One possible origin could be a new type of training he undertakes. Maybe he discovers a hidden scroll that teaches him a unique form of physical conditioning that gives him super strength.
His super strength in fanfiction could also be a result of his own evolution as a character. As he faces more and more difficult challenges, he unlocks new levels of power within himself. This could be related to his growth as a ninja, his understanding of the ninja way, and his ability to tap into deeper reserves of chakra. It might also be that he inherits some latent strength from his Uzumaki lineage that only manifests in the fanfiction's unique storyline.
Often, it stems from his demigod heritage. In fanfic, just like in the original stories, his being a son of Poseidon can be the main reason for his super strength. It's a power that comes with his divine blood.
One possible origin could be a secret scroll he finds. Maybe it was hidden by an ancient shinobi who had the power to summon ravens, and Naruto stumbles upon it during one of his adventures.
One possible origin could be a long - lost kekkei genkai. Maybe Naruto's family had a secret bloodline ability that was suppressed for generations, and now it resurfaces as the red chakra.
In fanfiction, the chained blades could have various origins. One possibility is that they are a family heirloom that Naruto discovers. Maybe they were passed down from an unknown branch of his family. Another idea is that he finds them during a mission in some ancient ruins. The blades could be tied to a long - forgotten ninja clan that once had great power.
It could be due to a unique training method. In fanfiction, perhaps Naruto discovered a new way to purify his chakra through intense meditation or some sort of elemental training that no one else has tried before.
One consequence could be that his friends and allies start to see him in a different light. They might be in awe of his new power, which could create a bit of a distance between them at first. For example, some of his less - powerful friends might feel a bit inferior or intimidated.
In some fanfictions, Naruto might obtain super strength through special training. For example, he could be pushed to his limits by a new and powerful mentor who has unique training methods. This could involve extreme physical and mental challenges that force his body and chakra to evolve in ways that give him super strength.
Naruto's super speed and strength in fanfiction can vary widely. His speed might be enhanced to the point where he can move faster than lightning in some stories. His strength could be such that he can lift mountains. There was this one fanfiction where Naruto's new - found speed and strength were the result of a special training regime he underwent. He used his speed to dodge enemy attacks that were too numerous to count and his strength to defeat a powerful enemy who was thought to be invincible.
Well, in some fanfictions, Naruto's water - controlling ability could be a gift from a powerful sage. This sage, seeing Naruto's potential and his need for new powers to face upcoming threats, bestows upon him the ability to control water. Another origin could be that Naruto accidentally absorbs the chakra of a water - using enemy during a battle, and this chakra somehow melds with his own, giving him the power to control water.
One possibility could be some sort of new training he undergoes. Maybe he discovers a hidden jutsu scroll that teaches him how to control and produce fire from within his body. This could be a long - lost technique from an ancient ninja clan.