Bella Swan is a very likely character. Since she has such a strong connection to Forks, which is her home in the Twilight world. Her journey home could be filled with thoughts of Edward and the vampires she has come to know.
Another possibility is that the fanfiction could introduce new characters who play a major role in the 'coming home' story. They could be new vampires or humans who have a connection to the original Twilight characters. For instance, a new vampire who was turned while Bella was away and now she has to deal with this new presence when she comes home, and this new character could bring a whole new set of conflicts and relationships into the story.
Edward and Bella are likely to be main characters. Since they are central to the 'Twilight' story, in a fanfiction about a living will, they could be involved in making decisions regarding the living will, perhaps related to their future together or the safety of their family.
Maybe an old storyteller who has a deep connection to the area with the cracked pavement and during twilight shares tales of the past with the younger generation. There might also be a group of friends who use the cracked pavement as their meeting place at twilight, and they get into all sorts of adventures together.
Perhaps it's about one of the werewolves going back to their reservation. They might be reflecting on how their life has changed since the appearance of the vampires in the area. For example, Jacob could be on a trip home and thinking about his complex relationship with Bella and his pack.
The main characters would definitely be Marinette and Adrien. Marinette, who is Ladybug, would be a central figure as she tries to balance her normal school life during the trip with her superhero duties. And Adrien, as Chat Noir, would be there to support her and also have his own storylines, like dealing with his overbearing father's restrictions even during the trip.
Jiraiya could be another main character. He is Naruto's mentor, and it's very likely that he would accompany Naruto on this serious training trip. Jiraiya's vast knowledge and experience would play a crucial role in Naruto's growth during the journey.
Sakura would be very likely to appear. She's Naruto's friend and has always been an important part of his life in Konoha. Kakashi too, as Naruto's former sensei. He would be interested in Naruto's growth and return. His friends like Shikamaru, who is smart and has always been there for Naruto in different situations. And of course, Iruka - sensei, who was like a father figure to Naruto in the beginning. He would be overjoyed to see Naruto come back home.
It's likely that Bella and Edward could be main characters. Since it's a Twilight fanfiction, they are central to the original story. And with the theme of 'broken hearts', their tumultuous relationship could be a focus. Maybe they are on a journey along the highways, either physically or in their relationship, and facing heartbreak.
Naruto and Bella could be an interesting pair. Naruto's energetic and positive nature could contrast with Bella's more introverted and moody self. It could create a unique dynamic where Naruto tries to cheer up Bella and she, in turn, shows him the more complex emotional side of the Twilight world.
Obviously, Edward himself is a central character as he is the one being wrongly blamed. Bella would also be involved as she is closely associated with Edward in the Twilight series. His vampire family, such as Alice, Jasper, Emmett, Rosalie, Carlisle and Esme, would likely be part of the story too. They would either be trying to help him clear his name or be affected by the false blame in some way.