There could be a new group or organization introduced in the fanfiction specifically because of Naruto's Mokuton awakening. They might be jealous of his power or fear it, and thus become antagonists. They could be a group of rogue ninjas who want to steal the Mokuton ability from Naruto for themselves and use it to take over the ninja world.
The Akatsuki members could also be antagonists. Since Naruto has a new and powerful ability, they might see him as a key target. For instance, Pain might view Naruto's Mokuton as a threat to his plans of world domination and try to eliminate him.
One potential antagonist could be Orochimaru. He might be interested in Naruto's Mokuton powers for his own evil experiments. He could try to capture Naruto to study how he awakened the Mokuton and use that knowledge for his own gain.
The Akatsuki could be potential enemies. They might see the Mokuton Prodigy as a threat or a valuable asset to capture. Their diverse powers and motives would make for interesting confrontations with the prodigy.
Another potential character could be a new, original character created specifically for the fanfiction. This character could be a young ninja who discovers they have an affinity for the Mokuton Sage powers and has to learn to control and use them while facing various challenges in the Naruto universe.
One possibility is that there's some ancient chakra or energy in Wave that interacts with Naruto's own chakra. The unique environment of Wave, with its water and nature elements, might have caused his Mokuton to awaken. Another reason could be that Naruto has some kind of connection to the First Hokage that gets revealed during the Wave mission, and that connection enables the Mokuton awakening.
One potential antagonist could be a rogue ninja who also has aerokinesis but uses it for evil. He might be jealous of Naruto's natural talent and try to undermine him at every turn. Another could be a powerful sorcerer from a far - off land who has come to the Naruto universe specifically to find someone with aerokinesis to either steal their power or use them as a tool. There could also be a group of anti - ninja who see Naruto's new power as a threat to their plans of overthrowing the ninja system and they try to eliminate him.
A potential main character could be a long - lost relative of Hashirama who has the mokuton ability but has been neglected in the main Naruto story. This character could then embark on a journey to discover their true power and place in the ninja world.
Perhaps Orochimaru could still be an antagonist. In this fanfiction, he might be jealous of Naruto's new god - like gaming powers and try to steal them for his own experiments.
There could be a jealous fellow ninja from within the village who feels that Naruto is getting too much attention for his blade - mastery. This ninja could turn against Naruto and become an antagonist, perhaps even teaming up with external forces. Also, an ancient evil entity that was sealed away long ago might be awakened by the power of Naruto's blade and seek to destroy him and the village to regain its freedom.
There could be new antagonists created specifically for this fanfiction. Maybe some other ninja from a far - off land who are jealous of Naruto's power. They could come to the Hidden Leaf Village to challenge Naruto and steal his speed - related secrets.
The villagers themselves could be antagonists in a way. Their fear of Naruto's 'demon' side might lead them to try and ostracize or even harm him.
A group of rogue ninjas who have made the island their base could be antagonists. They might see Naruto as a threat to their operations on the island.