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.
Naruto's reaction would be a mix of curiosity and caution. He would be curious to explore the contents of the Bingo Book, looking at the profiles of different ninjas. However, he would also be cautious because he knows that having this book could make him a target. He might also feel a sense of responsibility, thinking that he has to protect the information in the book from falling into the wrong hands. He may even try to find out how the Bingo Book is updated and who is in charge of it, so that he can understand the system better and use it more effectively.
In some fanfictions, Naruto getting in the Bingo Book could lead to a change in his relationships. His friends might be more worried about him and try to protect him even more. For example, Sasuke could become more determined to keep Naruto safe from those who would harm him because of his new status in the Bingo Book. Also, the village might have to take extra precautions to keep Naruto hidden or use him as a sort of decoy in strategic battles.
In a fanfiction where Naruto is in the Bingo Book, it could mean that the ninja world's perception of him has drastically changed. Maybe he's been framed for a serious crime he didn't commit. This would lead to him trying to clear his name while also avoiding those who are after the bounty on his head. He'd have to rely on his friends more than ever, and there would be a lot of tension between him and the ninja villages that are now after him.
Kakashi could be a popular character in these fanfictions too. Given his skills and his mysterious past, he could be involved in various Bingo Book - related scenarios. For instance, he might be the one assigned to track down a particularly dangerous ninja on the Bingo Book list. His calm and collected demeanor in the face of danger would add an exciting element to the story.
In some Naruto Bingo Book Fanfiction, we might see a story where a group of lower - level ninjas decide to team up to take on the powerful targets in the Bingo Book. They train hard, develop new techniques, and against all odds, manage to defeat some of the more feared individuals in the Bingo Book. This shows how determination and teamwork can overcome even the most difficult of obstacles in the Naruto universe.
Well, he might discover some interesting information about his enemies or other ninjas in the Bingo Book. Maybe he'll be shocked to find out details about certain characters he thought he knew.
Perhaps a plot where Naruto uses his status in the bingo book to his advantage. He could be luring out certain enemies who underestimate him, thinking they can easily capture him. His ninja skills would then be put to the test in unique ways.
Maybe it's a powerful enemy from outside the village who has infiltrated the bingo book system. They see Naruto as a major threat to their plans and so secretly added him to the book, so they can send their minions to take him out without raising too much suspicion.
Well, one possibility could be that Naruto has some sort of hidden power or ability that the bingo book writers discovered and added him secretly. Maybe it's a power he doesn't even know he has yet. It could lead to all sorts of interesting situations like other ninjas being sent to hunt him down without him fully understanding why.