Well, there could be a fanfiction where the Nine - Tails Chakra has a mind of its own and starts to communicate with Naruto in a more complex way. It could show him visions of the future of the ninja world and guide him to make choices that are different from what he would have done otherwise. This could lead to new alliances and a completely different path for Naruto and his friends in the story.
You could create a character who is a descendant of an ancient clan that has a special connection to the Nine - Tails Chakra. This character could be a rival to Naruto at first, thinking that Naruto doesn't deserve the power of the Nine - Tails. Another option is a mysterious healer who can manipulate the Nine - Tails Chakra in a unique way to heal even the most severe wounds.
One interesting way is when Naruto absorbs chakra through his shadow clones. In some fanfictions, the clones can be used not just to gather information or attack, but also to absorb the chakra of the opponents they interact with. Then, they transfer this absorbed chakra back to Naruto, making him more powerful.
Perhaps there is an ancient artifact or a powerful curse that causes Naruto to absorb all chakra. In the fanfiction world, it's common to introduce such unique elements. For example, he might find a magical scroll that, when opened, starts sucking in all the chakra in the vicinity and then channels it into Naruto. Or it could be a curse placed on him by an enemy, but instead of harming him, it gives him this strange power to absorb all chakra.
The consequence might also be a shift in the balance of power in the Naruto universe. With all that chakra, Naruto could potentially change the political situation. He could end wars single - handedly or force the different ninja villages to re - evaluate their strategies. Moreover, his own physical and mental state might be affected. There could be a struggle within him to keep his identity intact while dealing with such an overwhelming power source.
He could share it with Hinata. Given their relationship, Naruto might transfer some of his chakra to Hinata to protect her during a dangerous situation. This would also strengthen their bond further in the 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.
Well, Naruto could also turn to his friends for help. In the Naruto universe, teamwork is highly emphasized. His friends like Sasuke, Sakura, and others have their own unique abilities. They could cover for Naruto's lack of chakra and together they could come up with strategies to fight opponents. Maybe Sasuke could use his Sharingan and ninjutsu skills, while Sakura could use her medical and combat skills to support the group.
One possible reason could be some kind of strange chakra infusion. Maybe he comes into contact with a powerful and mysterious chakra source that mutates his body in a way that causes tails to grow. Another reason might be related to some ancient curse or prophecy. It could also be the result of a new jutsu he attempts that goes wrong and has unforeseen physical consequences.