The main characters could be the new generation of ninjas like Boruto, Sarada, and Mitsuki. They are at the center of a new era in the shinobi world. But also, the old generation like Naruto, Sasuke, and Sakura would still be important. They could be guiding the new generation, and their experiences from the past would be crucial in dealing with the new challenges. For instance, if there is a new threat that has some connection to the past battles, the old generation's knowledge would be vital in fighting it. And the relationships between these two generations would be an interesting aspect to explore in the fanfic.
Obviously, Naruto himself would still be a main character, as he is now an important figure in the village. His son Boruto could also be a main character, as he might be following in his father's footsteps. And Sasuke would likely still play a significant role, perhaps as a mentor to the new generation.
It could be the original characters from the source material who have now aged 19 years. Their personalities might have changed a bit due to life experiences, but they still carry the essence of who they were.
It could be the original main characters from the source material, just older and more experienced. For example, if it's a fanfic based on a teen drama, the once - young protagonists are now adults with more responsibilities.
The main characters would likely be Callie and Arizona. They are the core of the 'calzona' concept.
Definitely Naruto himself. He would be an important character as the story is about his return after 20 years. His son or daughter could also be main characters, as they might be involved in the events related to Naruto's return.
The children of Harry, Ron, and Hermione would likely be main characters. For instance, Harry's son could inherit his father's courage and be at the center of a new mystery. He might have to deal with the high expectations placed on him because of his father's legacy.
The main characters could be Ladybug and Chat Noir, who are now experienced heroes. However, the fanfiction could also focus on a new group of heroes that they are training. These new heroes could come from different backgrounds and have unique personalities. There might also be some characters from the past that have turned into antagonists due to some past grudges or misunderstandings. And of course, the Kwamis would still be there, guiding the new and old heroes alike.
Hermione Granger would be a likely main character. She has always been a central figure. Maybe she's working on some revolutionary magical research or is involved in political reforms in the wizarding world. Her relationship with Ron and their family life could also be part of the story.
Obviously Danny Phantom himself would still be a main character. His friends like Sam and Tucker would likely also be important. They've probably grown and developed new skills over the 10 years.
Most likely the children of the main characters from the original series. Like James, Albus, and Lily Potter. Also, the kids of Ron and Hermione, like Rose and Hugo.
A detective who has been working on a cold case for 20 years and finally gets a breakthrough.