Obviously Naruto would be one of the main characters since he is the one writing the book. His friends like Sasuke and Sakura would also likely be important characters as they have been part of his life journey.
Since we have no details about the book, it's impossible to say for sure who the main characters are. It might be that Arthur writes a story about some new characters he has imagined, like a group of space explorers or a family of friendly monsters. But again, this is just guessing without more information about the book.
There could be many different fans who write it. It might be an amateur writer who just loves Naruto and wanted to explore this unique scenario.
It could be about Naruto writing a book that details his adventures and the lessons he's learned. Maybe he writes about his friends and how they all grew together.
It's hard to say for sure as it's fanfiction, but it could feature Naruto himself. He might be on a journey to understand the secrets of the book of the dead. Sasuke could also be involved as he often gets involved in Naruto's important quests. Maybe even Kakashi could be there, guiding the younger ones with his wisdom about the strange new elements introduced by the book of the dead.
Well, Naruto is surely one of the main characters as the title implies it's centered around him. His friends like Sasuke and Sakura are likely to also be important characters, as they are usually involved in Naruto's adventures.
Since it's fanfiction, the main characters could be the usual Naruto favorites like Naruto himself, Sasuke, or Sakura. But it could also introduce new characters created by the fanfiction author who play important roles related to chakra.
Naruto for sure, but also characters like Kakashi. He's very intelligent and adaptable, so he would be great in a modern warfare setting. Sakura could also be a main character. She has medical skills which could be very useful in treating modern - warfare - related injuries. And don't forget about Shikamaru. His strategic mind would be invaluable in military operations.
Obviously, Naruto and Moana would be the main characters. They are from their respective universes and would be the ones driving the story forward in a crossover. Their different personalities and abilities would create interesting interactions.
Well, Naruto and John Carter are the must - haves. But in addition, Tars Tarkas from the John Carter world could also be a main character if he somehow ends up in the Naruto world. His unique appearance and honor - bound nature would make for an interesting addition. And from the Naruto side, Sasuke could be a key character. He might initially be suspicious of John Carter but later come to respect him and work together in some battles.
Obviously Naruto would be one of the main characters. He's the protagonist of the Naruto series, so he'd likely be at the center of the action in this fanfiction too. He'd be using his ninja abilities to combat the threats in the high - school - turned - zombie - land.