There could also be a power - hungry individual within the village itself in the future. This person might see Naruto and Hinata as threats to their own rise to power. So they start creating problems for them, trying to turn the villagers against Naruto and Hinata.
Maybe an old enemy who somehow managed to survive and has been plotting revenge all this time. This enemy could have found a way to travel through time as well and is now causing trouble in the future. They might have new powers or allies that Naruto and Hinata have to figure out how to deal with.
It could be some new group that emerged due to the changes in the ninja world over time. They might oppose the way Naruto and Hinata's village is being run and want to impose their own ideals.
Another type of antagonist could be a strict professor who doesn't like Naruto's carefree attitude and Hinata's association with him. The professor might try to give them a hard time, like assigning them extra difficult projects or being overly critical in class, which becomes an obstacle in their college life and relationship.
It could be some rogue ninjas who are against Naruto's new peaceful policies as Hokage. They might see Hinata as a weakness to be exploited to get to Naruto.
One possible antagonist could be a jealous student. Maybe someone who has a crush on Hinata and doesn't like Naruto getting close to her. This student could try to sabotage their projects or spread false rumors about them at the academy.
In this fanfiction, they might see a more advanced Hidden Leaf Village. Maybe there are new jutsus and technologies. For example, the village could be protected by some high - tech barriers instead of just the traditional ninja guards.
One possible plot could be that Naruto and Hinata face a new threat to the Hidden Leaf Village. They have to work together, with Hinata using her Byakugan skills to detect the enemy's movements and Naruto using his Nine - Tails chakra for powerful attacks. Along the way, they also focus on raising their family, teaching their kids the importance of ninja values.
It could be some of the old - school ninja clans who are against the new order Naruto and Hinata are trying to establish. They might see their rule as a threat to their traditional power and influence.
Maybe Orochimaru's former followers who are still lurking in the shadows. They see Naruto as a threat and Hinata as an easy target to get to Naruto. Another possibility could be some power - hungry shinobi from other villages who view Konoha as weak after the Pain incident. They might target Naruto and Hinata as key figures in Konoha's future to try and undermine the village's rebuilding efforts.
One possible antagonist could be Orochimaru. He's always been interested in powerful and unique abilities. Naruto's new powers as the son of doomsday would be very appealing to him, and he might try to capture Naruto to study or steal his powers.
In this fanfiction, it's possible that an ancient and powerful beast is the antagonist. The beast might have captured Pyraa to lure Naruto into a trap. Naruto will need to use all of his skills, including his Sage Mode if necessary, to defeat this beast and save Pyraa.
There could be a secret organization that has managed to turn the world against Naruto. This organization could be made up of rogue ninjas or people with a vendetta against the Uzumaki clan. They might spread false rumors or manipulate events to make Naruto look like a villain. Another possibility is that some of the old - school shinobi leaders who are afraid of change and Naruto represents a big change in the ninja world, so they oppose him.