Often, fanfiction writers will create the origin of Hellfire Release to be linked to some ancient and powerful force. For instance, it might be related to a sealed demon or an otherworldly energy that a particular character discovers and then learns to harness as the Hellfire Release. This origin story can then be used to drive the plot forward, as other characters may seek this power or try to prevent its misuse.
One interesting storyline could be exploring the backstories of minor characters in the Naruto universe. For example, how a random villager in Konoha came to be there and their family history.
Sasuke is often popular. Fanfiction writers might explore his family's past in more detail, like how his clan was really involved in the politics of the village before their downfall.
The hypno gun in Naruto fanfic could potentially originate from a hidden village's secret research. Maybe a group of ninja scientists were trying to find a non - lethal way to subdue enemies and came up with the idea of a hypno gun.
The Raijin Sword in the fanfiction might have an ancient origin. It could be a weapon forged by a powerful ninja clan in the past. Maybe it was created to combat a great evil that once threatened the ninja world. And for some reason, it has now come into Naruto's possession.
Another possibility is that it's a gift from a powerful being. For example, a god - like entity might have bestowed the dojutsu on Naruto to help him in his journey to protect the ninja world. This often leads to Naruto having to figure out how to use it while also dealing with the expectations that come with such a powerful gift.
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.
Maybe it was some kind of experimental jutsu gone wrong or right. Some crazy scientist - type character in the Naruto universe might have been experimenting with different materials and ended up giving Naruto adamantium bones.
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.
Another possibility is that Naruto found the crow during one of his adventures. It could have been trapped or injured, and Naruto nursed it back to health. In return, the crow forms a bond with him and becomes his ally, ready to be used in his battles and quests.