A new character could be introduced as a rival. Maybe a rogue ninja from a far - off land who also has a powerful dojutsu and sees Naruto's Rinnegan and position as Hokage as a threat to his own plans for power. This character could constantly try to undermine Naruto's rule and steal his Rinnegan powers.
It could be a rogue ninja who was once a part of Konoha but was banished for unethical experiments. Now, with a thirst for revenge against Naruto and the village, he returns as a powerful and unpredictable foe.
Sasuke could be his rival. Sasuke is known for his competitiveness and would see Naruto's entry into the Need for Speed world as a challenge. He would use his Sharingan to analyze Naruto's moves and try to outdo him on the race track.
It could be a new character, a rogue ninja from a long - lost clan. This antagonist might have a vendetta against Naruto because they see his potential to awaken the Rinnegan as a threat to their own plans for power. They could be trying to stop Naruto from achieving this new level of power so that they can carry out their evil deeds unopposed.
Sasuke could potentially be an antagonist. With Naruto having the Rinnegan, Sasuke might see him as a threat to his own power and goals. This could lead to a new rivalry between them, different from their previous one.
Obviously, the new Hokage would be one of the main characters. It could be a character we already know like Naruto's son, who has inherited his father's determination and strength.
Gray Fullbuster could be a great rival. Gray is a powerful ice - make mage. His calm and collected demeanor would contrast with Naruto's more exuberant personality. Gray's precise and powerful magic attacks would pose a serious threat to Naruto, forcing him to come up with new strategies using his ninja skills.
It could be a new character created specifically for the fanfiction. This character could also be a seal master or have some special skills related to seals that directly oppose Naruto's. They might have a personal vendetta against Naruto or be from a rival village, and their encounters during the Chunin Exams would be filled with high - stakes battles and intense rivalry over seal - related matters.
Sasuke could be an alternative. He has strong ninja skills and a deep understanding of the ninja world. His experiences have made him grow into a very capable person, and his Sharingan gives him an edge in combat and strategic planning.
One possible main antagonist could be a rogue ninja who also has a connection to the Mokuton or Rinnegan powers. Maybe he was once part of a secret experiment that went wrong and now he wants to take Naruto's powers for himself. Another option could be an ancient being that was sealed away long ago and is now awakened by Naruto's new powers. This being could see Naruto as a threat to its plans of world domination.
It could be a new character who is jealous of Naruto's newfound power of the Rinnegan. Maybe someone who has been in the shadows all along and now sees Naruto as a threat to their plans for world domination.