers. Maybe he has some special jutsu he learned during his time away. It might also involve different relationships with the other characters, like a new bond with Sasuke or a changed dynamic with Sakura.
In some fanfictions, Naruto might return to Konoha to a cold reception because the villagers still hold grudges from his past. Maybe they haven't fully accepted his power or the chaos he sometimes brought. For example, they could be afraid of his Nine - Tails power flaring up again and causing destruction.
Definitely Hinata. Her love for Naruto is well - known. Sakura, too, as she has grown closer to Naruto over the years. Ino might also be in the harem. She has had her own moments with Naruto and her skills as a ninja could be an asset. And perhaps Karui from the Cloud Village. After Naruto's peace - making efforts between the villages, she could have developed feelings for him.
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.
Perhaps it could be someone from his own village that he never really noticed before. Like a girl who was always in the background but during his time away, she grew into a confident and beautiful woman. She could be someone who works in the hospital, and Naruto starts to see her in a new light when he comes back injured from a mission.
Kurenai might be a good sensei for Naruto's different team. Her expertise in genjutsu would be valuable. She could help the team develop their skills in this area, especially if the new team members have some potential in genjutsu. Kurenai is also very perceptive, which would be great for guiding Naruto and his new teammates through difficult situations.
In this fanfiction, the plot might involve Kushina coming back to help Naruto in his toughest battles. Maybe she uses her unique chakra abilities that Naruto has inherited to give him an edge. She could also provide emotional support, as Naruto has always longed for his mother.
Another theme is growth. Both Naruto and Hinata may have grown separately during Naruto's absence. When he returns, they have to adjust to the new versions of each other. For instance, Hinata might have become stronger in her own way, and Naruto has to recognize that.
Obviously, Kushina is one of the main characters. Naruto is also a central figure as her son. Since it's related to the Naruto universe, characters like Sasuke, Sakura, Kakashi might also be important in the fanfiction. They could interact with Kushina in various ways, like Sasuke might be skeptical of her at first, or Sakura could be eager to learn from her.