Sasuke could also appear in some fanfictions. Maybe he comes to visit Naruto in his isolated place, and they have a heart - to - heart talk that helps them resolve some of their past issues.
Iruka sensei might show up too. He was an important figure in Naruto's early life. In the fanfiction, he could be checking on Naruto secretly, leaving food or supplies outside his door, showing his continued care for Naruto even when he's living alone.
Obviously, Peter is the main character. There could also be his neighbors who might play a role. For example, an old lady next door who gives him advice or a young boy who is curious about Peter's solitary life.
Obviously Naruto himself is a common character. Sasuke might also be there, perhaps as a rival or an ally in this devil - infused Naruto's story. Kakashi could be around too, as a mentor figure trying to guide Naruto through his new, darker path.
Well, Naruto himself is obviously a common character. Sasuke also often makes an appearance, either as a rival still or as someone who has a change of heart and decides to join Naruto's training. Kakashi might show up too, to give some guidance or check on Naruto's progress.
The neighbors in general are also quite popular in fanfiction. There could be an older neighbor who is a retired artist. In fanfiction, this neighbor could start teaching Kotaro how to draw, which helps Kotaro express his feelings in a new way and also gives him a new hobby.
Hinata might show up as well. Her relationship with Naruto can develop in new ways in different dimensions. For instance, in a dimension where Naruto is in a more dangerous situation, Hinata's love and support could be a key factor in his journey.
Jiraiya often appears. Since he was Naruto's mentor, when Naruto travels back in time, Jiraiya can play an important role. He could be the one to initially believe Naruto's story about coming from the future. Another common character is Kakashi. Kakashi was Naruto's teacher and his presence in the time - travel story can add a lot of interesting interactions, like Naruto showing Kakashi things he wouldn't know yet in that timeline.
Sasuke is often a common character. He might have a different reaction to Naruto's banishment compared to the original story. Maybe he decides to join Naruto outside of Konoha or tries to find a way to get him back. Kakashi could also be there. He might be conflicted about Naruto's banishment and could play a role in either helping Naruto secretly or trying to uphold Konoha's decision.
Jiraiya could be another one. Since he was Naruto's mentor, he might go after Naruto when he's kicked out and continue to train him in secret.
Harry is the central figure for sure. Neville Longbottom could play a role. He might be one of the few who know where Harry is hiding and is trying to protect the trunk from being discovered. Hagrid could also be involved. He might bring Harry some food and supplies while he's in the trunk. And there could be some mysterious old wizard or witch who has some connection to the trunk and its magic.
Annabeth could be one of the characters. She might come to Tartarus to rescue Percy or be accidentally dragged in while trying to find him. Grover could also show up, using his nature - related powers to navigate the strange and dark environment of Tartarus. Another potential character could be Nico. Given his connection to the Underworld, he may be able to sense Percy's presence in Tartarus and come to his aid.