Rock Lee would be a great addition. His high energy and intense training regime could translate well into the world of dance. He would be the one pushing everyone to practice harder and would come up with some really unique and physically demanding dance moves. He could also have some friendly rivalries with other dancers in the fanfiction.
Sakura could be a main character. She could be the one who encourages Naruto to get into dance in the first place. Maybe she has a secret love for dance and wants to share it with Naruto. She could also use her medical ninjutsu knowledge to help prevent dance - related injuries within the group.
Ino could be a main character too. She could use her mind - control jutsu in a creative way during dance battles. For example, she could make the opponents think they are seeing double or make them misstep slightly. Also, she would be very stylish and help design the costumes for the dance group, adding her own fashionable touch to the 'Naruto x Step Up' fanfiction.
Well, there could be an old butler who has been in the household for decades. He initially doubts Naruto's abilities but later becomes his mentor. And then there could be a group of thieves who target the wealthy household. Naruto has to use his butler skills and ninja skills to fend them off. And perhaps a childhood friend of Naruto's who visits him at the butler job and is amazed at how he has changed.
Boruto is often a popular character in such fanfiction. Since he also has the Jougan, stories might focus on his training with Naruto to master this power. Their father - son relationship can be explored in new ways as they both deal with the implications of the Jougan.
Well, obviously his sister would be a main character. She could be someone with a very different personality from Naruto. Maybe she's more introverted and focused on her studies or training in a very solitary way. Another character could be Naruto's mentor, like Iruka. He might be one of the few people who actually notice Naruto's struggle of being ignored because of his sister, and try to encourage Naruto in his own way.
Definitely the Kumo ninjas who carry out the kidnapping. There could be some well - known Kumo characters like Killer Bee. He might be involved either directly in the kidnapping (unlikely as he is more of a good guy in the original) or in the events that follow. Another character could be the Raikage. He may or may not be aware of the kidnapping depending on the plot. If he is aware, his actions and decisions would play a major role in how the story unfolds.
Sasuke is often a common character. He might be initially suspicious of Female Naruto, thinking she could be a threat to Naruto or the village. But as the story progresses, he could end up being an ally and even help in their adventures.
Sasuke could be one of the main characters. He might initially be skeptical about Naruto's plan to rebuild Revan's army but later come around and offer his skills. Another could be Kakashi. His experience and wisdom would be valuable in guiding the new recruits. Sakura too, with her medical skills, could play an important role in taking care of the army members during battles and training.
Sasuke from Naruto could be a great addition. His brooding nature and powerful ninja skills would contrast well with Musubi's more upbeat and energetic personality. Also, Konohamaru could be included. He looks up to Naruto and his presence could add some humor to the story as he tries to impress Naruto and Musubi.
Sakura could also be present. She might be observing the training and learning some things herself, or she could be helping Kakashi in some way, like providing medical support during intense training exercises.
Kabuto is also common. He was Orochimaru's right - hand man. In fanfiction, he could be used to either further Orochimaru's plans against Naruto or he could have a change of heart and help Naruto against Orochimaru. His medical skills and knowledge of Orochimaru's secrets make him an interesting addition to the story.
Sasuke could be a great main character in such a fanfiction. He has a deep connection with Naruto. If Naruto's dying will flame is involved, Sasuke might be on a journey to understand what Naruto left behind and how to carry on his legacy. He could be conflicted between his own past and the new responsibility that comes with the dying will flame.