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 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.
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 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.
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.
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.
It could be from some sort of ancient ninja training that was lost and he somehow discovers it. Maybe there's a hidden scroll or a hermit who teaches him this fire - controlling ability.
The origin of Naruto's starfire powers in fanfiction might be due to an experiment. Some rogue ninja or a secret organization could have been conducting experiments with celestial energy. Naruto somehow gets caught in one of these experiments and as a result, he gains the starfire powers. Another possibility is that it's a gift from the stars themselves. Naruto has always been a special character, and the stars, seeing his potential and pure heart, decide to grant him these powers to help him on his journey.
One possible origin could be some kind of ancient bloodline. Maybe Naruto has a hidden bloodline that was passed down through generations and finally awakened, allowing him to summon angels. Another option is that he got this ability through a special training or a quest. He might have found a hidden place or an old sage who taught him the art of summoning angels.
One possibility is that he inherits it through some sort of bloodline connection that was previously unknown. Maybe there's a distant relative who had the ability to control sand, and it somehow got passed down to Naruto.