Another option for the main antagonist could be a power - hungry shinobi from another village. They hear about Naruto's new and strange power of the chakra chains and decide to capture Naruto to study and steal the power. They might have a group of highly skilled ninjas working for them and use underhanded tactics to try and get to Naruto.
It could be a rogue ninja who is also after the power of the chakra chains. This ninja might see Naruto as a threat and try to eliminate him to get the chains for himself.
Perhaps the origin of the chakra chains lies in Naruto's connection to the tailed beasts. Since he has a unique bond with the nine - tailed fox, the chakra chains might be a manifestation of that bond, combined with his own latent Uzumaki powers. It's possible that as he grew stronger and his understanding of chakra deepened, this ability was awakened.
It could be a jealous ninja from another village who sees Naruto's infinite chakra as a threat to their own village's power. This ninja might try to steal Naruto's chakra source or find a way to nullify it.
Maybe it has something to do with his Uzumaki heritage. The Uzumaki clan was known for their strong chakra, so it could be a latent ability passed down through the generations.
The main antagonist could be a group of dark wizards who are trying to revive an ancient and powerful dark magic. They believe that Draco has some information about it because of his family's past associations. So they chain him up to force him to talk. This group could be led by a mysterious figure who has a personal vendetta against the Malfoy family.
It really depends on the specific fanfic. But it could be Naruto himself, as he often has new abilities or storylines in fanfics. He might be the one to master the chakra chains in a unique way.
In many fanfictions, the Rinnegan and chakra chains are often intertwined in terms of power and function. The Rinnegan, being one of the most powerful ocular abilities in the Naruto universe, can potentially bestow special properties on the chakra chains. The chakra chains themselves might be a way to channel the raw power of the Rinnegan. For instance, they could be used to bind opponents while simultaneously draining their chakra through the Rinnegan's absorptive capabilities. This connection adds an interesting dynamic to the characters who possess both the Rinnegan and the ability to use chakra chains, making for some really cool and unique battle scenarios in fanfiction.
One implication could be that Naruto becomes more powerful in combat. The chakra chains can be used as a weapon or a form of defense, allowing him to hold opponents in place or deflect attacks.
Perhaps Naruto unlocks the chakra chains because of a special item he discovers in Wave. This item could be something that has a connection to his past or to the chakra chains themselves. It might emit a certain energy that interacts with Naruto's chakra, causing the chains to be unlocked. Another possibility is that Naruto's encounter with the local chakra environment in Wave is different from what he's used to in Konoha. This new environment could act as a catalyst, triggering a reaction in his chakra system that results in the unlocking of the chakra chains.
The golden chakra chains in fanfiction are often seen as more powerful. Regular chakra chains are already a formidable ability, but the golden ones might have enhanced strength, allowing Naruto to break through stronger defenses or hold more powerful foes. They could also have different properties, like being able to disrupt an opponent's chakra flow more effectively.
A simple way would be to have a character inherit both traits. For instance, if Naruto and Sasuke had a child in the fanfiction, that character might inherit the Uzumaki's chakra chains ability and the Uchiha's Sharingan. The story could then revolve around this character learning to master these powers and facing various challenges.